We present the Hubble Catalog of Variables, the first, homogeneous catalog of variable sources created from the highly diverse, archival HST data. It is currently the deepest catalog of variables available and includes variable stars in our Galaxy and nearby galaxies, as well as transients and variable active galactic nuclei. The catalog is a valuable resource for time domain science. Possible uses include searches for new variable objects of a particular type for population analysis, detection of unique objects worthy of follow-up studies, identification of sources observed at other wavelengths, and photometric characterization of candidate progenitors of supernovae and other transients in nearby galaxies. Examples of such cases will be presented. The Hubble Catalog of Variables (HCV) is based on version 3 of the Hubble Source Catalog (HSC), which relies on publicly available images obtained with the WFPC2, ACS, and WFC3 instruments onboard the HST. It includes 84,428 candidate variable sources (out of 3.7 million HSC sources that were searched for variability) with V <= 27 mag; for 11,115 of them the variability is detected in more than one filter. The data points in the light curves of the variables in the HCV catalog range from five to 120 points (typically having less than ten points); the time baseline ranges from under a day to over 15 years; while ∼8% of all variables have amplitudes in excess of 1 mag. Visual inspection performed on a subset of the candidate variables suggests that at least 80% of the candidate variables that passed our automated quality control are true variable sources rather than spurious detections resulting from blending, residual cosmic rays, and calibration errors. The catalog is available to the community from the ESA Hubble Science Archive (eHST) at the European Space Astronomy Centre (ESAC) and the Mikulski Archive for Space Telescopes (MAST) at Space Telescope Science Institute (STScI).

Context. Gaia Early Data Release 3 (Gaia EDR3) provides accurate astrometry for about 1.6 million compact (QSO-like) extragalactic sources, 1.2 million of which have the best-quality five-parameter astrometric solutions. Aims. The proper motions of QSO-like sources are used to reveal a systematic pattern due to the acceleration of the solar system barycentre with respect to the rest frame of the Universe. Apart from being an important scientific result by itself, the acceleration measured in this way is a good quality indicator of the Gaia astrometric solution. Methods. The effect of the acceleration is obtained as a part of the general expansion of the vector field of proper motions in Vector Spherical Harmonics (VSH). Various versions of the VSH fit and various subsets of the sources are tried and compared to get the most consistent result and a realistic estimate of its uncertainty. Additional tests with the Gaia astrometric solution are used to get a better idea on possible systematic errors in the estimate. Results. Our best estimate of the acceleration based on Gaia EDR3 is $(2.32 \pm 0.16) \times 10^{-10}$ m s${}^{-2}$ (or $7.33 \pm 0.51$ km s$^{-1}$ Myr${}^{-1}$) towards $\alpha = 269.1^\circ \pm 5.4^\circ$, $\delta = -31.6^\circ \pm 4.1^\circ$, corresponding to a proper motion amplitude of $5.05 \pm 0.35$ $\mu$as yr${}^{-1}$. This is in good agreement with the acceleration expected from current models of the Galactic gravitational potential. We expect that future Gaia data releases will provide estimates of the acceleration with uncertainties substantially below 0.1 $\mu$as yr${}^{-1}$.

We compare the Gaia DR2 and Gaia EDR3 performances in the study of the Magellanic Clouds and show the clear improvements in precision and accuracy in the new release. We also show that the systematics still present in the data make the determination of the 3D geometry of the LMC a difficult endeavour; this is at the very limit of the usefulness of the Gaia EDR3 astrometry, but it may become feasible with the use of additional external data. We derive radial and tangential velocity maps and global profiles for the LMC for the several subsamples we defined. To our knowledge, this is the first time that the two planar components of the ordered and random motions are derived for multiple stellar evolutionary phases in a galactic disc outside the Milky Way, showing the differences between younger and older phases. We also analyse the spatial structure and motions in the central region, the bar, and the disc, providing new insights into features and kinematics. Finally, we show that the Gaia EDR3 data allows clearly resolving the Magellanic Bridge, and we trace the density and velocity flow of the stars from the SMC towards the LMC not only globally, but also separately for young and evolved populations. This allows us to confirm an evolved population in the Bridge that is slightly shift from the younger population. Additionally, we were able to study the outskirts of both Magellanic Clouds, in which we detected some well-known features and indications of new ones.

We produce a clean and well-characterised catalogue of objects within 100\,pc of the Sun from the \G\ Early Data Release 3. We characterise the catalogue through comparisons to the full data release, external catalogues, and simulations. We carry out a first analysis of the science that is possible with this sample to demonstrate its potential and best practices for its use. The selection of objects within 100\,pc from the full catalogue used selected training sets, machine-learning procedures, astrometric quantities, and solution quality indicators to determine a probability that the astrometric solution is reliable. The training set construction exploited the astrometric data, quality flags, and external photometry. For all candidates we calculated distance posterior probability densities using Bayesian procedures and mock catalogues to define priors. Any object with reliable astrometry and a non-zero probability of being within 100\,pc is included in the catalogue. We have produced a catalogue of \NFINAL\ objects that we estimate contains at least 92\% of stars of stellar type M9 within 100\,pc of the Sun. We estimate that 9\% of the stars in this catalogue probably lie outside 100\,pc, but when the distance probability function is used, a correct treatment of this contamination is possible. We produced luminosity functions with a high signal-to-noise ratio for the main-sequence stars, giants, and white dwarfs. We examined in detail the Hyades cluster, the white dwarf population, and wide-binary systems and produced candidate lists for all three samples. We detected local manifestations of several streams, superclusters, and halo objects, in which we identified 12 members of \G\ Enceladus. We present the first direct parallaxes of five objects in multiple systems within 10\,pc of the Sun.

Aims: We use new deep XMM-Newton observations of the northern disc of M31 to trace the hot interstellar medium (ISM) in unprecedented detail and to characterise the physical properties of the X-ray emitting plasmas. Methods: We used all XMM-Newton data up to and including our new observations to produce the most detailed image yet of the hot ISM plasma in a grand design spiral galaxy such as our own. We compared the X-ray morphology to multi-wavelength studies in the literature to set it in the context of the multi-phase ISM. We performed spectral analyses on the extended emission using our new observations as they offer sufficient depth and count statistics to constrain the plasma properties. Data from the Panchromatic Hubble Andromeda Treasury were used to estimate the energy injected by massive stars and their supernovae. We compared these results to the hot gas properties. Results: The brightest emission regions were found to be correlated with populations of massive stars, notably in the 10 kpc star-forming ring. The plasma temperatures in the ring regions are ~0.2 up to ~0.6 keV. We suggest this emission is hot ISM heated in massive stellar clusters and superbubbles. We derived X-ray luminosities, densities, and pressures for the gas in each region. We also found large extended emission filling low density gaps in the dust morphology of the northern disc, notably between the 5 and 10 kpc star-forming rings. We propose that the hot gas was heated and expelled into the gaps by the populations of massive stars in the rings. Conclusions: It is clear that the massive stellar populations are responsible for heating the ISM to X-ray emitting temperatures, filling their surroundings, and possibly driving the hot gas into the low density regions. Overall, the morphology and spectra of the hot gas in the northern disc of M31 is similar to other galaxy discs. FITS files for Figs. 1 and 2 are only available at the CDS via anonymous ftp to http://cdsarc.u-strasbg.fr (ftp://130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/cat/J/A+A/637/A12 Based on observations obtained with XMM-Newton, an ESA science mission with instruments and contributions directly funded by ESA Member States and NASA.

Figure10.4-0.7keV.fits and Figure10.7-1.25keV XMM-Newton mosaic images of M 31 in the 0.4-0.7keV and 0.7-1.25keV range. We used all XMM-Newton data up to and including our new observations (early 2016). To produce these mosaics we used the the XMM-Newton Extended Source Analysis Software (XMM-ESAS), packaged in SAS1 15.0.0. XMM-ESAS is based on the software used for the background modelling described by Snowden et al. (2004ApJ...610.1182S). The units of the images are cts/s/deg2. See Section 2.1.1 for more details. Figure2_0.4-1.25keV.fits. XMM-Newton image of the northern disk of M 31 in the 0.4-1.25keV range produced as in Figure 1. See Sections 2.1.1 and 2.2 for more details. (2 data files).

Based on observations made with the NASA/ESA Hubble Space Telescope, and obtained from the Hubble Legacy Archive, which is a collaboration between the Space Telescope Science Institute (STScI/NASA), the Space Telescope European Coordinating Facility (ST-ECF/ESA) and the Canadian Astronomy Data Centre (CADC/NRC/CSA). (1 data file).

The Hubble Source Catalog (HSC) combines lists of sources detected on images obtained with the WFPC2, ACS and WFC3 instruments aboard the Hubble Space Telescope (HST) and now available in the Hubble Legacy Archive. The catalogue contains time-domain information for about two million of its sources detected using the same instrument and filter on at least five HST visits. The Hubble Catalog of Variables (HCV) aims to identify HSC sources showing significant brightness variations. A magnitude-dependent threshold in the median absolute deviation of photometric measurements (an outlier-resistant measure of light-curve scatter) is adopted as the variability detection statistic. It is supplemented with a cut in χred2 that removes sources with large photometric errors. A pre-processing procedure involving bad image identification, outlier rejection and computation of local magnitude zero-point corrections is applied to the HSC light-curves before computing the variability detection statistics. About 52 000 HSC sources have been identified as candidate variables, among which 7,800 show variability in more than one filter. Visual inspection suggests that ~70% of the candidates detected in multiple filters are true variables, while the remaining ~30% are sources with aperture photometry corrupted by blending, imaging artefacts or image processing anomalies. The candidate variables have AB magnitudes in the range 15-27m, with a median of 22m. Among them are the stars in our own and nearby galaxies, and active galactic nuclei.

Context. Pismis 18 is a moderately populated, intermediate-age open cluster located within the solar circle at a Galactocentric distance of about seven kpc. Few open clusters have been studied in detail in the inner disc region before the Gaia-ESO Survey. Aims: New data from the Gaia-ESO Survey allowed us to conduct an extended radial velocity membership study as well as spectroscopic metallicity and detailed chemical abundance measurements for this cluster. Methods: Gaia-ESO Survey data for 142 potential members, lying on the upper main sequence and on the red clump, yielded radial velocity measurements, which, together with proper motion measurements from the Gaia Second Data Release (Gaia DR2), were used to determine the systemic velocity of the cluster and membership of individual stars. Photometry from Gaia DR2 was used to re-determine cluster parameters based on high confidence member stars only. Cluster abundance measurements of six radial-velocity member stars with UVES high-resolution spectroscopy are presented for 23 elements. Results: The average radial velocity of 26 high confidence members is -27.5 ± 2.5 (std) km s-1 with an average proper motion of pmra = -5.65 ± 0.08 (std) mas yr-1 and pmdec = -2.29 ± 0.11 (std) mas yr-1. According to the new estimates, based on high confidence members, Pismis 18 has an age of τ = 700+40-50 Myr, interstellar reddening of E(B - V) = 0.562+0.012-0.026 mag and a de-reddened distance modulus of DM0 = 11.96+0.10-0.24 mag. The median metallicity of the cluster (using the six UVES stars) is [Fe/H] = +0.23 ± 0.05 dex, with [α/Fe] = 0.07 ± 0.13 and a slight enhancement of s- and r-neutron-capture elements. Conclusions: With the present work, we fully characterized the open cluster Pismis 18. We confirmed its present location in the inner disc. We estimated a younger age than the previous literature values and we gave, for the first time, its metallicity and its detailed abundances. Its [α/Fe] and [s-process/Fe], both slightly super-solar, are in agreement with other inner-disc open clusters observed by the Gaia-ESO survey. Full Table 2 is only available at the CDS via anonymous ftp to http://cdsarc.u-strasbg.fr (ftp://130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/626/A90

We present an exceptionally deep catalog of supernovae, transients and high-amplitude variables included in the Hubble Catalog of Variables (HCV). The HCV contains all variable objects detected through a robust variability search of the light curves of all sources included in the Hubble Source Catalog version 3 (Whitmore et al. 2016). Taking this work one step further, we queried the HCV to detect all variable sources with an amplitude of variability > 1 mag, in more than one filter of observations. We cross-matched the sources with catalogs in CDS to check whether the highamplitude variable sources were previously reported. We proceeded to classify the newly identified high-amplitude variables based on their magnitude, light curve shape and position on the color magnitude diagram. The high-precision astrometry extracted from the HSC for all sources combined with the deep HST observations makes our catalog a powerful tool for further research on the environments and properties of high-amplitude variables observed by the Hubble Space Telescope. This work was supported by the European Space Agency (ESA) under the "Hubble Catalog of Variables" program, contract No. 4000112940.

The data for Pismis 18 were obtained in May and June 2014 with FLAMES on the VLT-UT2 telescope at the European Southern Observatory. (1 data file).

(Abridged) The Maunakea Spectroscopic Explorer (MSE) is an end-to-end science platform for the design, execution and scientific exploitation of spectroscopic surveys. It will unveil the composition and dynamics of the faint Universe and impact nearly every field of astrophysics across all spatial scales, from individual stars to the largest scale structures in the Universe. Major pillars in the science program for MSE include (i) the ultimate Gaia follow-up facility for understanding the chemistry and dynamics of the distant Milky Way, including the outer disk and faint stellar halo at high spectral resolution (ii) galaxy formation and evolution at cosmic noon, via the type of revolutionary surveys that have occurred in the nearby Universe, but now conducted at the peak of the star formation history of the Universe (iii) derivation of the mass of the neutrino and insights into inflationary physics through a cosmological redshift survey that probes a large volume of the Universe with a high galaxy density. MSE is positioned to become a critical hub in the emerging international network of front-line astronomical facilities, with scientific capabilities that naturally complement and extend the scientific power of Gaia, the Large Synoptic Survey Telescope, the Square Kilometer Array, Euclid, WFIRST, the 30m telescopes and many more.

Context. The ESA Gaia mission provides a unique time-domain survey for more than 1.6 billion sources with G ≲ 21 mag. Aims: We showcase stellar variability in the Galactic colour-absolute magnitude diagram (CaMD). We focus on pulsating, eruptive, and cataclysmic variables, as well as on stars that exhibit variability that is due to rotation and eclipses. Methods: We describe the locations of variable star classes, variable object fractions, and typical variability amplitudes throughout the CaMD and show how variability-related changes in colour and brightness induce "motions". To do this, we use 22 months of calibrated photometric, spectro-photometric, and astrometric Gaia data of stars with a significant parallax. To ensure that a large variety of variable star classes populate the CaMD, we crossmatched Gaia sources with known variable stars. We also used the statistics and variability detection modules of the Gaia variability pipeline. Corrections for interstellar extinction are not implemented in this article. Results: Gaia enables the first investigation of Galactic variable star populations in the CaMD on a similar, if not larger, scale as was previously done in the Magellanic Clouds. Although the observed colours are not corrected for reddening, distinct regions are visible in which variable stars occur. We determine variable star fractions to within the current detection thresholds of Gaia. Finally, we report the most complete description of variability-induced motion within the CaMD to date. Conclusions: Gaia enables novel insights into variability phenomena for an unprecedented number of stars, which will benefit the understanding of stellar astrophysics. The CaMD of Galactic variable stars provides crucial information on physical origins of variability in a way that has previously only been accessible for Galactic star clusters or external galaxies. Future Gaia data releases will enable significant improvements over this preview by providing longer time series, more accurate astrometry, and additional data types (time series BP and RP spectra, RVS spectra, and radial velocities), all for much larger samples of stars. A movie associated to Fig. 11 is available at https://www.aanda.org.Data are only available at the CDS via anonymous ftp to http://cdsarc.u-strasbg.fr (ftp://130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/623/A110.

Time series in the G, BP, and RP bands of the selected field-of-view transits for 224 sources that are not published in Gaia DR2, but are plotted in Fig. 11. An animated version of Fig. 11 is provided online and at https://www.cosmos.esa.int/web/gaia/gaiadr2_cu7. (2 data files).

We present the results of the photometric analysis of a large part of the main body of the Small Magellanic Cloud. Using the 6.5m Magellan Telescope at the Las Campanas Observatory in Chile, we have acquired deep B and I images in four fields (0.44 deg each in diameter), yielding accurate photometry for 1068 893 stars down to 24th magnitude, with a spatial resolution of 0.20 arcsec per pixel. Colour-magnitude diagrams and (completeness-corrected) luminosity functions have been constructed, yielding significant new results that indicate at least two discrete star formation events over a period from 2.7 to 4 Gyr ago. Also, we have derived star formation rates as a function of look-back time and have found enhancements of SF between 4 and 6 Gyr and at younger ages.

Aims: We use new deep XMM-Newton observations of the northern disk of M 31 to trace the hot interstellar medium (ISM) in unprecedented detail and to characterise the physical properties of the X-ray emitting plasmas. Methods: We used all XMM-Newton data up to and including our new observations to produce the most detailed image yet of the hot ISM plasma in a grand design spiral galaxy such as our own. We compared the X-ray morphology to multi-wavelength studies in the literature to set it in the context of the multi-phase ISM. We performed spectral analyses on the extended emission using our new observations as they offer sufficient depth and count statistics to constrain the plasma properties. Data from the Panchromatic Hubble Andromeda Treasury were used to estimate the energy injected by massive stars and their supernovae. We compared these results to the hot gas properties. Results: The brightest emission regions were found to be correlated with populations of massive stars, notably in the 10 kpc star-forming ring. The plasma temperatures in the ring regions are ~0.2 keV up to ~0.6 keV. We suggest this emission is hot ISM heated in massive stellar clusters and superbubbles. We derived X-ray luminosities, densities, and pressures for the gas in each region. We also found large extended emission filling low density gaps in the dust morphology of the northern disk, notably between the 5 kpc and 10 kpc star-forming rings. We propose that the hot gas was heated and expelled into the gaps by the populations of massive stars in the rings. Conclusions. It is clear that the massive stellar populations are responsible for heating the ISM to X-ray emitting temperatures, filling their surroundings, and possibly driving the hot gas into the low density regions. Overall, the morphology and spectra of the hot gas in the northern disk of M 31 is similar to other galaxy disks.

The Small Magellanic Cloud (SMC) presents us with a unique opportunity to study in detail the effect of environmental processes (interaction with the LMC and the Milky Way) on its star formation history. With the 6.5m Magellan Telescope at the Las Campanas Observatory in Chile we have acquired deep B and I images in four 0.44 degree fields covering a large part of the main body of the SMC, yielding accurate photometry for 1,068,893 stars down to ~24th magnitude, with a spatial resolution of 0.201 arcsec/pixel. Colour-magnitude diagrams and luminosity functions (corrected for completeness) have been constructed, yielding significant new results that indicate at least two discrete star formation events around 2.7 and 4-5 Gyr ago.

Aims: Over its lifetime and despite not being a survey telescope, the Hubble Space Telescope (HST) has obtained multi-epoch observations by multiple, diverse observing programs, providing the opportunity for a comprehensive variability search aiming to uncover new variables. We have therefore undertaken the task of creating a catalog of variable sources based on archival HST photometry. In particular, we have used version 3 of the Hubble Source Catalog (HSC), which relies on publicly available images obtained with the WFPC2, ACS, and WFC3 instruments onboard the HST. Methods: We adopted magnitude-dependent thresholding in median absolute deviation (a robust measure of light curve scatter) combined with sophisticated preprocessing techniques and visual quality control to identify and validate variable sources observed by Hubble with the same instrument and filter combination five or more times. Results: The Hubble Catalog of Variables (HCV) includes 84 428 candidate variable sources (out of 3.7 million HSC sources that were searched for variability) with V ≤ 27 mag; for 11 115 of them the variability is detected in more than one filter. The data points in the light curves of the variables in the HCV catalog range from five to 120 points (typically having less than ten points); the time baseline ranges from under a day to over 15 years; while ˜8% of all variables have amplitudes in excess of 1 mag. Visual inspection performed on a subset of the candidate variables suggests that at least 80% of the candidate variables that passed our automated quality control are true variable sources rather than spurious detections resulting from blending, residual cosmic rays, and calibration errors. Conclusion. The HCV is the first, homogeneous catalog of variable sources created from the highly diverse, archival HST data and currently is the deepest catalog of variables available. The catalog includes variable stars in our Galaxy and nearby galaxies, as well as transients and variable active galactic nuclei. We expect that the catalog will be a valuable resource for the community. Possible uses include searches for new variable objects of a particular type for population analysis, detection of unique objects worthy of follow-up studies, identification of sources observed at other wavelengths, and photometric characterization of candidate progenitors of supernovae and other transients in nearby galaxies. The catalog is available to the community from the ESA Hubble Science Archive (eHST) at the European Space Astronomy Centre (ESAC) and the Mikulski Archive for Space Telescopes (MAST) at Space Telescope Science Institute (STScI). Full Tables B.2 and B.3 are only available at the CDS via anonymous ftp to http://cdsarc.u-strasbg.fr (ftp://130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/cat/J/A+A/630/A92

Studies of the massive star population in galaxies beyond the Local Group are the key to understanding the link between their numbers and modes of star formation in different environments. We present the analysis of the massive star population of the galaxies NGC 1326A, NGC 1425, and NGC 4548 using archival images obtained with the Hubble Space Telescope Wide Field Planetary Camera 2 in the F555W and F814W filters. Through high-precision point spread function fitting photometry for all sources in the three fields, we identified 7640 candidate blue supergiants, 2314 candidate yellow supergiants, and 4270 candidate red supergiants. We provide an estimate of the ratio of blue to red supergiants for each field as a function of galactocentric radius. Using Modules for Experiments in Stellar Astrophysics (MESA) at solar metallicity, we defined the luminosity function and estimated the star formation history of each galaxy. We carried out a variability search in the V and I filters using three variability indexes: the median absolute deviation, the interquartile range, and the inverse von Neumann ratio. This analysis yielded 243 new variable candidates with absolute magnitudes ranging from MV = -4 to -10 mag. We classified the variable stars based on their absolute magnitude and their position on the color-magnitude diagram using the MESA evolutionary tracks at solar metallicity. Our analysis yielded 8 candidate variable blue supergiants, 12 candidate variable yellow supergiants, 21 candidate variable red supergiants, and 4 candidate periodic variables. Full Tables 1, 2, 3, and Tables 6-10 are only available at the CDS via anonymous ftp to http://cdsarc.u-strasbg.fr (ftp://130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/629/A3

We propose 200 ks total ACIS-S observations of the spiral galaxy NGC 2336, one of the most actively star-forming galaxies in the local Universe. The proposed observations will reach Lx 7 x 10^{37} erg/s, yielding over 40 high-mass X-ray binaries (XRBs). Archival UV data and supporting Hubble Space Telescope observations fully leverage our proposed Chandra observations by allowing us to: (a) measure the age and metallicity distribution of young XRBs; (b) measure the formation efficiency of young XRBs as a function of the age of their parent stellar populations; (c) constrain XRB formation models; (d) characterize the ultra-luminous XRB population; (e) explore the role of star formation in energizing the ISM; and (f) identify the nature of the nuclear source.

Identifying active galactic nuclei (AGNs) through their X-ray emission is efficient, but necessarily biased against X-ray-faint objects. We aim to characterize this bias by comparing X-ray-selected AGNs to the ones identified through optical variability and mid-infrared (mid-IR) colours. We present a catalogue of AGNs selected through optical variability using all publicly available z-band Hubble Space Telescope images in the GOODS-South field. For all objects in the catalogue, we compute X-ray upper limits or discuss detections in the deepest available ˜7 Ms Chandra Deep Field South images and present the Spitzer/Infrared Array Camera (IRAC) mid-IR colours. For the variability study, we consider only sources observed over at least five epochs and over a time baseline of up to 10 yr. We adopt the elevated median absolute deviation as a variability indicator robust against individual outlier measurements and identify 113 variability-selected AGN candidates. Among these, 26 have an X-ray counterpart and lie within the conventional AGN area in the FX/Fopt diagram. The candidates with X-ray upper limits are on average optically fainter, have higher redshifts compared to the X-ray-detected ones and are consistent with low-luminosity AGNs. Out of 41 variable optical sources with IR detections, 13 fulfill the IR AGN colour selection criteria. Our work emphasizes the importance of optical variability surveys for constructing complete samples of AGNs including the ones that remain undetected even by the deepest X-ray and IR surveys.

We used archival observations of NGC 1326A, NGC 1425, and NGC 4548 taken with the HST WFPC2 as described in Freedman et al. (2001ApJ...553...47F) as part of the HST Key Project. For the three galaxies, we used the observations available in the filters F555W(equivalent to Johnson V filter) and the F814W (equivalent toKron-Cousins I). In particular, we used 13 epochs of observations in F555W and 8 epochs in F814W that are available for the galaxies NGC 1326A and NGC 4548, while for NGC 1425, we used the 14 available epochs in F555W and 8 in F814W (6 data files).

The HCV catalog (tableb2) lists for each source the equatorial coordinates, MatchID, GroupID, subgroup, the pipeline classification flag, the expert-validation classification flag, the number of existing instrument and filter combinations for the source, the name of the instrument and filter combination for which the following data are given: the filter detection flag, which indicates whether the source is variable [1] or is not variable [0], the variability quality flag, the number of measurements in the light curve, the HSC magnitude, the corrected magnitude, the MAD value, and the reduced chi2 value. For all multi-filter variable candidates, there are extra columns for each additional instrument and filter combination, in which the source is classified as a variable candidate. The catalog of constant sources (tableb3) contains the sources that fall below the 5σ detection threshold of the HCV pipeline. These include constant sources and possibly, low-amplitude variables below the detection threshold. For each source, the columns show the equatorial coordinates, the MatchID, the GroupID, the subgroup, the number of instrument and filter combinations in which individual sources are observed, followed by the name of each instrument and filter combination for which the following data are given: the number of measurements in the light curve, the HSC magnitude, the corrected magnitude, the MAD value, and the reduced chi2 value. (2 data files).

Almost all confirmed optical counterparts of HMXBs in the SMC are OB stars with equatorial decretion disks (OBe). These sources emit strongly in Balmer lines and standout when imaged through narrow-band Hα imaging. The lack of secure counterparts for a significant fraction of the HMXBs motivated us to search for more. Using the catalogs for OB/OBe stars (Maravelias et al. 2017) and for HMXBs (Haberl & Sturm 2016) we detect 70 optical counterparts (out of 104 covered by our survey). We provide the first identification of the optical counterpart to the source XTEJ0050-731. We verify that 17 previously uncertain optical counterparts are indeed the proper matches. Regarding 52 confirmed HMXBs (known optical counterparts with Hα emission), we detect 39 as OBe and another 13 as OB stars. This allows a direct estimation of the fraction of active OBe stars in HMXBs that show Hα emission at a given epoch to be at least ˜75% of their total HMXB population.

We analyzed the massive star population of the Virgo Cluster galaxy NGC 4535 using archival Hubble Space Telescope Wide Field Planetary Camera 2 images in filters F555W and F814W, equivalent to Johnson V and Kron-Cousins I. We performed high precision point spread function fitting photometry of 24353 sources including 3762 candidate blue supergiants, 841 candidate yellow supergiants and 370 candidate red supergiants. We estimated the ratio of blue to red supergiants as a decreasing function of galactocentric radius. Using Modules for Experiments in Stellar Astrophysics isochrones at solar metallicity, we defined the luminosity function and estimated the star formation history of the galaxy over the last 60 Myrs. We conducted a variability search in the V and I filters using three variability indexes: the median absolute deviation, the interquartile range and the inverse von-Neumann ratio. This analysis yielded 120 new variable candidates with absolute magnitudes ranging from M$_{V}$ = $-$4 to $-$11 mag. We used the MESA evolutionary tracks at solar metallicity, to classify the variables based on their absolute magnitude and their position on the color-magnitude diagram. Among the new candidate variable sources are eight candidate variable red supergiants, three candidate variable yellow supergiants and one candidate luminous blue variable, which we suggest for follow-up observations.

Principal component analysis (PCA) is being extensively used in Astronomy but not yet exhaustively exploited for variability search. The aim of this work is to investigate the effectiveness of using the PCA as a method to search for variable stars in large photometric data sets. We apply PCA to variability indices computed for light curves of 18 152 stars in three fields in M 31 extracted from the Hubble Source Catalogue. The projection of the data into the principal components is used as a stellar variability detection and classification tool, capable of distinguishing between RR Lyrae stars, long-period variables (LPVs) and non-variables. This projection recovered more than 90 per cent of the known variables and revealed 38 previously unknown variable stars (about 30 per cent more), all LPVs except for one object of uncertain variability type. We conclude that this methodology can indeed successfully identify candidate variable stars.

We have determined the membership of 46 open clusters. For the nine clusters within 250pc we determined optimised parallaxes based on the combined information extracted from the measured parallax and proper motion values. These clusters are : in Tables A1a & A3: alphaPer, Blanco1, ComaBer, Hyades, IC2391, IC2602, NGC2451A, Pleiades, Praesepe. The remaining 37 clusters are in Table A1b & A4: Coll140, IC4651, IC4665, IC4725, IC4756, NGC0188, NGC0752, NGC0869, NGC0884, NGC1039, NGC1901, NGC2158, NGC2168, NGC2232, NGC2323, NGC2360, NGC2422, NGC2423, NGC2437, NGC2447, NGC2516, NGC2547, NGC2548, NGC2682, NGC3228, NGC3532, NGC6025, NGC6281, NGC6405, NGC6475, NGC6633, NGC6774, NGC6793, NGC7092, Stock2, Trump02, Trump10. (4 data files).

Our analysis was performed on the iDR4 consisting of ~260000 single exposures (corresponding to ~100 000 stacked spectra) of about 51000 distinct stars observed with the FLAMES instrument feeding the optical spectrographs GIRAFFE (with setups HR3, HR5A, HR6, HR9B, HR10, HR14A, HR15N, HR15, HR21) and UVES (with setups U520 and U580) covering the optical and near-IR wavelength ranges. (5 data files).

Context. We carried out new observations of two fields in the star-forming northern ring of M 31 with XMM-Newton with each one of them consisting of two exposures of about 100 ks each. A previous XMM-Newton survey of the entire M 31 galaxy revealed extended diffuse X-ray emission in these regions. Aims: We study the population of X-ray sources in the northern disc of M 31 by compiling a complete list of X-ray sources down to a sensitivity limit of ∼7 × 1034 erg s-1 (0.5-2.0 keV) and improve the identification of the X-ray sources. The major objective of the observing programme was the study of the hot phase of the interstellar medium (ISM) in M 31. The analysis of the diffuse emission and the study of the ISM is presented in a separate paper. Methods: We analysed the spectral properties of all detected sources using hardness ratios and spectra if the statistics were high enough. We also checked for variability. In order to classify the sources detected in the new deep XMM-Newton observations, we cross-correlated the source list with the source catalogue of a new survey of the northern disc of M 31 carried out with the Chandra X-ray Observatory and the Hubble Space Telescope (Panchromatic Hubble Andromeda Treasury, PHAT) as well as with other existing catalogues. Results: We detected a total of 389 sources in the two fields of the northern disc of M 31 observed with XMM-Newton. We identified 43 foreground stars and candidates and 50 background sources. Based on a comparison with the results of the Chandra/PHAT survey, we classify 24 hard X-ray sources as new candidates for X-ray binaries. In total, we identified 34 X-ray binaries and candidates and 18 supernova remnants (SNRs) and candidates. We studied the spectral properties of the four brightest SNRs and confirmed five new X-ray SNRs. Three of the four SNRs, for which a spectral analysis was performed, show emission mainly below 2 keV, which is consistent with shocked ISM. The spectra of two of them also require an additional component with a higher temperature. The SNR [SPH11] 1535 has a harder spectrum and might suggest that there is a pulsar-wind nebula inside the SNR. For all SNRs in the observed fields, we measured the X-ray flux or calculated upper limits. We also carried out short-term and long-term variability studies of the X-ray sources and found five new sources showing clear variability. In addition, we studied the spectral properties of the transient source SWIFT J004420.1+413702, which shows significant variation in flux over a period of seven months (June 2015 to January 2016) and associated change in absorption. Based on the likely optical counterpart detected in the Chandra/PHAT survey, the source is classified as a low-mass X-ray binary. Based on observations obtained with XMM-Newton, an ESA science mission with instruments and contributions directly funded by ESA Member States and NASA.Tables A.1-A.6 are only available at the CDS via anonymous ftp to http://cdsarc.u-strasbg.fr (ftp://130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/620/A28

We analyzed the massive star population of the Virgo Cluster galaxy NGC 4535 using archival Hubble Space Telescope Wide Field Planetary Camera 2 images in filters F555W and F814W, equivalent to Johnson V and Kron-Cousins I. We performed high precision point spread function fitting photometry of 24353 sources including 3762 candidate blue supergiants, 841 candidate yellow supergiants, and 370 candidate red supergiants. We estimated the ratio of blue to red supergiants as a decreasing function of galactocentric radius. Using Modules for Experiments in Stellar Astrophysics (MESA) isochrones at solar metallicity, we defined the luminosity function and estimated the star formation history of the galaxy over the last 60 Myr. We conducted a variability search in the V and I filters using three variability indexes: the median absolute deviation, the interquartile range, and the inverse von-Neumann ratio. This analysis yielded 120 new variable candidates with absolute magnitudes ranging from MV = -4 to -11 mag. We used the MESA evolutionary tracks at solar metallicity to classify the variables based on their absolute magnitude and their position on the color-magnitude diagram. Among the new candidate variable sources are eight candidate variable red supergiants, three candidate variable yellow supergiants and one candidate luminous blue variable, which we suggest for follow-up observations. Full Table A.1 is only available at the CDS via anonymous ftp to http://cdsarc.u-strasbg.fr (ftp://130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/618/A185

We have observed two fields in the northern disc of M31 in a large programme (LP) of XMM-Newton (PI: M. Sasaki). The data were taken with the European Photon Imaging Cameras (EPICs) in full-frame mode using the thin filter for the pn camera (EPIC-pn) and the medium filter for the two MOS cameras (EPIC-MOS1/2), in order to minimise the contamination by background but to maximise the sensitivity for soft diffuse emission. Each of the two fields was observed twice. (6 data files).

Context. The second Gaia data release (Gaia DR2) contains high-precision positions, parallaxes, and proper motions for 1.3 billion sources as well as line-of-sight velocities for 7.2 million stars brighter than GRVS = 12 mag. Both samples provide a full sky coverage. Aims: To illustrate the potential of Gaia DR2, we provide a first look at the kinematics of the Milky Way disc, within a radius of several kiloparsecs around the Sun. Methods: We benefit for the first time from a sample of 6.4 million F-G-K stars with full 6D phase-space coordinates, precise parallaxes (σϖ/ϖ ≤ 20%), and precise Galactic cylindrical velocities (median uncertainties of 0.9-1.4 km s-1 and 20% of the stars with uncertainties smaller than 1 km s-1 on all three components). From this sample, we extracted a sub-sample of 3.2 million giant stars to map the velocity field of the Galactic disc from 5 kpc to 13 kpc from the Galactic centre and up to 2 kpc above and below the plane. We also study the distribution of 0.3 million solar neighbourhood stars (r < 200 pc), with median velocity uncertainties of 0.4 km s-1, in velocity space and use the full sample to examine how the over-densities evolve in more distant regions. Results: Gaia DR2 allows us to draw 3D maps of the Galactocentric median velocities and velocity dispersions with unprecedented accuracy, precision, and spatial resolution. The maps show the complexity and richness of the velocity field of the galactic disc. We observe streaming motions in all the components of the velocities as well as patterns in the velocity dispersions. For example, we confirm the previously reported negative and positive galactocentric radial velocity gradients in the inner and outer disc, respectively. Here, we see them as part of a non-axisymmetric kinematic oscillation, and we map its azimuthal and vertical behaviour. We also witness a new global arrangement of stars in the velocity plane of the solar neighbourhood and in distant regions in which stars are organised in thin substructures with the shape of circular arches that are oriented approximately along the horizontal direction in the U - V plane. Moreover, in distant regions, we see variations in the velocity substructures more clearly than ever before, in particular, variations in the velocity of the Hercules stream. Conclusions: Gaia DR2 provides the largest existing full 6D phase-space coordinates catalogue. It also vastly increases the number of available distances and transverse velocities with respect to Gaia DR1. Gaia DR2 offers a great wealth of information on the Milky Way and reveals clear non-axisymmetric kinematic signatures within the Galactic disc, for instance. It is now up to the astronomical community to explore its full potential.

Context. Gaia Data Release 2 provides high-precision astrometry and three-band photometry for about 1.3 billion sources over the full sky. The precision, accuracy, and homogeneity of both astrometry and photometry are unprecedented. Aims: We highlight the power of the Gaia DR2 in studying many fine structures of the Hertzsprung-Russell diagram (HRD). Gaia allows us to present many different HRDs, depending in particular on stellar population selections. We do not aim here for completeness in terms of types of stars or stellar evolutionary aspects. Instead, we have chosen several illustrative examples. Methods: We describe some of the selections that can be made in Gaia DR2 to highlight the main structures of the Gaia HRDs. We select both field and cluster (open and globular) stars, compare the observations with previous classifications and with stellar evolutionary tracks, and we present variations of the Gaia HRD with age, metallicity, and kinematics. Late stages of stellar evolution such as hot subdwarfs, post-AGB stars, planetary nebulae, and white dwarfs are also analysed, as well as low-mass brown dwarf objects. Results: The Gaia HRDs are unprecedented in both precision and coverage of the various Milky Way stellar populations and stellar evolutionary phases. Many fine structures of the HRDs are presented. The clear split of the white dwarf sequence into hydrogen and helium white dwarfs is presented for the first time in an HRD. The relation between kinematics and the HRD is nicely illustrated. Two different populations in a classical kinematic selection of the halo are unambiguously identified in the HRD. Membership and mean parameters for a selected list of open clusters are provided. They allow drawing very detailed cluster sequences, highlighting fine structures, and providing extremely precise empirical isochrones that will lead to more insight in stellar physics. Conclusions: Gaia DR2 demonstrates the potential of combining precise astrometry and photometry for large samples for studies in stellar evolution and stellar population and opens an entire new area for HRD-based studies. The full Table A.1 is only available at the CDS via anonymous ftp to http://cdsarc.u-strasbg.fr (http://130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/616/A10

Context. The Gaia spacecraft of the European Space Agency (ESA) has been securing observations of solar system objects (SSOs) since the beginning of its operations. Data Release 2 (DR2) contains the observations of a selected sample of 14,099 SSOs. These asteroids have been already identified and have been numbered by the Minor Planet Center repository. Positions are provided for each Gaia observation at CCD level. As additional information, complementary to astrometry, the apparent brightness of SSOs in the unfiltered G band is also provided for selected observations. Aims: We explain the processing of SSO data, and describe the criteria we used to select the sample published in Gaia DR2. We then explore the data set to assess its quality. Methods: To exploit the main data product for the solar system in Gaia DR2, which is the epoch astrometry of asteroids, it is necessary to take into account the unusual properties of the uncertainty, as the position information is nearly one-dimensional. When this aspect is handled appropriately, an orbit fit can be obtained with post-fit residuals that are overall consistent with the a-priori error model that was used to define individual values of the astrometric uncertainty. The role of both random and systematic errors is described. The distribution of residuals allowed us to identify possible contaminants in the data set (such as stars). Photometry in the G band was compared to computed values from reference asteroid shapes and to the flux registered at the corresponding epochs by the red and blue photometers (RP and BP). Results: The overall astrometric performance is close to the expectations, with an optimal range of brightness G 12 - 17. In this range, the typical transit-level accuracy is well below 1 mas. For fainter asteroids, the growing photon noise deteriorates the performance. Asteroids brighter than G 12 are affected by a lower performance of the processing of their signals. The dramatic improvement brought by Gaia DR2 astrometry of SSOs is demonstrated by comparisons to the archive data and by preliminary tests on the detection of subtle non-gravitational effects.

Context. We present the second Gaia data release, Gaia DR2, consisting of astrometry, photometry, radial velocities, and information on astrophysical parameters and variability, for sources brighter than magnitude 21. In addition epoch astrometry and photometry are provided for a modest sample of minor planets in the solar system. Aims: A summary of the contents of Gaia DR2 is presented, accompanied by a discussion on the differences with respect to Gaia DR1 and an overview of the main limitations which are still present in the survey. Recommendations are made on the responsible use of Gaia DR2 results. Methods: The raw data collected with the Gaia instruments during the first 22 months of the mission have been processed by the Gaia Data Processing and Analysis Consortium (DPAC) and turned into this second data release, which represents a major advance with respect to Gaia DR1 in terms of completeness, performance, and richness of the data products. Results: Gaia DR2 contains celestial positions and the apparent brightness in G for approximately 1.7 billion sources. For 1.3 billion of those sources, parallaxes and proper motions are in addition available. The sample of sources for which variability information is provided is expanded to 0.5 million stars. This data release contains four new elements: broad-band colour information in the form of the apparent brightness in the GBP (330-680 nm) and GRP (630-1050 nm) bands is available for 1.4 billion sources; median radial velocities for some 7 million sources are presented; for between 77 and 161 million sources estimates are provided of the stellar effective temperature, extinction, reddening, and radius and luminosity; and for a pre-selected list of 14 000 minor planets in the solar system epoch astrometry and photometry are presented. Finally, Gaia DR2 also represents a new materialisation of the celestial reference frame in the optical, the Gaia-CRF2, which is the first optical reference frame based solely on extragalactic sources. There are notable changes in the photometric system and the catalogue source list with respect to Gaia DR1, and we stress the need to consider the two data releases as independent. Conclusions: Gaia DR2 represents a major achievement for the Gaia mission, delivering on the long standing promise to provide parallaxes and proper motions for over 1 billion stars, and representing a first step in the availability of complementary radial velocity and source astrophysical information for a sample of stars in the Gaia survey which covers a very substantial fraction of the volume of our galaxy.

Context. The second release of Gaia data (Gaia DR2) contains the astrometric parameters for more than half a million quasars. This set defines a kinematically non-rotating reference frame in the optical domain. A subset of these quasars have accurate VLBI positions that allow the axes of the reference frame to be aligned with the International Celestial Reference System (ICRF) radio frame. Aims: We describe the astrometric and photometric properties of the quasars that were selected to represent the celestial reference frame of Gaia DR2 (Gaia-CRF2), and to compare the optical and radio positions for sources with accurate VLBI positions. Methods: Descriptive statistics are used to characterise the overall properties of the quasar sample. Residual rotation and orientation errors and large-scale systematics are quantified by means of expansions in vector spherical harmonics. Positional differences are calculated relative to a prototype version of the forthcoming ICRF3. Results: Gaia-CRF2 consists of the positions of a sample of 556 869 sources in Gaia DR2, obtained from a positional cross-match with the ICRF3-prototype and AllWISE AGN catalogues. The sample constitutes a clean, dense, and homogeneous set of extragalactic point sources in the magnitude range G ≃ 16 to 21 mag with accurately known optical positions. The median positional uncertainty is 0.12 mas for G < 18 mag and 0.5 mas at G = mag. Large-scale systematics are estimated to be in the range 20 to 30 μas. The accuracy claims are supported by the parallaxes and proper motions of the quasars in Gaia DR2. The optical positions for a subset of 2820 sources in common with the ICRF3-prototype show very good overall agreement with the radio positions, but several tens of sources have significantly discrepant positions. Conclusions: Based on less than 40% of the data expected from the nominal Gaia mission, Gaia-CRF2 is the first realisation of a non-rotating global optical reference frame that meets the ICRS prescriptions, meaning that it is built only on extragalactic sources. Its accuracy matches the current radio frame of the ICRF, but the density of sources in all parts of the sky is much higher, except along the Galactic equator.

We used archival observations of NGC 4535 taken with the HST WFPC2 as part of the HST Key Project. We used 13 epochs of F555W (equivalent to Johnson V) and 9 epochs of F814W (equivalent to Kron-Cousins I). The F555W data consisted in total of eight 3x1200 sec exposures and five 4x1300s exposures, while the F814W of nine 3x1300s exposures. (1 data file).

In ATel #12224 we reported the H & alpha; emission, derived from a wide-field photometric survey of the Small Magellanic Cloud (Maravelias et al. 2017, IAUS 329, 373; Maravelias et al. 2019, in prep.), of the proposed optical counterpart source [M2002] 20671 to the X-ray transient XTE J0052-723 pulsar (SXP 4.78; Swift J005139.2-721704; ATel #12209).

The Hubble Catalog of Variables (HCV) project aims to identify the variable sources in the Hubble Source Catalog (HSC), which includes about 92 million objects with over 300 million measurements detected by the WFPC2, ACS and WFC3 cameras on board of the Hubble Space Telescope (HST), by using an automated pipeline containing a set of detection and validation algorithms. All the HSC sources with more than a predefined number of measurements in a single filter/instrument combination are pre-processed to correct systematic effects and to remove bad measurements. The corrected data are used to compute a number of variability indexes to determine the variability status of each source. The final variable source catalog will contain variable stars, active galactic nuclei (AGNs), supernovae (SNs) or even new types of variables, reaching an unprecedented depth (V≤27 mag). At the end of the project, the first release of the HCV will be available at the Mikulski Archive for Space Telescopes (MAST) and the ESA Hubble Science Archives. The HCV pipeline will be deployed at the Space Telescope Science Institute (STScI) so that an updated HCV may be generated following future releases of the HSC.

ATel #12209 reported the detection of a new X-ray transient in the Small Magellanic Cloud (SMC), Swift J005139.2-721704, exhibiting outbursting activity. The system has been classified as a new SMC high-mass X-ray binary based on its identification with the B-type star [M2002]20671.

Context. Parallaxes for 331 classical Cepheids, 31 Type II Cepheids, and 364 RR Lyrae stars in common between Gaia and the HIPPARCOS and Tycho-2 catalogues are published in Gaia Data Release 1 (DR1) as part of the Tycho-Gaia Astrometric Solution (TGAS). Aims: In order to test these first parallax measurements of the primary standard candles of the cosmological distance ladder, which involve astrometry collected by Gaia during the initial 14 months of science operation, we compared them with literature estimates and derived new period-luminosity (PL), period-Wesenheit (PW) relations for classical and Type II Cepheids and infrared PL, PL-metallicity (PLZ), and optical luminosity-metallicity (MV-[Fe/H]) relations for the RR Lyrae stars, with zero points based on TGAS. Methods: Classical Cepheids were carefully selected in order to discard known or suspected binary systems. The final sample comprises 102 fundamental mode pulsators with periods ranging from 1.68 to 51.66 days (of which 33 with σϖ/ϖ< 0.5). The Type II Cepheids include a total of 26 W Virginis and BL Herculis stars spanning the period range from 1.16 to 30.00 days (of which only 7 with σϖ/ϖ< 0.5). The RR Lyrae stars include 200 sources with pulsation period ranging from 0.27 to 0.80 days (of which 112 with σϖ/ϖ< 0.5). The new relations were computed using multi-band (V,I,J,Ks) photometry and spectroscopic metal abundances available in the literature, and by applying three alternative approaches: (i) linear least-squares fitting of the absolute magnitudes inferred from direct transformation of the TGAS parallaxes; (ii) adopting astrometry-based luminosities; and (iii) using a Bayesian fitting approach. The last two methods work in parallax space where parallaxes are used directly, thus maintaining symmetrical errors and allowing negative parallaxes to be used. The TGAS-based PL,PW,PLZ, and MV- [Fe/H] relations are discussed by comparing the distance to the Large Magellanic Cloud provided by different types of pulsating stars and alternative fitting methods. Results: Good agreement is found from direct comparison of the parallaxes of RR Lyrae stars for which both TGAS and HST measurements are available. Similarly, very good agreement is found between the TGAS values and the parallaxes inferred from the absolute magnitudes of Cepheids and RR Lyrae stars analysed with the Baade-Wesselink method. TGAS values also compare favourably with the parallaxes inferred by theoretical model fitting of the multi-band light curves for two of the three classical Cepheids and one RR Lyrae star, which were analysed with this technique in our samples. The K-band PL relations show the significant improvement of the TGAS parallaxes for Cepheids and RR Lyrae stars with respect to the HIPPARCOS measurements. This is particularly true for the RR Lyrae stars for which improvement in quality and statistics is impressive. Conclusions: TGAS parallaxes bring a significant added value to the previous HIPPARCOS estimates. The relations presented in this paper represent the first Gaia-calibrated relations and form a work-in-progress milestone report in the wait for Gaia-only parallaxes of which a first solution will become available with Gaia Data Release 2 (DR2) in 2018. Full Tables A.1-A.3 are only available at the CDS via anonymous ftp to http://cdsarc.u-strasbg.fr (http://130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/605/A79

The Hubble Catalog of Variables (HCV) is a 3 year ESA funded project that aims to develop a set of algorithms to identify variables among the sources included in the Hubble Source Catalog (HSC) and produce the HCV. We will process all HSC sources with more than a predefined number of measurements in a single filter/instrument combination and compute a range of lightcurve features to determine the variability status of each source. At the end of the project, the first release of the Hubble Catalog of Variables will be made available at the Mikulski Archive for Space Telescopes (MAST) and the ESA Science Archives. The variability detection pipeline will be implemented at the Space Telescope Science Institute (STScI) so that updated versions of the HCV may be created following the future releases of the HSC.

Context. The first Gaia Data Release contains the Tycho-Gaia Astrometric Solution (TGAS). This is a subset of about 2 million stars for which, besides the position and photometry, the proper motion and parallax are calculated using HIPPARCOS and Tycho-2 positions in 1991.25 as prior information. Aims: We investigate the scientific potential and limitations of the TGAS component by means of the astrometric data for open clusters. Methods: Mean cluster parallax and proper motion values are derived taking into account the error correlations within the astrometric solutions for individual stars, an estimate of the internal velocity dispersion in the cluster, and, where relevant, the effects of the depth of the cluster along the line of sight. Internal consistency of the TGAS data is assessed. Results: Values given for standard uncertainties are still inaccurate and may lead to unrealistic unit-weight standard deviations of least squares solutions for cluster parameters. Reconstructed mean cluster parallax and proper motion values are generally in very good agreement with earlier HIPPARCOS-based determination, although the Gaia mean parallax for the Pleiades is a significant exception. We have no current explanation for that discrepancy. Most clusters are observed to extend to nearly 15 pc from the cluster centre, and it will be up to future Gaia releases to establish whether those potential cluster-member stars are still dynamically bound to the clusters. Conclusions: The Gaia DR1 provides the means to examine open clusters far beyond their more easily visible cores, and can provide membership assessments based on proper motions and parallaxes. A combined HR diagram shows the same features as observed before using the HIPPARCOS data, with clearly increased luminosities for older A and F dwarfs. Tables D.1 to D.19 are also available at the CDS via anonymous ftp to http://cdsarc.u-strasbg.fr (http://130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/601/A19

Data for GES are taken with the Fiber Large Array Multi-Element Spectrograph (FLAMES) on the VLT at the European Southern Observatory. FLAMES has two instruments, the medium-resolution multi-object spectrograph GIRAFFE and the high-resolution Ultraviolet and Visual Echelle Spectrograph (UVES). For intermediate-age OCs with prominent red clumps, GES targets are selected as follows: likely clump stars are observed with UVES, so that the most time-intensive targets are most likely to be members, followed by probable red giants if the clump is sparse. Main sequence stars down to V=19 are observed with GIRAFFE, using the HR9B setup primarily for stars of spectral type A to F and the HR15N setup for cooler stars. General GES target selection methods are outlined in Bragaglia et al. (in prep.). (6 data files).

We have determined and examined the astrometric data for 19 open clusters, ranging from the Hyades at just under 47pc to NGC 2422 at nearly 440pc. The clusters are : the Hyades, Coma Berenices, the Pleiades, Praesepe, alpha Per, IC 2391, IC 2602, Blanco 1, NGC 2451, NGC 6475, NGC 7092, NGC 2516, NGC 2232, IC 4665, NGC 6633, Collinder 140, NGC 2422, NGC 3532 and NGC 2547. (2 data files).

Context. Trumpler 23 is a moderately populated, intermediate-age open cluster within the solar circle at a RGC 6 kpc. It is in a crowded field very close to the Galactic plane and the color-magnitude diagram shows significant field contamination and possible differential reddening; it is a relatively understudied cluster for these reasons, but its location makes it a key object for determining Galactic abundance distributions. Aims: New data from the Gaia-ESO Survey enable the first ever radial velocity and spectroscopic metallicity measurements for this cluster. We aim to use velocities to isolate cluster members, providing more leverage for determining cluster parameters. Methods: Gaia-ESO Survey data for 167 potential members have yielded radial velocity measurements, which were used to determine the systemic velocity of the cluster and membership of individual stars. Atmospheric parameters were also used as a check on membership when available. Literature photometry was used to re-determine cluster parameters based on radial velocity member stars only; theoretical isochrones are fit in the V, V-I diagram. Cluster abundance measurements of ten radial-velocity member stars with high-resolution spectroscopy are presented for 24 elements. These abundances have been compared to local disk stars, and where possible placed within the context of literature gradient studies. Results: We find Trumpler 23 to have an age of 0.80 ± 0.10 Gyr, significant differential reddening with an estimated mean cluster E(V-I) of 1.02, and an apparent distance modulus of 14.15 ± 0.20. We find an average cluster metallicity of [Fe/H] = 0.14 ± 0.03 dex, a solar [α/Fe] abundance, and notably subsolar [s-process/Fe] abundances.

Photometric measurements are prone to systematic errors presenting a challenge to low-amplitude variability detection. In search for a general-purpose variability detection technique able to recover a broad range of variability types including currently unknown ones, we test 18 statistical characteristics quantifying scatter and/or correlation between brightness measurements. We compare their performance in identifying variable objects in seven time series data sets obtained with telescopes ranging in size from a telephoto lens to 1 m-class and probing variability on time-scales from minutes to decades. The test data sets together include light curves of 127 539 objects, among them 1251 variable stars of various types and represent a range of observing conditions often found in ground-based variability surveys. The real data are complemented by simulations. We propose a combination of two indices that together recover a broad range of variability types from photometric data characterized by a wide variety of sampling patterns, photometric accuracies and percentages of outlier measurements. The first index is the interquartile range (IQR) of magnitude measurements, sensitive to variability irrespective of a time-scale and resistant to outliers. It can be complemented by the ratio of the light-curve variance to the mean square successive difference, 1/η, which is efficient in detecting variability on time-scales longer than the typical time interval between observations. Variable objects have larger 1/η and/or IQR values than non-variable objects of similar brightness. Another approach to variability detection is to combine many variability indices using principal component analysis. We present 124 previously unknown variable stars found in the test data.

Context. The Gaia-ESO Survey (GES) is a large spectroscopic survey that provides a unique opportunity to study the distribution of spectroscopic multiple systems among different populations of the Galaxy. Aims: Our aim is to detect binarity/multiplicity for stars targeted by the GES from the analysis of the cross-correlation functions (CCFs) of the GES spectra with spectral templates. Methods: We developed a method based on the computation of the CCF successive derivatives to detect multiple peaks and determine their radial velocities, even when the peaks are strongly blended. The parameters of the detection of extrema (DOE) code have been optimized for each GES GIRAFFE and UVES setup to maximize detection. The DOE code therefore allows to automatically detect multiple line spectroscopic binaries (SBn, n ≥ 2). Results: We apply this method on the fourth GES internal data release and detect 354 SBn candidates (342 SB2, 11 SB3, and even one SB4), including only nine SBs known in the literature. This implies that about 98% of these SBn candidates are new because of their faint visual magnitude that can reach V = 19. Visual inspection of the SBn candidate spectra reveals that the most probable candidates have indeed a composite spectrum. Among the SB2 candidates, an orbital solution could be computed for two previously unknown binaries: CNAME 06404608+0949173 (known as V642 Mon) in NGC 2264 and CNAME 19013257-0027338 in Berkeley 81 (Be 81). A detailed analysis of the unique SB4 (four peaks in the CCF) reveals that CNAME 08414659-5303449 (HD 74438) in the open cluster IC 2391 is a physically bound stellar quadruple system. The SB candidates belonging to stellar clusters are reviewed in detail to discard false detections. We suggest that atmospheric parameters should not be used for these system components; SB-specific pipelines should be used instead. Conclusions: Our implementation of an automatic detection of spectroscopic binaries within the GES has allowed the efficient discovery of many new multiple systems. With the detection of the SB1 candidates that will be the subject of a forthcoming paper, the study of the statistical and physical properties of the spectroscopic multiple systems will soon be possible for the entire GES sample. Based on data products from observations made with ESO Telescopes at the La Silla Paranal Observatory under programme ID 188.B-3002. These data products have been processed by the Cambridge Astronomy Survey Unit (CASU) at the Institute of Astronomy, University of Cambridge, and by the FLAMES/UVES reduction team at INAF/Osservatorio Astrofisico di Arcetri. These data have been obtained from the Gaia-ESO Survey Data Archive, prepared and hosted by the Wide Field Astronomy Unit, Institute for Astronomy, University of Edinburgh, which is funded by the UK Science and Technology Facilities Council.

The Small Magellanic Cloud (SMC) hosts a large number of high-mass X-ray binaries, and in particular of Be/X-ray Binaries (BeXRBs; neutron stars orbiting OBe-type stars), offering a unique laboratory to address the effect of metalicity. One key property of their optical companion is Hα in emission, which makes them bright sources when observed through a narrow-band Hα filter. We performed a survey of the SMC Bar and Wing regions using wide-field cameras (WFI@MPG/ESO and MOSAIC@CTIO/Blanco) in order to identify the counterparts of the sources detected in our XMM-Newton survey of the same area. We obtained broad-band R and narrow-band Hα photometry, and identified ~10000 Hα emission sources down to a sensitivity limit of 18.7 mag (equivalent to ~B8 type Main Sequence stars). We find the fraction of OBe/OB stars to be 13% down to this limit, and by investigating this fraction as a function of the brightness of the stars we deduce that Hα excess peaks at the O9-B2 spectral range. Using the most up-to-date numbers of SMC BeXRBs we find their fraction over their parent population to be ~0.002 - 0.025 BeXRBs/OBe, a direct measurement of their formation rate.

X-ray surveys are believed to be the most efficient way to detect AGN. Recently though, optical variability studies are claimed to probe even fainter AGN. We are presenting results from an HST study aimed to identify Active Galactic Nuclei (AGN) through optical variability selection in the CDFS.. This work is part of the 'Hubble Catalogue of Variables'project of ESA that aims to identify variable sources in the Hubble Source Catalogue.' In particular, we used Hubble Space Telescope (HST) z-band images taken over 5 epochs and performed aperture photometry to derive the lightcurves of the sources. Two statistical methods (standard deviation & interquartile range) resulting in a final sample of 175 variable AGN candidates, having removed the artifacts by visual inspection and known stars and supernovae. The fact that the majority of the sources are extended and variable indicates AGN activity. We compare the efficiency of the method by comparing with the 7Ms Chandra detections. Our work shows that the optical variability probes AGN at comparable redshifts but at deeper optical magnitudes. Our candidate AGN (non detected in X-rays) have luminosities of L_x<6×10^{40} erg/sec at z∼0.7 suggesting that these are associated with low luminosity Seyferts and LINERS.

The XMM-Newton survey of M31 revealed extended diffuse emission in the northern disk of M31, which is well correlated with the star-forming ring of the galaxy. The stellar population of this part of M31 has been extensively studied in the optical in the Panchromatic Hubble Andromeda Treasury (PHAT) survey. We have observed the northern disk of M31 in areas within the PHAT footprint in deep XMM-Newton pointings. We have thus obtained a map of the X-ray emission of the hot interstellar medium (ISM) in a spiral galaxy like our own on arcmin scales and a complete list of X-ray sources down to the confusion limit of a few 10^{34} erg/s, with variability and spectral information for most of the sources. We will present the first results of the study of the X-ray source population and that of the hot ISM.

We aim to construct an exceptionally deep (V ≲ 27) catalog of variable objects in selected Galactic and extragalactic fields visited multiple times by the Hubble Space Telescope (HST). While HST observations of some of these fields were searched for specific types of variables before (most notably, the extragalactic Cepheids), we attempt a systematic study of the population of variable objects of all types at the magnitude range not easily accessible with ground-based telescopes. The variability timescales that can be probed range from hours to years depending on how often a particular field has been visited. For source extraction and cross-matching of sources between visits we rely on the Hubble Source Catalog which includes 107 objects detected with WFPC2, ACS, and WFC3 HST instruments. The lightcurves extracted from the HSC are corrected for systematic effects by applying local zero-point corrections and are screened for bad measurements. For each lightcurve we compute variability indices sensitive to a broad range of variability types. The indices characterize the overall lightcurve scatter and smoothness. Candidate variables are selected as having variability index values significantly higher than expected for objects of similar brightness in the given set of observations. The Hubble Catalog of Variables will be released in 2018.

Here we report the first set of new and recurrent X-ray transients found in two XMM-Newton 100-ks pointings of the M31 northern disk on Jan 1 and 21 (see ATel #8825).

We report the X-ray detections of three novae in observations of the M31 northern disk by XMM-Newton in January 2016. In continuation of earlier observations described in ATels #8227 and #8228, a further two 100-ks observations were carried out on 2016-01-01 (ObsID 0763120401) and 2016-01-21 (ObsID 0763120201).

Context. At about 1000 days after the launch of Gaia we present the first Gaia data release, Gaia DR1, consisting of astrometry and photometry for over 1 billion sources brighter than magnitude 20.7. Aims: A summary of Gaia DR1 is presented along with illustrations of the scientific quality of the data, followed by a discussion of the limitations due to the preliminary nature of this release. Methods: The raw data collected by Gaia during the first 14 months of the mission have been processed by the Gaia Data Processing and Analysis Consortium (DPAC) and turned into an astrometric and photometric catalogue. Results: Gaia DR1 consists of three components: a primary astrometric data set which contains the positions, parallaxes, and mean proper motions for about 2 million of the brightest stars in common with the Hipparcos and Tycho-2 catalogues - a realisation of the Tycho-Gaia Astrometric Solution (TGAS) - and a secondary astrometric data set containing the positions for an additional 1.1 billion sources. The second component is the photometric data set, consisting of mean G-band magnitudes for all sources. The G-band light curves and the characteristics of 3000 Cepheid and RR Lyrae stars, observed at high cadence around the south ecliptic pole, form the third component. For the primary astrometric data set the typical uncertainty is about 0.3 mas for the positions and parallaxes, and about 1 mas yr-1 for the proper motions. A systematic component of 0.3 mas should be added to the parallax uncertainties. For the subset of 94 000 Hipparcos stars in the primary data set, the proper motions are much more precise at about 0.06 mas yr-1. For the secondary astrometric data set, the typical uncertainty of the positions is 10 mas. The median uncertainties on the mean G-band magnitudes range from the mmag level to 0.03 mag over the magnitude range 5 to 20.7. Conclusions: Gaia DR1 is an important milestone ahead of the next Gaia data release, which will feature five-parameter astrometry for all sources. Extensive validation shows that Gaia DR1 represents a major advance in the mapping of the heavens and the availability of basic stellar data that underpin observational astrophysics. Nevertheless, the very preliminary nature of this first Gaia data release does lead to a number of important limitations to the data quality which should be carefully considered before drawing conclusions from the data.

Gaia is a cornerstone mission in the science programme of the EuropeanSpace Agency (ESA). The spacecraft construction was approved in 2006, following a study in which the original interferometric concept was changed to a direct-imaging approach. Both the spacecraft and the payload were built by European industry. The involvement of the scientific community focusses on data processing for which the international Gaia Data Processing and Analysis Consortium (DPAC) was selected in 2007. Gaia was launched on 19 December 2013 and arrived at its operating point, the second Lagrange point of the Sun-Earth-Moon system, a few weeks later. The commissioning of the spacecraft and payload was completed on 19 July 2014. The nominal five-year mission started with four weeks of special, ecliptic-pole scanning and subsequently transferred into full-sky scanning mode. We recall the scientific goals of Gaia and give a description of the as-built spacecraft that is currently (mid-2016) being operated to achieve these goals. We pay special attention to the payload module, the performance of which is closely related to the scientific performance of the mission. We provide a summary of the commissioning activities and findings, followed by a description of the routine operational mode. We summarise scientific performance estimates on the basis of in-orbit operations. Several intermediate Gaia data releases are planned and the data can be retrieved from the Gaia Archive, which is available through the Gaia home page. http://www.cosmos.esa.int/gaia

Here we report the second set of new and recurrent X-ray transients found in two XMM-Newton 100-ks pointings of the M31 northern disk on Jan 1 and 21 (see ATels #8825, #8826).

We report the detection of three new X-ray transients and one recurrent X-ray source in recent XMM-Newton observations of the M31 disk. Two 100-ks observations were carried out on 2015-06-28 (ObsID 0763120101; June) and 2015-08-11 (ObsID 0763120301; August).

We report the detection of three novae in recent XMM-Newton observations of the M31 disk (see also ATel #8227). Two 100-ks observations were carried out on 2015-06-28 (ObsID 0763120101; June) and 2015-08-11 (ObsID 0763120301; August) and have been analysed using the standard data reduction software.

Novae are the major class of supersoft X-ray sources (SSSs) in the central region of our neighbouring galaxy Andromeda (M31). From 2006 until 2012 we carried out a dedicated monitoring of the M31 central region with XMM-Newton and Chandra that was specifically designed to detect and characterise SSS states of novae. Only X-ray observations allow us to observe the hot post-nova white dwarf directly and study its physics. Here, I present new results based on an updated catalogue of 79 novae with SSS counterparts, which is by far the largest sample known in any galaxy, to date. Global trends and correlations were established between various multiwavelength nova parameters and there appear to be significant deviations from current models of Galactic novae. Furthermore, there is evidence for different X-ray parameters of sub-samples associated with the M31 bulge and disk, although the question whether both populations are inherently different is far from resolved. The sample contains several remarkable individual novae and I will discuss their peculiarities and importance. The X-ray monitoring of large, homogeneous samples of extragalactic novae is shown to be a powerful tool to study nova populations and the dependence of their observable characteristics on the underlying stellar population.

The Small Magellanic Cloud (SMC) is well known to harbour a large number of high-mass X-ray binaries (HMXBs). The identification of their optical counterparts provides information on the nature of the donor stars and can help to constrain the parameters of these systems and their evolution. We obtained optical spectra for a number of HMXBs identified in previous Chandra and XMM-Newton surveys of the SMC using the AAOmega/2dF fibre-fed spectrograph at the Anglo-Australian Telescope. We find five new Be/X-ray binaries (BeXRBs; including a tentative one), by identifying the spectral type of their optical counterparts, and we confirm the spectral classification of an additional 15 known BeXRBs. We compared the spectral types, orbital periods and eccentricities of the BeXRB populations in the SMC and the Milky Way and we find marginal evidence for difference between the spectral type distributions, but no statistically significant differences for the orbital periods and the eccentricities. Moreover, our search revealed that the well-known supergiant B[e] star LHA 115-S 18 (or AzV 154) is associated with the weak X-ray source CXOU J005409.57-724143.5. We provide evidence that the supergiant star LHA 115-S 18 is the optical counterpart of the X-ray source, and we discuss different possibilities of the origin of its low X-ray luminosity (Lx ∼ 4 × 1033 erg s-1).

Context. Classical novae (CNe) represent the major class of supersoft X-ray sources (SSSs) in the central region of our neighbouring galaxy M 31. Aims: We performed a dedicated monitoring of the M 31 central region, which aimed to detect SSS counterparts of CNe, with XMM-Newton and Chandra between Nov. and Mar. of the years 2009/10, 2010/11, and 2011/12. Methods: We systematically searched our data for X-ray counterparts of CNe and determined their X-ray light curves and also their spectral properties in the case of XMM-Newton data. Additionally, we determined luminosity upper limits for all previously known X-ray emitting novae, which are not detected anymore, and for all CNe in our field of view with recent optical outbursts. Results: In total, we detected 24 novae in X-rays. Seven of these sources were known from previous observations, including the M 31 nova with the longest SSS phase, M31N 1996-08b, which was found to fade below our X-ray detection limit 13.8 yr after outburst. Of the new discoveries, several novae exhibit significant variability in their short-term X-ray light curves with one object showing a suspected period of about 1.3 h. We studied the SSS state of the most recent outburst of a recurrent nova, which had previously shown the shortest time ever observed between two outbursts (~5 yr). The total number of M 31 novae with X-ray counterpart was increased to 79, and we subjected this extended catalogue to detailed statistical studies. Four previously indicated correlations between optical and X-ray parameters could be confirmed and improved. Furthermore, we found indications that the multi-dimensional parameter space of nova properties might be dominated by a single physical parameter, and we provide interpretations and suggest implications. We studied various outliers from the established correlations and discuss evidence of a different X-ray behaviour of novae in the M 31 bulge and disk. Conclusions: Exploration of the multi-wavelength parameter space of optical and X-ray measurements is shown to be a powerful tool for examining properties of extragalactic nova populations. While there are hints that the different stellar populations of M 31 (bulge vs. disk) produce dissimilar nova outbursts, there is also growing evidence that the overall behaviour of an average nova might be understood in surprisingly simple terms. Partly based on observations with XMM-Newton, an ESA Science Mission with instruments and contributions directly funded by ESA Member States and NASA.Tables 1-9 are only available at the CDS via anonymous ftp to http://cdsarc.u-strasbg.fr (ftp://130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/563/A2

This work is based on XMM-Newton and Chandra observations 30.0 of the central area of M 31 that were dedicated to the monitoring of SSS states of novae (PI: W. Pietsch). We report on the analysis of three observation campaigns carried out during Nov 2009 to Feb 2010, Nov 2010 to Mar 2011, and Nov 2011 to Mar 2012. (10 data files).

We report the detection of two M 31 novae as supersoft X-ray sources (SSS) in a recent XMM-Newton target of opportunity (ToO) observation. The 24 ks observation was obtained on 2014-08-09.89 UT to study the SSS emission of nova M31N 2014-02a, previously detected by Swift (ATel #6374).

Context. Chemically inhomogeneous populations are observed in most globular clusters, but not in open clusters. Cluster mass seems to play a key role in the existence of multiple populations. Aims: Studying the chemical homogeneity of the most massive open clusters is needed to better understand the mechanism of their formation and determine the mass limit under which clusters cannot host multiple populations. Here we studied NGC 6705, which is a young and massive open cluster located towards the inner region of the Milky Way. This cluster is located inside the solar circle. This makes it an important tracer of the inner disk abundance gradient. Methods: This study makes use of BVI and ri photometry and comparisons with theoretical isochrones to derive the age of NGC 6705. We study the density profile of the cluster and the mass function to infer the cluster mass. Based on abundances of the chemical elements distributed in the first internal data release of the Gaia-ESO Survey, we study elemental ratios and the chemical homogeneity of the red clump stars. Radial velocities enable us to study the rotation and internal kinematics of the cluster. Results: The estimated ages range from 250 to 316 Myr, depending on the adopted stellar model. Luminosity profiles and mass functions show strong signs of mass segregation. We derive the mass of the cluster from its luminosity function and from the kinematics, finding values between 3700 M⊙ and 11 000 M⊙. After selecting the cluster members from their radial velocities, we obtain a metallicity of [Fe/H] = 0.10 ± 0.06 based on 21 candidate members. Moreover, NGC 6705 shows no sign of the typical correlations or anti-correlations between Al, Mg, Si, and Na, which are expected in multiple populations. This is consistent with our cluster mass estimate, which is lower than the required mass limit proposed in the literature to develop multiple populations. Based on the data obtained at ESO telescopes under programme 188.B-3002 (the public Gaia-ESO spectroscopic survey, PIs Gilmore and Randich) and on the archive data of the programme 083.D-0671.Full Table 2 is only available at the CDS via anonymous ftp to http://cdsarc.u-strasbg.fr (ftp://130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/569/A17

We present new optical spectroscopy of 20 candidate counterparts of 17 X-ray sources in the direction of the M31 disc. By comparing the X-ray catalogue from the XMM-Newton survey of M31 with star catalogues from the Local Group Galaxy Survey, we chose counterpart candidates based on optical colour and X-ray hardness. We have discovered 17 counterpart candidates with spectra containing stellar features. Eight of these are early-type stars of O or B type in M31, with hard X-ray spectra, making them good high-mass X-ray binary (HMXB) candidates. Three of these eight exhibit emission lines, which we consider to be the strongest HMXB candidates. In addition, our spectra reveal two likely Galactic cataclysmic variables, one foreground M star, two probable low-mass X-ray binaries related to M31 globular clusters, one emission-line region with an embedded Wolf-Rayet star and one newly discovered supernova remnant. Finally, two of the sources have stellar spectra with no features indicative of association with an X-ray source.

We combine new BV photometry with the spectroscopic observations of the Gaia-ESO Survey to study the open cluster NGC6 705. 1028 stars were observed with the HR15n grating of the GIRAFFE instrument at VLT/UT2. The radial velocities obtained for those stars were used to derive membership probabilities. (1 data file).

The XMM-Newton survey of the Small Magellanic Cloud (SMC) yields a complete coverage of the bar and eastern wing in the 0.2-12.0keV band. This catalogue comprises 3053 unique X-ray point sources and sources with moderate extent that have been reduced from 5236 individual detections found in observations between April 2000 and April 2010. Sources have a median position uncertainty of 1.3" (1σ) and limiting fluxes down to ~1*10-14erg/s/cm2 in the 0.2-4.5keV band, corresponding to 5*1033erg/s for sources in the SMC. Sources have been classified using hardness ratios, X-ray variability, and their multi-wavelength properties. In addition to the main-field (5.58deg2) available outer fields have been included in the catalogue, yielding a total field area of 6.32deg2. X-ray sources with high extent (>40", e.g. supernova remnants and galaxy cluster) have been presented by Haberl et al. (2012, Cat. J/A+A/545/A128) (2 data files).

Context. The central field of the Andromeda galaxy (M 31) was monitored from 2006 to 2012 using the Chandra HRC-I detector (about 0.1-10 keV energy range) with the main aim of detecting X-rays from optical novae. We present a systematic analysis of all X-ray sources found in the 41 nova monitoring observations, along with 23 M 31 central field HRC-I observations available from the Chandra data archive starting in December 1999. Aims: Based on these observations, we studied the X-ray long-term variability of the source population and especially of X-ray binaries in M 31. Methods: We created a catalogue of sources detected in the 64 available observations that adds up to a total exposure time of about 1 Ms. To study the variability, we developed a processing pipeline to derive long-term Chandra HRC-I light curves for each source over the 13 years of observations. We also searched for extended X-ray sources in the merged images. Results: We present a point-source catalogue containing 318 X-ray sources with detailed long-term variability information, 28 of which are published for the first time. The spatial and temporal resolution of the catalogue allows us to classify 115 X-ray binary candidates showing high X-ray variability or even outbursts, as well as 14 globular cluster X-ray binary candidates showing no significant variability. The analysis may suggest that outburst sources are less frequent in globular clusters than in the field of M 31. We detected seven supernova remnants, one of which is a new candidate, and also resolved the first X-rays from a known radio supernova remnant. In addition to 33 known optical nova/X-ray source correlations, we discovered one previously unknown super-soft X-ray outburst and several new nova candidates. Conclusions: The catalogue contains a large sample of detailed long-term X-ray light curves in the M 31 central field, which helps in understanding the X-ray population of our neighbouring spiral galaxy M 31. Tables 1 and 2 are only available at the CDS via anonymous ftp to http://cdsarc.u-strasbg.fr (ftp://130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/555/A65

The Small Magellanic Cloud (SMC) is a well known laboratory for studies of High-Mass X-ray Binaries (HMXBs), that are prime targets to investigate the evolution of binaries and massive stars. Although the number of identified Be X-ray Binaries (BeXRBs) has increased dramatically in the last decade, only recently we started to obtain a better picture of their their spectral-type distributions, which in turn can provide us with information and constrains regarding their evolution and nature. We present results from a systematic spectroscopic campaign of HMXBs identified in Chandra and XMM-Newton surveys of the SMC, using the AAOmega/2dF spectrograph at the the Anglo-Australian Telescope. We classified 21 sources, one of which is the well known supergiant B[e] star S18 (or AzV 154). We suggest that it is the optical counterpart of the X-ray source CXOU J005409.57-724143.5, being the second supergiant X-ray binary in the SMC since 1971. The classified sources are within a wide range of five orders of X-ray luminosity, extending our census of BeXRBs to almost quiescent luminosities. A comparison of the populations of HMXBs in the SMC and the Milky Way with respect to their spectral types and orbital parameters (periods and eccentricities) shows no evidence for difference in their populations. In order to expand the sample of HMXBs we performed a systematic survey on selected active regions of the SMC. Since the optical counterparts of the HMXBs display Hα excess they can be identified through Hα imaging. Thus, we observed 16 regions with the Wide Field Imager at MPG/ESO and the MOSAIC II Imager at CTIO Blanco telescopes. The analysis of these data yields approximately 3000 identified Hα emitting stars in the most active regions of the SMC. We discuss the photometric parameters of these sources (Hα EW, broad-band optical and IR colors), and their correlation with the X-ray sources identified in the Chandra and XMM-Newton surveys.

For all Chandra HRC-I observations a source catalogue was created and the energy flux of each source in each observation was derived. Fluxes were calculated assuming a generic power law spectrum and Galactic foreground absorption for each source. (5 data files).

The present study is based on observations obtained with the 1.3m Warsaw telescope at the Las Campanas Observatory, Chile, during phase III of the OGLE project, between 2001 and 2009 (Soszynski et al., 2010, cat. J/AcA/60/165) (3 data files).

A subset of ultraluminous X-ray sources (those with luminosities of less than 1040 erg s-1 ref. 1) are thought to be powered by the accretion of gas onto black holes with masses of ~5-20, probably by means of an accretion disk. The X-ray and radio emission are coupled in such Galactic sources; the radio emission originates in a relativistic jet thought to be launched from the innermost regions near the black hole, with the most powerful emission occurring when the rate of infalling matter approaches a theoretical maximum (the Eddington limit). Only four such maximal sources are known in the Milky Way, and the absorption of soft X-rays in the interstellar medium hinders the determination of the causal sequence of events that leads to the ejection of the jet. Here we report radio and X-ray observations of a bright new X-ray source in the nearby galaxy M 31, whose peak luminosity exceeded 1039 erg s-1. The radio luminosity is extremely high and shows variability on a timescale of tens of minutes, arguing that the source is highly compact and powered by accretion close to the Eddington limit onto a black hole of stellar mass. Continued radio and X-ray monitoring of such sources should reveal the causal relationship between the accretion flow and the powerful jet emission.

We review the first results of a dedicated, on-going monitoring project for supersoft X-ray source (SSS) states of classical novae (CNe) in the central region of the Andromeda galaxy (M 31). So far, during three high-cadence observation campaigns with the X-ray telescopes XMM-Newton and Chandra from 2006 until 2009 we detected 21 CNe, only four of which were seen in X-rays before. This increased the total number of known CNe with X-ray counterparts in M 31 to 60, which is significantly larger than for any other galaxy, including the Milky Way. We compiled a catalog of X-ray and optical properties for these 60 sources which allowed us to perform source statistics and population studies of CNe with SSS state in M 31 for the first time. Here we review the results of this analysis: (i) several correlations between X-ray and optical parameters, (ii) an analysis of the intrinsic fraction of CNe with SSS state, and (iii) the first nova population study in X-rays. Our first results are promising, however a continuing monitoring of the unique target M 31 is strongly needed to extend this valuable data base and to refine the early statements and predictions.

Context. Classical novae (CNe) represent the main class of supersoft X-ray sources (SSSs) in the central region of our neighbouring galaxy M 31. Only three confirmed novae and three SSSs have been discovered in globular clusters (GCs) of any galaxy so far, of which one nova and two SSSs (including the nova) were found in M 31 GCs. Aims: To study the SSS state of CNe we carried out a high-cadence X-ray monitoring of the M 31 central area with XMM-Newton and Chandra. This project is supplemented by regular optical monitoring programmes at various observatories. Methods: We analysed X-ray and optical monitoring data of a new transient X-ray source in the M 31 GC Bol 126, discovered serendipitously in Swift observations. Our optical data set was based on regular M 31 monitoring programmes from five different small telescopes and was reduced using a homogeneous method. Additionally, we made use of Pan-STARRS 1 data obtained during the PAndromeda survey. We extracted light curves of the source in the optical and X-rays, as well as X-ray spectra. Results: Our observations reveal that the X-ray source in Bol 126 is the third SSS in an M 31 GC and can be confirmed as the second CN in the M 31 GC system. This nova is named M31N 2010-10f. Its properties in the X-ray (high black-body temperature, short SSS phase) and optical (relatively high maximum magnitude, fast decline) regimes agree with a massive white dwarf (MWD ≳ 1.3 M⊙) in the binary system. Incorporating the data on previously found (suspected) novae in M 31 GCs we used our high-cadence X-ray monitoring observations to estimate a tentative nova rate in the M 31 GC system of 0.05 yr-1 GC-1. An optical estimate, based on the recent 10.5-year WeCAPP survey, gives a lower nova rate, which is compatible with the X-ray rate on the 95% confidence level. Conclusions: Although still based on small-number statistics, there is growing evidence that the nova rate in GCs is higher than expected from primordial binary formation and under conditions as in the field. Dynamical binary formation and/or additional accretion from the intracluster medium are possible scenarios for an increased nova rate, but observational confirmation for this enhancement has been absent, so far. Regular X-ray monitoring observations of M 31 provide a promising strategy to find these novae. Partly based on observations with XMM-Newton, an ESA Science Mission with instruments and contributions directly funded by ESA Member States and NASA.Tables 1-3 are available in electronic form at http://www.aanda.org

Context. Local-Group galaxies provide access to samples of X-ray source populations of whole galaxies. The XMM-Newton survey of the Small Magellanic Cloud (SMC) completely covers the bar and eastern wing with a 5.6 deg2 area in the (0.2-12.0) keV band. Aims: To characterise the X-ray sources in the SMC field, we created a catalogue of point sources and sources with moderate extent. Sources with high extent (≥40'') have been presented in a companion paper. Methods: We searched for point sources in the EPIC images using sliding-box and maximum-likelihood techniques and classified the sources using hardness ratios, X-ray variability, and their multi-wavelength properties. Results: The catalogue comprises 3053 unique X-ray sources with a median position uncertainty of 1.3'' down to a flux limit for point sources of ~10-14 erg cm-2 s-1 in the (0.2-4.5) keV band, corresponding to 5 × 1033 erg s-1 for sources in the SMC. We discuss statistical properties, like the spatial distribution, X-ray colour diagrams, luminosity functions, and time variability. We identified 49 SMC high-mass X-ray binaries (HMXB), four super-soft X-ray sources (SSS), 34 foreground stars, and 72 active galactic nuclei (AGN) behind the SMC. In addition, we found candidates for SMC HMXBs (45) and faint SSSs (8) as well as AGN (2092) and galaxy clusters (13). Conclusions: We present the most up-to-date catalogue of the X-ray source population in the SMC field. In particular, the known population of X-ray binaries is greatly increased. We find that the bright-end slope of the luminosity function of Be/X-ray binaries significantly deviates from the expected universal high-mass X-ray binary luminosity function. Based on observations obtained with XMM-Newton an ESA science mission with instruments and contributions directly funded by ESA Member States and NASACatalogue is only available at the CDS via anonymous ftp to http://cdsarc.u-strasbg.fr (ftp://130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/558/A3

In contrast to the Small Magellanic Cloud (SMC), the Large Magellanic Cloud (LMC), our nearest starforming galaxy with metallicity between the Galaxy and the SMC, has received little attention in X-rays so far. With the aim to compare the accreting X-ray binary (XRB) populations in two of our nearest star-forming galaxies, we recently compiled the most complete census of high-mass X-ray binaries (HMXBs) in the LMC. We found 43 members of which 13 are XRB pulsars, while we also identified their most likely optical counterpart (previously, half of these sources lacked an identification). Using this census, we investigated the link between the young accreting XRBs and their parent stellar populations. It was known that HMXBs can be used as star-formation (SF) rate indicators, but these first studies have been focused only on bright systems (Galaxy: >1038 erg s-1, Magellanic Clouds: >1036 erg s-1) and SF values for the whole galaxy. By including Magellanic Cloud sources with X-ray luminosities at least two order of magnitudes fainter than the above limits and by utilizing the detailed, spatially resolved, SF history maps of these galaxies, we were able to provide observational constraints on ill-understood parameters related to their formation and evolution (such as the kick velocities imparted into the neutron star during the supernova explosion) and to derive their formation efficiency. This work was mainly supported by the National Aeronautics and Space Administration under Grant No. NNX10AH47G issued through the Astrophysics Data Analysis Program.

The Small Magellanic Cloud (SMC) is host to approximately 100 High-Mass X-ray Binaries (HMXBs), predominantly Be X-ray Binaries (BeXRBs), a number which is surprisingly high when compared to the Milky Way. As these galaxies present different metallicities it is reasonable to ask if their populations of HMXBs are different. In order to address this we investigated their properties such as their spectral types and orbital parameters (periods and eccentricities). We find no apparent differences, implying that the nature of these systems is similar which sets at the same time strong constraints on the magnitude of supernova kicks in low metallicities. In order to extend the sample of BeXRBs we performed a systematic photometric survey of selected active regions of the SMC. Since the optical counterparts of the BeXRBs display Halpha excess they can be identified through Halpha imaging. Observations in 5 regions with the Wide Field Imager at the 2.2m MPG/ESO telescope yield approximately 24000 Halpha emitting stars. By cross-correlating these sources with those identified in the Chandra and XMM-Newton shallow surveys of the SMC and the census of HMXBs of Liu et al. (2005), we find 34 Halpha emitting X-ray sources. These are most likely BeXRBs, which we will confirm with follow-up spectroscopic runs.

We use JHK photometry from the 2MASS catalog to construct color-magnitude diagrams and density profiles of intermediate age open clusters in the Galaxy, that appear to contain carbon stars within their radius. The clusters in the sample have not been extensively studied in the past, as they are often very low density as well as extended and therefore difficult to observe. We have used the most recent Padova isochrones (Bressan et al. 2013) to estimate the ages of the clusters.

We present radial profiles and color magnitude diagrams for 18 star clusters in the central region of the neighboring irregular galaxy Small Magellanic Cloud (SMC), using BVR photometric data obtained with the Inamori Magellan Areal Camera and Spectrograph (IMACS) mounted on the 6.5m Magellan Telescope at the Las Campanas Observatory in Chile. The star clusters studied (OEi79, NGC330, H86- 135, H86-129, H86-127, H86-138, NGC306, H86-146, SOGLE220, B69 OE- SOGLE89, H86-136, H86- 145, BS259, H86-149, H86-142, H86-119, BS257, B73 or SOGLE96) are distributed over a 0.44o field centered at RA: 00h 53m 28.2s, DEC:-72o26?Ao34.5?Ao?Ao (2000) in the central bar and have been previously catalogued by Bonnato & Bica (2010), Glatt et al. (2010) and Chiosi et al. (2006). The observations obtained with IMACS have very high spatial resolution (of about 0.2 arcsec) and they are thus very well suited for studies of crowded fields. Some of the objects that had been previously classified as clusters in the aforementioned catalogues, have not been confirmed as such, by the new high resolution data. It is also noteworthy that only one of the 18 star clusters has been observed with the Hubble Space Telescope ?Ai and thus with high spatial resolution. For all of the confirmed star clusters in the sample, we have constructed radial density profiles, color magnitude and color-color diagrams. Ages were estimated using the Padova isochrones of Bressan et al. (2012), while the interstellar reddening of each cluster was estimated both from the location of the zero-age main sequence and from the color-color diagrams.

This study is based on observations obtained with the 1.3-m Warsaw telescope at the Las Campanas Observatory, Chile, during the OGLE-II and OGLE-III projects, between 1997 and 2008. (4 data files).

M31 is our nearest spiral galaxy, at a distance of 780 kpc. Identification of X-ray sources in nearby galaxies is important for interpreting the properties of more distant ones, mainly because we can classify nearby sources using both X-ray and optical data, while more distant ones via X-rays alone. The XMM-Newton Large Project for M31 has produced an abundant sample of about 1900 X-ray sources in the direction of M31. Most of them remain elusive, giving us little signs of their origin. Our goal is to classify these sources using criteria based on properties of already identified ones. In particular we construct candidate lists of high mass X-ray binaries, low mass X-ray binaries, X-ray binaries correlated with globular clusters and AGN based on their X-ray emission and the properties of their optical counterparts, if any. Our main methodology consists of identifying particular loci of X-ray sources on X-ray hardness ratio diagrams and the color magnitude diagrams of their optical counterparts. Finally, we examined the X-ray luminosity function of the X-ray binaries populations.

In this work, we study the properties of the overall accreting binary population of the Magellanic Clouds and the connection between star-formation (SF) activity and X-ray binary (XRB) formation and evolution. Understanding of the populations of compact objects and their connection with SF will allow us to investigate channels of XRB formation in a variety of environments and therefore help in studies of the X-ray source populations of star-forming galaxies outside our Local Group, and even enable their use as a SF diagnostic. By using surveys carried out with space-based X-ray and infrared observatories and ground-based telescopes, we address the demographics of the most common type of young XRBs in the two nearest star-forming galaxies. Our program makes use of multiwavelength data sets in order to provide better understanding of the physical parameters which influence the XRB formation rate and evolution, such as the metallicity and the age of the parent stellar populations. In the SMC, the dominant Be-XRB population appears to be linked to the increased SF activity at ~25-60 Myr ago, while in the Large Magellanic Cloud this activity is shifted to earlier ages (at only ~10-50 Myr). The similarity of this age with the age of maximum occurrence of the Be phenomenon (~40 Myr) indicates that the presence of a circumstellar decretion disk plays a significant role in the number of observed XRBs in the 10-100 Myr age range.

We review recent results of the first dedicated monitoring programme for supersoft X-ray source (SSS) states of classical novae (CNe) in the central region of the Andromeda galaxy ({M 31}), performed in high-cadence campaigns with {XMM-Newton } and Chandra. After the first three years we had detected 21 novae in X-rays (17 new), thereby discovering peculiar objects and increasing the number of known {M 31} novae with SSS state to 60. This is the largest sample known in any galaxy and we used it to carry out the first statistical analysis of novae in X-rays. We found several correlations between optical and SSS parameters, and carried out a simulation on the completeness of our monitoring as well as the first nova population study in X-rays. This shows that X-ray surveys of CNe populations are a powerful tool to address the open questions connected to these objects.

We have performed the Fourier decomposition analysis of 8- and 13-yr V-band light curves of a carefully selected sample of 454 fundamental-mode RR Lyrae variables (RRab type), detected in an ≃14 square degree area of the Small Magellanic Cloud (SMC) and listed in the Optical Gravitational Lensing Experiment, phase III, Catalogue of Variable Stars. The Fourier decomposition parameters were used to derive metal abundances and distance moduli, following the methodology described by Kapakos, Hatzidimitriou & Soszyński. The average metal abundance of the RRab stars on the new scale of Carretta et al. was found to be <[Fe/H]C09> = -1.69 ± 0.41 dex (std, with a standard error of 0.02 dex). A tentative metallicity gradient of -0.013 ± 0.007 dex kpc-1 was detected, with increasing metal abundance towards the dynamical centre of the SMC, but selection effects are also discussed. The distance modulus of the SMC was re-estimated and was found to be <μ> = 19.13 ± 0.19 (std) in a distance scale where the distance modulus of the Large Magellanic Cloud (LMC) is μLMC = 18.52 ± 0.06 (std). The average 1σ line-of-sight depth was found to be σ int =5.3±0.4 kpc (std), while spatial variations of the depth were detected. The SMC was found to be deeper in the north-eastern region, while metal-richer and metal-poorer objects in the sample seem to belong to different dynamical structures. The former have smaller scale height and may constitute a thick disc, its width being 10.40 ± 0.02 kpc, and a bulge whose size (radius) is estimated to be 2.09 ± 0.81 kpc. The latter seem to belong to a halo structure with a maximum depth along the line of sight extending over 16 kpc in the SMC central region and falling to ∼12 kpc in the outer regions.

Context. Although numerous archival XMM-Newton observations existed towards the Small Magellanic Cloud (SMC) before 2009, only a fraction of the whole galaxy had been covered. Aims: Between May 2009 and March 2010, we carried out an XMM-Newton survey of the SMC, to ensure a complete coverage of both its bar and wing. Thirty-three observations of 30 different fields with a total exposure of about one Ms filled the previously missing parts. Methods: We systematically processed all available SMC data from the European Photon Imaging Camera. After rejecting observations with very high background, we included 53 archival and the 33 survey observations. We produced images in five different energy bands. We applied astrometric boresight corrections using secure identifications of X-ray sources and combined all the images to produce a mosaic covering the main body of the SMC. Results: We present an overview of the XMM-Newton observations, describe their analysis, and summarise our first results, which will be presented in detail in follow-up papers. Here, we mainly focus on extended X-ray sources, such as supernova remnants (SNRs) and clusters of galaxies, that are seen in our X-ray images. Conclusions: Our XMM-Newton survey represents the deepest complete survey of the SMC in the 0.15 - 12.0 keV X-ray band. We propose three new SNRs that have low surface brightnesses of a few 10-14 erg cm-2 s-1 arcmin-2 and large extents. In addition, several known remnants appear larger than previously measured at either X-rays or other wavelengths extending the size distribution of SMC SNRs to larger values. Based on observations with XMM-Newton, an ESA Science Mission with instruments and contributions directly funded by ESA Member states and the USA (NASA).Table 1 is available in electronic form at http://www.aanda.orgFITS images are only available at the CDS via anonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/545/A128

We request multi-fiber optical spectroscopic observations (using the AAOmega/2dF spectrograph at AAT) of the central region of the Small Magellanic Cloud, in order to determine the donor type of the identified X-ray binaries (XRBs) detected in our large XMM survey of the same area. This way we will unambiguously classify the XRBs into Be (easily identifiable by their Hα emission) or supergiant systems. These observations will create a complete census of early-type line-emitting SMC stars down to V~19 mag, thus allowing to address: i) the fraction of early-type stars that exhibit Hα emission and the connection between their Hα excess and red excess or brightness, ii) the fraction of such sources that are observed in X-rays, which is important for constraining the formation rate of accreting binaries in an environment with well characterized stellar populations, and iii) the spectral-type distribution of low-luminosity XRBs.

Recently Varvoglis and Hadjidemetriou (Astrophys. Space Sci. doi:10.1007/s10509-012-1060-3, 2012; hereafter referred to as paper VH) have raised two points concerning the model of the restricted three-body problem with variable mass presented in our paper (Zhang et al. in Astrophys. Space Sci. 337:107, 2012; hereafter referred to as paper ZZX) and made intensive investigations of this model. These points and investigations are very useful and here we provide some explanation and supplementary specification regarding the model presented in the paper ZZX.

Context. We present the analysis of supernova remnants (SNRs) and candidates in M 31 identified in the XMM-Newton large programme survey of M 31. Supernova remnants are among the brightest X-ray sources in a galaxy. They are good indicators of the recent star-formation activities of galaxies and the interstellar environment in which they evolve. Aims: By combining the X-ray data of sources in M 31 with optical data as well as optical and radio catalogues, we aim to compile a complete, revised list of SNRs emitting X-rays in M 31 detected with XMM-Newton, study their luminosity and spatial distributions, and understand the X-ray spectra of the brightest SNRs. Methods: We analysed the X-ray spectra of the 12 brightest SNRs and candidates that have been observed with XMM-Newton. Our study of the four brightest sources allowed us to perform a more detailed spectral analysis and compare different models to describe their spectrum. For all M 31 large programme sources, we searched for their optical counterparts in the Hα, [S ii], and [O iii] images of the Local Group Galaxy Survey. Results: We confirm 21 X-ray sources as counterparts to known SNRs. In addition, we identify 5 new X-ray sources as X-ray and optically emitting SNRs. Seventeen sources are no longer considered as SNR candidates. We thus create a list of 26 X-ray SNRs and 20 X-ray SNR candidates in M 31 based on their X-ray, optical, and radio emission, which is the most recent complete list of X-ray SNRs in M 31. The brightest SNRs have X-ray luminosities of up to 8 × 1036 erg s-1 in the 0.35-2.0 keV band. Based on observations obtained with XMM-Newton, an ESA science mission with instruments and contributions directly funded by ESA Member States and NASA.Appendices are available in electronic form at http://www.aanda.org

X-ray mosaic images from combined EPIC pn and MOS data of the SMC region centred at RA=01:00:30, DE=-72:28:00 (J2000). The three images were produced in the three energy bands 0.2-1.0keV, 1.0-2.0keV, and 2.0-4.5keV. The images are exposure-corrected and for EPIC pn out-of-time event subtracted, but not detector-background subtracted and not vignetting-corrected. (4 data files).

In the course of the XMM-Newton survey of the Small Magellanic Cloud (SMC), two new bright X-ray sources were discovered exhibiting the spectral characteristics of high-mass X-ray binaries - but revealing only weak evidence for pulsations in just one of the objects (at 153 s in XMMU J010743.1-715953). The accurate X-ray source locations permit the identification of these X-ray sources with Be stars, thereby strongly suggesting that these systems are new Be/X-ray binaries. From blue spectra the proposed classification for XMMU J010633.1-731543 is B0.5-1Ve and for XMMU J010743.1-715953 it is B2IV-Ve.

Research on star clusters and associations includes the observation and theory of stellar groupings as they form and evolve, cluster disruption, stellar interactions inside clusters, and star formation in dense environments. In what follows, we list past, present and future meetings (http://www2.cadc-ccda.hia-iha.nrc-cnrc.gc.ca/meetings/), publications statistics and important surveys, reviews, and databases about clusters.

Division VII provides a forum for astronomers studying the Milky Way as a galactic system, as well as its constituents. It acts as an umbrella for two commissions, Commission 33 and Commission 37.

The Gaia-ESO Public Spectroscopic Survey has begun and will obtain high quality spectroscopy of some 100000 Milky Way stars, in the field and in open clusters, down to magnitude 19, systematically covering all the major components of the Milky Way. This survey will provide the first homogeneous overview of the distributions of kinematics and chemical element abundances in the Galaxy. The motivation, organisation and implementation of the Gaia-ESO Survey are described, emphasising the complementarity with the ESA Gaia mission. Spectra from the very first observing run of the survey are presented.

We found that the nova candidate J004457.9+412344 is a radio-quiet quasar at z ∼ 2. Its optical long-term light curve, covering more than half a century, shows quasar typical flux variations superimposed by a spectacular single flare lasting more than one year (observer frame). We could not find comparable light curves among the several thousand catalogued radio-quiet quasars in the stripe 82 of the Sloan Digital Sky Survey. The decreasing part of the flare light curve roughly follows a power law t-5/3. The quasar spectrum, the total energy of the flare, and the decline of the light curve are consistent with the tidal disruption of a ∼10 Mʘ giant star by a supermassive black hole of a few 108 Mʘ. We argue that the alternative explanation by gravitational microlensing is less likely, though it cannot be definitely excluded.

We have performed the Fourier decomposition analysis of 11-yr V-band light curves of a carefully selected sample of 100 RR Lyrae variables, detected in the central regions of the Small Magellanic Cloud (SMC), with the Optical Gravitational Lensing Experiment, phases II and III. The sample consisted of 84 fundamental mode pulsators (RRab stars) and 16 first-overtone pulsators (RRc stars). The Fourier decomposition parameters were used to derive metal abundances and distance moduli for these RR Lyrae variables. The average metal abundance of the RRab stars on the new scale of Carretta et al. is found to be <[Fe/H]C09>=-1.62 ± 0.41 dex (std, with a standard error of 0.05 dex). The distance modulus of the SMC was found to be <μ>= 18.90 ± 0.18 (std) from the RRab population in a distance scale where the distance modulus of the Large Magellanic Cloud (LMC) is μLMC= 18.52 ± 0.06 (std). The 1σ line-of-sight depth for the RRab stars was found to be σint= 4.13 ± 0.27 kpc, in good agreement with that estimated from red clump stars and eclipsing binaries. There is a clear indication that the metal-poorer and metal-richer objects in the sample may belong to different dynamical structures. The metal-rich stars have smaller scaleheight and could be part of a disc-like structure, while the more metal poor objects could be part of a much thicker structure, such as an inner halo or a bulge component.

New CCD light curves of the recently detected eclipsing variable GSC 4589-2999 were obtained and analysed using the Wilson-Deninney code. Spectroscopic observations of the system allowed the spectral classification of the components and the determination of their radial velocities. The physical properties and absolute parameters of the components and an updated ephemeris of the system are given.

We reexamined the total extinction along the sightline of a quasar (J004457+4123) behind the disk of M31 and used a varying total-to-selective extinction ratio in order to obtain a better agreement between its optical spectrum and a composite SDSS spectrum based on input spectra of quasars from DR7 at similar redshifts. The M31 outermost disk predominates (~85%) the total foreground (Milky Way+M31) selective extinction EB-V = 0.30+/-0.05 mag and the derived gas-to-dust ratio is N(H)/EB-V = (3.5+/-0.7)×1020 atcm-2 mag-1.

Aims: IKT 16 is an X-ray and radio-faint supernova remnant (SNR) in the Small Magellanic Cloud (SMC). A previous X-ray study of this SNR found a hard X-ray source near its centre. Using all available archival and proprietary XMM-Newton data, alongside new multi-frequency radio-continuum surveys and optical observations at Hα and forbidden [SII] and [OIII] lines, we aim to constrain the properties of the SNR and discover the nature of the hard source within. Methods: We combine XMM-Newton datasets to produce the highest quality X-ray image of IKT 16 to date. We use this, in combination with radio and optical images, to conduct a multi-wavelength morphological analysis of the remnant. We extract separate spectra from the SNR and the bright source near its centre, and conduct spectral fitting of both regions. Results: We find IKT 16 to have a radius of 37 ± 3 pc, with the bright source located 8 ± 2 pc from the centre. This is the largest known SNR in the SMC. The large size of the remnant suggests it is likely in the Sedov-adiabatic phase of evolution. Using a Sedov model to fit the SNR spectrum, we find an electron temperature kT of 1.03 ± 0.12 keV and an age of ≈14700 yr. The absorption found requires the remnant to be located deep within the SMC. The bright source is fit with a power law with index Γ = 1.58 ± 0.07, and is associated with diffuse radio emission extending towards the centre of the SNR. We argue that this source is likely to be the neutron star remnant of the supernova explosion, and infer its transverse kick velocity to be 580 ± 100 km s-1. The X-ray and radio properties of this source strongly favour a pulsar wind nebula (PWN) origin. Based on observations obtained with XMM-Newton, an ESA science mission with instruments and contributions directly funded by ESA Member States and NASA.

Aims: One of the goals of the XMM-Newton survey of the Small Magellanic Cloud is to study the Be/X-ray binary population. During one of our first survey observations, a bright new transient - XMMU J004814.0-732204 - was discovered. Methods: We present the analysis of the EPIC X-ray data, together with optical observations, to investigate the spectral and temporal characteristics of XMMU J004814.0-732204. Results: We found coherent X-ray pulsations in the EPIC data with a period of (11.86642 ± 0.00017) s. The X-ray spectrum can be modelled by an absorbed power law with an indication for a soft excess. Depending on the modelling of the soft X-ray spectrum, the photon index ranges between 0.53 and 0.66. We identify the optical counterpart as a B = 14.9 mag star that was monitored during the MACHO and OGLE-III projects. The optical light curves show regular outbursts by ~0.5 mag in B and R and up to 0.9 mag in I, which repeat on a time scale of about 1000 days. The OGLE-III optical colours of the star are consistent with an early B spectral type. An optical spectrum obtained at the 1.9 m telescope of the South African Astronomical Observatory in December 2009 shows Hα emission with an equivalent width of 3.5 ± 0.6 Å. Conclusions: The X-ray spectrum and the detection of pulsations suggest that XMMU J004814.0-732204is a new high-mass X-ray binary pulsar in the SMC. The long term variability and the Hα emission line in the spectrum of the optical counterpart identify it as a Be/X-ray binary system.

Aims: The largest Local Group spiral galaxy, M 31, has been completely imaged for the first time, obtaining a luminosity lower limit ~1035 erg s-1 in the 0.2-4.5 keV band. Our XMM-Newton EPIC survey combines archival observations along the major axis, from June 2000 to July 2004, with observations taken between June 2006 and February 2008 that cover the remainder of the D25 ellipse. The main goal of the paper is to study the X-ray source population of M 31. Methods: An X-ray catalogue of 1897 sources was created, with 914 detected for the first time. Source classification and identification were based on X-ray hardness ratios, spatial extent of the sources, and cross correlation with catalogues in the X-ray, optical, infrared, and radio wavelengths. We also analysed the long-term variability of the X-ray sources and this variability allows us to distinguish between X-ray binaries and active galactic nuclei (AGN). Furthermore, supernova remnant classifications of previous studies that did not use long-term variability as a classification criterion could be validated. Including previous Chandra and ROSAT observations in the long-term variability study allowed us to detect additional transient or at least highly variable sources, which are good candidate X-ray binaries. Results: Fourteen of the 30 supersoft source (SSS) candidates represent supersoft emission of optical novae. Many of the 25 supernova remnants (SNRs) and 31 SNR candidates lie within the 10 kpc dust ring and other star-forming regions in M 31. This connection between SNRs and star-forming regions implies that most of the remnants originate in type II supernovae. The brightest sources in X-rays in M 31 belong to the class of X-ray binaries (XRBs). Ten low-mass XRBs (LMXBs) and 26 LMXB candidates were identified based on their temporal variability. In addition, 36 LMXBs and 17 LMXB candidates were identified owing to correlations with globular clusters and globular cluster candidates. From optical and X-ray colour-colour diagrams, possible high-mass XRB (HMXB) candidates were selected. Two of these candidates have an X-ray spectrum as is expected for an HMXB containing a neutron star primary. Conclusions: While our survey has greatly improved our understanding of the X-ray source populations in M 31, at this point 65% of the sources can still only be classified as "hard" sources; i.e. it is not possible to decide whether these sources are X-ray binaries or Crab-like supernova remnants in M 31 or X-ray sources in the background. Deeper observations in X-ray and at other wavelengths would help classify these sources. Based on observations obtained with XMM-Newton, an ESA science mission with instruments and contributions directly funded by ESA Member States and NASA.Tables 5 and 8 are only available in electronic form at the CDS via anonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/534/A55

Context. Classical novae (CNe) represent the major class of supersoft X-ray sources (SSSs) in the central region of the galaxy M 31. Aims: We performed a dedicated monitoring of the M 31 central region with XMM-Newton and Chandra between Nov. 2007 and Feb. 2008 and between Nov. 2008 and Feb. 2009, respectively, to find SSS counterparts of CNe, determine the duration of their SSS phase, and derive physical outburst parameters. Methods: We systematically searched our data for X-ray counterparts of CNe, determined their X-ray light curves and characterised their spectra using blackbody fits and white dwarf (WD) atmosphere models. Additionally, we determined luminosity upper limits for all previously known X-ray emitting novae that are not detected any more and for all CNe in our field of view with optical outbursts between one year before the start of the X-ray monitoring (Oct. 2006) and its end (Feb. 2009). Results: We detected 17 X-ray counterparts of CNe in M 31, only four of which were previously known. These latter sources are still active 12.5, 11.0, 7.4 and 4.8 years after the optical outburst. In addition, we detected three known SSSs without a nova counterpart. Four novae displayed short SSS phases (<100 d). Based on these results and previous studies we compiled a catalogue of all novae with SSS counterparts in M 31 known so far. We used this catalogue to derive correlations between the following X-ray and optical nova parameters: turn-on time, turn-off time, blackbody temperature (X-ray), t2 decay time and expansion velocity of the ejected envelope (optical). Temperatures derived from blackbody fits and WD atmosphere models were found to characterise the effective SSS temperatures almost equally well. Furthermore, we found a first hint for the existence of a difference between SSS parameters of novae associated with the stellar populations of the M 31 bulge and disk. Additionally, we conducted a Monte Carlo Markov chain simulation on the intrinsic fraction of novae with SSS phase. This simulation showed that the high fraction of novae without detected SSS emission might be explained by the inevitably incomplete coverage with X-ray observations in combination with a large part of novae with short SSS states, as expected from the WD mass distribution. Conclusions: Our results confirm that novae are the major class of SSSs in the central region of M 31. The catalogue of novae with X-ray counterpart, mainly based on our X-ray monitoring, contains valuable insight into the physics of the nova process. In order to verify our results with an increased sample, more monitoring observations are needed. Partly based on observations with XMM-Newton, an ESA Science Mission with instruments and contributions directly funded by ESA Member States and NASA.All tables are available in electronic form at http://www.aanda.orgTable 9 is also available at the CDS via anonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/533/A52

The largest Local Group spiral galaxy, M31, has been completely imaged for the first time, obtaining a luminosity lower limit about 1035erg/s in the 0.2-4.5keV band. Our XMM-Newton EPIC survey combines archival observations along the major axis, from June 2000 to July 2004, with observations taken between June 2006 and February 2008 that cover the remainder of the D25 ellipse. The main goal of the paper is to study X-ray source populations of M31. An X-ray catalogue of 1897(*) sources was created with 914 detected for the first time. Source classification and identification were based on X-ray hardness ratios, spatial extent of the sources, and cross correlation with catalogues in the X-ray, optical, infrared and radio wavelengths. We also analysed the long-term variability of the X-ray sources and this variability allows us to distinguish between X-ray binaries and active galactic nuclei (AGN). Furthermore, supernova remnant classifications of previous studies that did not use long-term variability as a classification criterion could be validated. Including previous Chandra and ROSAT observations in the long-term variability study allowed us to detect additional transient or at least highly variable sources, which are good candidate X-ray binaries. (*) the final catalog of table5 icludes 1948 sources. (2 data files).

Context. Classical novae (CNe) represent the major class of supersoft X-ray sources (SSSs) in the central region of the galaxy M31. We performed a dedicated monitoring of the M31 central region with XMM-Newton and Chandra between Nov 2007 and Feb 2008 and between Nov 2008 and Feb 2009, respectively, to find SSS counterparts of CNe, determine the duration of their SSS phase, and derive physical outburst parameters. We systematically searched our data for X-ray counterparts of CNe, determined their X-ray light curves and characterised their spectra using blackbody fits and white dwarf (WD) atmosphere models. Additionally, we determined luminosity upper limits for all previously known X-ray emitting novae that are not detected any more and for all CNe in our field of view with optical outbursts between one year before the start of the X-ray monitoring (Oct 2006) and its end (Feb 2009). (2 data files).

A deep XMM survey has identified hundreds of bright X-ray sources from the direction of Andromeda. These sources are mostly comprised of supernova remnants, X-ray Binaries and background Active Galactic Nuclei (AGN). We have obtained 35 optical spectra of their candidate counterparts using the 3.5-meter telescope at the Apache Point Observatory. After calibrating and extracting the objects' spectra from the sky background, we've been able to classify 8 as background AGN with red shifts (1.15< z <2.11). Preliminary classifications of the 27 others include 9 stars in Andromeda and 1 supernova remnant in Andromeda. With these results we are beginning to constrain the background contamination in the XMM survey and to find good high-mass X-ray binary candidates in Andromeda. Furthermore, future high-resolution spectroscopy of the background AGN may allow detailed absorption studies of the Andromeda interstellar medium. Support for this work has been provided by NASA grant NNX06AF58G, through the XMM-Newton Guest Observer Facility.

Aims: We announce the discovery of a quasar behind the disk of M 31, which was previously classified as a remarkable nova in our neighbour galaxy. It is shown here to be a quasar with a single strong flare where the UV flux has increased by a factor of 20. The present paper is primarily aimed at the remarkable outburst of J004457+4123 (Sharov 21), with the first part focussed on the optical spectroscopy and the improvement in the photometric database. Methods: We exploited the archives of photographic plates and CCD observations from 15 wide-field telescopes and performed targetted new observations. In the second part, we try to fit the flare by models of (1) gravitational microlensing due to a star in M 31 and (2) a tidal disruption event (TDE) of a star close to the supermassive black hole of the quasar. Results: Both the optical spectrum and the broad band spectral energy distribution of Sharov 21 are shown to be very similar to that of normal, radio-quiet type 1 quasars. We present photometric data covering more than a century and resulting in a long-term light curve that is densely sampled over the past five decades. The variability of the quasar is characterized by a ground state with typical fluctuation amplitudes of 0.2 mag around bar{B} 20.5, superimposed by a singular flare of 2 yr duration (observer frame) with the maximum at 1992.81. The total energy in the flare is at least three orders of magnitudes higher than the radiated energy of the most luminous supernovae, provided that it comes from an intrinsic process and the energy is radiated isotropically. The profile of the flare light curve is asymmetric showing in particular a sudden increase before the maximum, whereas the decreasing part can be roughly approximated by a t-5/3 power law. Both properties appear to support the standard TDE scenario where a 10 M_⊙ giant star was shredded in the tidal field of a 2...5×108 M_⊙ black hole. The short fallback time derived from the observed light curve requires an ultra-close encounter where the pericentre of the stellar orbit is deep within the tidal disruption radius. This simple model neglects, however, the influence of the massive accretion disk, as well as general-relativistic effects on the orbit of the tidal debris. Gravitational microlensing probably provides an alternative explanation, although the probability of such a high amplification event is very low.

Using Chandra, XMM-Newton and optical data we study the young (?Myr) X-ray binary (XRB) populations of the Magellanic Clouds. We find that the Be-XRBs of the Small Magellanic Cloud (SMC) are observed in regions with star formation (SF) rate bursts ˜25-60 Myr ago. The similarity of this age with the age of maximum occurrence of the Be phenomenon (˜40 Myr) indicates that the presence of a circumstellar decretion disk plays a significant role in the number of observed XRBs in the 10-100 Myr age range. We also find that regions with strong but more recent SF (e.g. the Wing) are deficient in Be-XRBs. By correlating the number of observed Be-XRBs with the formation rate of their parent populations, we measure a Be-XRB production rate of ˜1 system per 10^{-6} M⊙/yr. Finally, we use the strong localization of the Be-XRB systems in order to set limits on the kicks imparted on the neutron star during the supernova explosion. Understanding of the populations of compact objects and their connection with star-formation (SF) will allow us to investigate channels of XRB formation in a variety of environments and therefore help in studies of the X-ray source populations of star-forming galaxies outside our Local Group, and even enable their use as a SF diagnostic. This work was supported from NASA LTSA grant NAG5-13056, and NASA grant GO2-3117X.

Classical novae (CNe) have recently been reported to represent the major class of supersoft X-ray sources (SSSs) in the central area of our neighbouring galaxy M 31. This paper presents a review of results from recent X-ray observations of M 31 with XMM-Newton and Chandra. We carried out a dedicated optical and X-ray monitoring program of CNe and SSSs in the central area of M 31. We discovered the first SSSs in M 31 globular clusters (GCs) and their connection to the very first discovered CN in a M 31 GC. This result may have an impact on the CN rate in GCs. Furthermore, in our optical and X-ray monitoring data we discovered the CN M31N 2007-11a, which shows a very short SSS phase of 29-52 days. Short SSS states (durations ≤ 100 days) of CNe indicate massive white dwarfs (WDs) that are candidate progenitors of supernovae type Ia. In the case of M31N 2007-11a, the optical and X-ray light curves suggest a binary containing a WD with M_WD > 1.0 M\sun. Finally, we present the discovery of the SSS counterpart of the CN M31N 2006-04a k. The X-ray light curve of M31N 2006-04a shows short-time variability, which might indicate an orbital period of about 2 hours. Partly based on observations with \xmmk, an ESA Science Mission with instruments and contributions directly funded by ESA Member States and NASA.

To investigate the transient nature of supersoft sources (SSSs) in M 31, we compared SSS candidates of the XMM-Newton Deep Survey, ROSAT PSPC surveys and the Chandra catalogues in the same field. We found 40 SSSs in the XMM-Newton observations. While 12 of the XMM-Newton sources were brighter than the limiting flux of the ROSAT PSPC survey, only two were detected with ROSAT ˜10 yr earlier. Five correlate with recent optical novae which explains why they were not detected by ROSAT. The remaining 28 XMM-Newton SSSs have fluxes below the ROSAT detection threshold. Nevertheless we found one correlation with a ROSAT source, which had significantly larger fluxes than during the XMM-Newton observations. Ten of the XMM-Newton SSSs were detected by Chandra with <1- ˜6 yr between the observations. Five were also classified as SSSs by Chandra. Of the 30 ROSAT SSSs three were confirmed with XMM-Newton, while for 11 sources other classifications are suggested. Of the remaining 16 sources one correlates with an optical nova. Of the 42 Chandra very-soft sources five are classified as XMM-Newton SSSs, while for 22 we suggest other classifications. Of the remaining 15 sources, nine are classified as transient by Chandra, one of them correlates with an optical nova. These findings underlined the high variability of the sources of this class and the connection between SSSs and optical novae. Only three sources, were detected by all three missions as SSSs. Thus they are visible for more than a decade, despite their variability. Based on observations obtained with XMM-Newton, an ESA science mission with instruments and contributions directly funded by ESA Member States and NASA.

Using Chandra, XMM-Newton and optical photometric catalogs we study the young XRB populations of the SMC. We find that the Be-XRBs are observed in regions with star formation (SF) rate bursts ˜25-60 Myr ago. The similarity of this age with the age of maximum occurrence of the Be phenomenon (˜40 Myr) indicates that the presence of a circumstellar decretion disk plays a significant role in the number of observed XRBs in the 10-100 Myr age range. We also find that regions with strong but more recent SF (e.g. the Wing) are deficient in Be-XRBs. By correlating the number of observed Be-XRBs with the formation rate of their parent populations, we measure a Be-XRB production rate of ˜1 system per 10-6 Msun/yr. Finally, we use the strong localization of the Be-XRB systems in order to set limits on the kicks imparted on the neutron star during the supernova explosion.

We derive metal abundances ([Fe/H]) of 472 RR-Lyrae variables of RRab type in the Small Magellanic Cloud (SMC), based on extended and merged data provided by the OGLE II and OGLE III projects. Fourier decomposition of the 11-year V-band light curves of the variables and Monte Carlo simulations have been used to derive Fourier parameters which are related to [Fe/H]. We examine possible correlations between [Fe/H] and projected distance from the dynamical center (DC) of the SMC. We also derive the distance along the line of sight of the RR-Lyrae variables which represent the old populations in the SMC. (Kapakos et al., in prep.)

As one of the initiatives undertaken to promote Astronomy in Greece, particularly in view of the International Year of Astronomy 2009, the Hellenic Astronomical Society (Hel.A.S.), in collaboration with the Hellenic Association of the Laboratory Centers of Physical Sciences, organized a special workshop, under the umbrella of the 9th Hellenic Astronomical Conference, addressed to school teachers. The aim was to develop and promote teaching of Astronomy, which is currently an optional subject, offered during the second year of senior high school (Lyceum).

Pietsch, Henze, and Burwitz -- together with A. Liakos (Department of Physics, University of Athens), D. Hatzidimitriou (Department of Physics, University of Crete), and P. Niarchos (Department of Physics, University of Athens) -- add that confirmation of M31N 2010-06c at mag 18.0 was obtained with a stack of ten 60-s unfiltered CCD images obtained with a 40-cm Cassegrain telescope (+ f/5.1 focal reducer + 2184x1472-pixel ST-10XME CCD camera; pixel size 6.8 microns square) at the Athens University Observatory on June 27.028 UT; they provide position end figures 04s.48, 33".8.

Using Chandra, XMM-Newton, and optical photometric catalogs we study the young X-ray binary (XRB) populations of the Small Magellanic Cloud. We find that the Be/X-ray binaries (Be-XRBs) are observed in regions with star formation rate bursts ~25-60 Myr ago. The similarity of this age with the age of maximum occurrence of the Be phenomenon (~40 Myr) indicates that the presence of a circumstellar decretion disk plays a significant role in the number of observed XRBs in the 10-100 Myr age range. We also find that regions with strong but more recent star formation (e.g., the Wing) are deficient in Be-XRBs. By correlating the number of observed Be-XRBs with the formation rate of their parent populations, we measure a Be-XRB production rate of ~1 system per 3 × 10-3 M sun yr-1. Finally, we use the strong localization of the Be-XRB systems in order to set limits on the kicks imparted on the neutron star during the supernova explosion.

The business session for Commission 37 was held on 11 August 2009 at the IAU General Assembly in Rio de Janeiro. The meeting was attended by about a dozen members of our Comission, including President Elmegreen, VP Carraro and several committee members. We introduced ourselves and then went through a powerpoint presentation first prepared by outgoing President Hatzidimitriou and revised by incoming President Elmegreen. The contents of the powerpoint presentation are given in this summary.

Division VII provides a forum for astronomers studying the Milky Way Galaxy and its constituents. Several meetings directly relevant to his subject were held at the General Assembly in Rio: IAU Symp. 262 Stellar Populations, IAU Symp. 265 Chemical Abundances in the Universe, IAU Symp. 266 Star Clusters, Joint Discussion 5 Modeling the Milky Way in the Era of Gaia, and Special Session 5 The Galactic Plane. Division VII therefore did not organize a separate science session at Rio, but business meetings were held for both the Division and for Commissions 33 and 37.

Context. Classical novae (CNe) have recently been reported to represent the major class of supersoft X-ray sources (SSSs) in the central region of our neighbour galaxy M 31. Aims: We carried out a dedicated monitoring of the M 31 central region with XMM-Newton and Chandra in order to find SSS counterparts of CNe, determine the duration of their SSS phase and derive physical outburst parameters. Methods: We systematically searched our data for X-ray counterparts of CNe and determined their X-ray light curves and spectral properties. Additionally, we determined luminosity upper limits for all novae from previous studies which are not detected anymore and for all CNe in our field of view with optical outbursts between May 2005 and March 2007. Results: We detected eight X-ray counterparts of CNe in M 31, four of which were not previously known. Seven sources can be classified as SSSs, one is a candidate SSS. Two SSSs are still visible more than nine years after the nova outburst, whereas two other nova counterparts show a short SSS phase of less than 150 days. Of the latter sources, M31N 2006-04a exhibits a short-time variable X-ray light curve with an apparent period of (1.6±0.3) h. This periodicity could indicate the binary period of the system. There is no X-ray detection for 23 out of 25 CNe which were within the field of view of our observations and had their outburst from about one year before the start of the monitoring until its end. From the 14 SSS nova counterparts known from previous studies, ten are not detected anymore. Additionally, we found four SSSs in our XMM-Newton data without a nova counterpart, one of which is a new source. Conclusions: Out of eleven SSSs detected in our monitoring, seven are counterparts of CNe. We therefore confirm the earlier finding that CNe are the major class of SSSs in the central region of M 31. We use the measured SSS turn-on and turn-off times to estimate the mass ejected in the nova outburst and the mass burned on the white dwarf. Classical novae with short SSS phases seem to be an important contributor to the overall population. Partly based on observations with XMM-Newton, an ESA Science Mission with instruments and contributions directly funded by ESA Member States and NASA.

We confirm a nova candidate in M 31 reported to us by K. Nishiyama and F. Kabashima and present a pre-discovery detection and upper limit that allows us to tightly constrain the time of outburst for this object. New observations show that the source is still increasing in brightness. The nova candidate was discovered by Nishiyama and Kabashima (Miyaki-Argenteus observatory, Japan) on 2010 September 30.566 UT, with no object visible at its position on September 28.606 UT (private communication).

We report the detection of seven recent nova candidates in M 31 on two sets of three 300 s dithered stacked CCD images obtained on 2010 Oct 4 with the 1.3m Ritchey Chretien f/7.5 telescope at Skinakas Observatory, Crete, Greece, using an Andor DZ436-BV CCD Camera (with a Marconi 2k x 2k chip with 13.5 microns sq. pixels) and a broad (75 Angstrom wide) H-alpha filter. Only novae M31N 2010-07a and M31N 2010-10a were also detected on four 100 s dithered stacked CCD images obtained on 2010 Oct 5 with the same telescope and camera using a R filter.

W. Pietsch, M. Henze, and V. Burwitz, Max-Planck-Institut fuer Extraterrestrische Physik; A. Liakos, Department of Physics, University of Athens; D. Hatzidimitriou, Department of Physics, University of Crete; and P. Niarchos, Department of Physics, University of Athens, report the detection of an apparent nova in M31 using observations with the UltraViolet/Optical Telescope (UVOT) onboard the Swift satellite. The object was serendipitously detected in the UVW1 filter (range 181-321 nm; UVOT observation number 31255018 with 4333-s exposure) starting on June 24.02 UT with a magnitude of 19.5 +/- 0.2. The position for the nova candidate, designated M31N 2010-06d, is R.A. = 0h42m55s.56, Decl. = +41d19'25".5 (equinox 2000.0; uncertainty 1".0), which is 127" east and 197" north of the core of M31. The source is clearly detected in the individual images. In the UVW1 filter, Swift observation number 31255014, starting on June 12.04 (4161-s exposure), and in the U filter, Swift observation number 31255017, starting on June 21.29 (1330-s exposure), no object was detected at the position of M31N 2010-06d, with limiting magnitudes of 20.5 and 19.7 (3 sigma), respectively. (All magnitudes are on the UVOT photometric system of Poole et al. 2008, MNRAS 383, 627, and have not been corrected for extinction.) M31N 2010-06d was confirmed on a stacked unfiltered CCD image composed of ten 60-s frames obtained at a 40-cm Cassegrain telescope with a focal reducer (f/5.1) equipped with a 2184x1472-pixel ST-10XME CCD camera (pixel size 6.8 microns square) at the Athens University Observatory on July 1.082 UT, yielding magnitude 17.8 (obtained from a photometric solution using R magnitudes of the Local Group Survey M31 catalogue of Massey et al. 2006) and position end figures 55s.62, 25".7 (uncertainty 0".5), fully consistent with the position of the Swift source. M31N 2010-06d is visible in the UV filter already several days before the detection in the optical (similar to novae M31N 2009-08a and M31N 2010-01b). Public data from the Swift data archive was used. Kamil Hornoch, Ondrejov Observatory, reports the independent discovery of M31N 2010-06d by Marek Wolf and himself on co-added 1620-s and co-added 1350-s R-band CCD frames taken by Hornoch on June 30.003 UT and by Wolf on July 1.022, respectively, with the 0.65-m telescope at Ondrejov. M31N 2010-06d is marginally visible on single images used for the co-added frames. Also, the new object is visible on pre-discovery co-added R-band frames taken with the same instrumentation during three previous nights, but is not present on numerous archive images taken at Ondrejov. M31N 2010-06d is located at R.A. = 0h42m55s.53, Decl. = +41o19'25".0 (equinox 2000.0), which is 126" east and 196" north of the center of M31. Available R-band magnitudes for M31N 2010-06d, measured by Hornoch: June 9.459 UT, [21.7 (P. Garnavich, C. Littlefield, N. Paul, and S. Bouzid, 1.83-m Vatican Advanced Technology Telescope); 18.152, [21.1 (P. Kubanek, J. Gorosabel, O. Lara-Gil, and M. Jelinek, 1.23-m telescope at Calar Alto); 27.034, 20.1 +/- 0.3 (K. Hornoch, 0.65-m telescope at Ondrejov); 28.014, 19.7 +/- 0.2 (Hornoch and P. Hornochova, 0.65-m telescope at Ondrejov); 28.040, 19.7 +/- 0.2 (Hornoch and Hornochova); 29.022, 19.2 +/- 0.2 (P. Zasche, 0.65-m telescope at Ondrejov); 29.034, 19.0 +/- 0.2 (Zasche); 30.003, 18.6 +/- 0.15 (Hornoch); 30.022, 18.65 +/- 0.1 (Hornoch); July 1.022, 18.3 +/- 0.1 (M. Wolf, 0.65-m telescope at Ondrejov).

We report the detection of a nova candidate in M 31 using observations with the UltraViolet/Optical Telescope (UVOT) on board the Swift satellite. The object was serendipitously detected in the UVW1 filter (181-321nm) UVOT observation 00031255018 with 4333 s exposure starting on 2010-06-24.02 UT with a magnitude of 19.5+-0.2. The position for the nova candidate is RA = 00h42m55s.56, Dec = +41d19'25".5 (J2000, accuracy of 1.0"), which is 127" east and 197" north of the core of M 31.

We report the discovery of a possible nova in M 31 on two 10x60s stacked unfiltered CCD images obtained a 40-cm Cassegrain telescope with a focal reducer (F/5.1) equipped with a 2184 x 1472 pixel ST-10XME CCD camera (pixel size 6.8 microns square) at the Athens University Observatory, Greece on 2009 June 30.045 UT and July 1.049 UT with magnitudes of 17.7 and 17.5, respectively. The position of the nova candidate is RA = 00h42m10.36s, Dec = +41o12'19.9" (J2000, accuracy 0.3"), which is 383" west and 229" south of the core of M 31.

We present the most likely optical counterparts of 113 X-ray sources detected in our Chandra survey of the central region of the Small Magellanic Cloud (SMC) based on the OGLE-II and Magellanic Clouds Photometric Survey catalogs. We estimate that the foreground contamination and chance coincidence probability are minimal for the bright optical counterparts (corresponding to OB type stars; 35 in total). We propose here for the first time 13 high-mass X-ray binaries, of which four are Be/X-ray binaries (Be-XRBs), and we confirm the previous classification of 18 Be-XRBs. We estimate that the new candidate Be-XRBs have an age of ~15-85 Myr, consistent with the age of Be stars. We also examine the "overabundance" of Be-XRBs in the SMC fields covered by Chandra, in comparison with the Galaxy. In luminosities down to ~1034 erg s-1, we find that SMC Be-XRBs are ~1.5 times more common when compared to the Milky Way even after taking into account the difference in the formation rates of OB stars. This residual excess can be attributed to the lower metallicity of the SMC. Finally, we find that the mixing of Be-XRBs with other than their natal stellar population is not an issue in our comparisons of Be-XRBs and stellar populations in the SMC. Instead, we find indication for variation of the SMC XRB populations on kiloparsec scales, related to local variations of the formation rate of OB stars and slight variation of their age, which results in different relative numbers of Be stars and therefore XRBs.

Using Chandra, XMM-Newton and optical photometric catalogs we study the young X-ray binary (XRB) populations of the Small Magellanic Cloud (SMC). We find that the Be/X-ray binaries (Be-XRBs) are observed in regions with star-formation (SF) rate bursts ~30-70 Myr ago, which coincides with the age of maximum Be-star formation, while regions with strong but more recent SF (e.g., the Wing) are deficient in Be-XRBs. Using the 2dF spectrograph of the Anglo-Australian Telescope (AAT) we have obtained optical spectra of 20 High-Mass X-ray Binaries (HMXBs) in the SMC. All of these sources were proved to be Be-XRBs. Similar spectral-type distributions of Be-XRBs and Be field stars in the SMC have been found. On the other hand, the Be-XRBs in the Galaxy follow a different distribution than the isolated Be stars in the Galaxy, in agreement with previous studies.

The RACE-OC project, standing for Rotation and Activity Evolution in Open Clusters, is a long-term project aimed at studying the evolution of rotation and magnetic activity of late-type members of stellar open clusters. Magnetic fields play a fundamental role in altering the rotational properties of late-type stars. They are responsible, e.g., for angular momentum loss in the wind or its redistribution in the stellar interior. Magnetic fields in late-type stars and their related phenomena, such as photospheric cool spots and bright faculae, chromospheric plages, and X-ray emission, in turn depend on the stellar rotation which controls the efficiency of the hydromagnetic dynamo. Thus, the evolution of angular momentum and magnetic activity offer complementary approaches to understanding the mechanisms by which rotation and magnetic fields influence each other in late-type stars.

Star clusters are valuable tools for theoretical and observational astronomy across a wide range of disciplines from cosmology to stellar spectroscopy. For example, properties of globular clusters are used to constrain stellar evolutionary models, nucleosynthesis and chemical evolution, as well as the star formation and assembly histories of galaxies and the distribution of dark matter in present-day galaxies. Open clusters are widely used as stellar laboratories for the study of specific stellar phenomena (e.g., various emission-line stars, pulsating pre-MS stars, magnetic massive stars, binarity, stellar rotation, etc.). They also provide observational constraints on models of massive star evolution and of Galactic disk formation and chemical evolution.

Division VII gathers astronomers studying the diffuse matter in space between stars, ranging from primordial intergalactic clouds, via dust and neutral and ionized gas in galaxies, to the densest molecular clouds and the processes by which stars are formed.

We present a large sample (20 in total) of optical spectra of Small Magellanic Cloud (SMC) High-Mass X-ray Binaries obtained with the 2dF spectrograph at the Anglo-Australian Telescope. All of these sources are found to be Be/X-ray binaries (Be-XRBs), while for five sources we present original classifications. Several statistical tests on this expanded sample support previous findings for similar spectral-type distributions of Be-XRBs and Be field stars in the SMC, and of Be-XRBs in the Large Magellanic Cloud and the Milky Way, although this could be the result of small samples. On the other hand, we find that Be-XRBs follow a different distribution than Be stars in the Galaxy, also in agreement with previous studies. In addition, we find similar Be spectral-type distributions between the Magellanic Clouds samples. These results reinforce the relation between the orbital period and the equivalent width of the Hα line that holds for Be-XRBs. SMC Be stars have larger Hα equivalent widths when compared to Be-XRBs, supporting the notion of circumstellar disk truncation by the compact object.

Context: A recent survey of the Local Group spiral galaxy M 31 with XMM-Newton yielded a large number of X-ray sources. Aims: This is the second in a series of papers with the aim of identifying the optical counterparts of these X-ray sources. Methods: We have obtained optical spectra for 21 bright optical counterparts of 20 X-ray sources in the direction of M 31, using the 1.3-m Skinakas telescope in Crete, Greece. Results: For 17 of the 20 X-ray sources, we have identified the optical counterpart as a normal late type star (of type F or later) in the foreground (i.e. in the Milky Way). For two more sources, there were two possible optical counterparts, in each case, while two more objects have X-ray properties that are not compatible with the spectral characteristics of late type non-flaring stars.

We confirm a nova candidate in M 31 reported to us by K. Nishiyama and F. Kabashima and present a pre-discovery detection that allows us to tightly constrain the time of outburst for this object. The nova candidate was discovered by Nishiyama and Kabashima (Miyaki-Argenteus observatory, Japan) on 2009 September 3.752 UT, with no object visible at its position on September 1.566 UT (private communication).

Using Chandra, XMM-Newton and optical photometric and spectroscopic catalogs we study the young (<100 Myr) X-ray binary populations of the Small Magellanic Cloud, which at ˜60 kpc is our second nearest star-forming galaxy. In particular, we investigate the importance of Be/X-ray binaries as a dominant component of young X-ray binary populations, based on a study of the connection between X-ray source populations and their parent stellar populations. We find that a significant number of Be/X-ray binaries and/or pulsars are connected with a burst of star formation ˜25-60 Myr ago, while regions with weak star-formation rate at ˜42 Myr, such as the SMC Wing, are deficient in Be/X-ray binaries. We argue that the very strong similarity between the age of maximum occurence of Be stars and the age of the parent populations of X-ray binaries in the Small Magellanic Cloud indicates that the Be phenomenon plays a significant role in the number of X-ray binary populations in this age range. Finally, based on the spatial correlation between the star-formation activity and the X-ray binaries, we set a limit on their kick velocity of ˜15-20 km/s, while there is strong indication for velocities of even a factor of two lower, and we estimate a Be/X-ray binary production rate of ˜1 system per 10^{-6} M_{⊙}/yr.

We report the discovery of a possible nova in M 31 on four consecutive dithered stacked 100s R filter CCD images, obtained on 2008 July 06.04, with the 1.3m Ritchey Chretien f/7.5 telescope at Skinakas Observatory, Crete, Greece, using an Andor DZ436-BV CCD Camera (with a Marconi 2k x 2k chip with 13.5μm sq. pixels). The R magnitude of the object was 18.7. The object is already visible with a magnitude of 18.3 on a 12*60s stacked R filter CCD image obtained with the robotic 60cm telescope with an E2V CCD (2kx2k) of the Livermore Optical Transient Imaging System (Super-LOTIS, located at Steward Observatory, Kitt Peak, Arizona, USA) on 2008 June 30.45.

We carried out spectroscopic observations of the optical transient near M31 reported in ATel #1591 (RA = 0h42m27s.81 DEC =+41o14'48".2 (J2000)) from the 1.3m telescope of the Skinakas Observatory in Crete (Greece) on the nights 27 June 2008 and 2 July 2008. The spectra covered the range 5080-7160 angstroms. The Halpha appeared strongly in emission and displayed a double peaked profile. The ratio of the blue peak to the red peak (B/R) reversed from B > R (i.e blue-dominated profile) on 27 June to B < R (i.e red-dominated profile) on 2 July.

Using Chandra, XMM and optical data (both photometric and spectroscopic), we studied the X-ray binary population in the Small Magellanic Cloud (SMC), down to an X-ray luminosity of ~4×10^33 erg s-1, thus allowing the investigation of the faintest of the high-mass Xraybinary populations. The regions were selected so as to have varying star formation histories, in order to investigate, using homogeneous and well defined samples, the connection between the Be- XRB phenomenon and SF history. The characterization of the X-ray sources discovered in our Chandra and XMM surveys and the selection of our sample of Be-XRBs, was based on a combination of X-ray and optical properties. We found that the number of Be/X-ray binaries (Be-XRBs) peaks at the age of 40-70 Myr ago. Finally, we constructed their X-ray luminosity function (XLF). There are very few X-ray sources above ~10^35 ergs^-1, which is consistent with the transient nature of Be X-ray binaries. There is also indication for a flattening of the XLF at ~10^35 ergs^-1, which would be consistent with the onset of the propeller effect.

Using Chandra, XMM-Newton and optical data (published photometric catalogs and our 2dF spectroscopic survey) we study the X-ray binary (XRB) populations of the Small Magellanic Cloud (SMC). We find that the number of Be/X-ray binaries (Be-XRBs) peaks at the age of maximum Be-star formation ~30-70 Myr ago. We also examine the ``overabundance'' of Be-XRBs in the SMC fields covered by Chandra, in comparison with the Milky Way. Even after taking into account the difference in the formation rate of OB stars, we estimate that Be-XRBs are ~2 times more common in the SMC when compared to the Milky Way and for luminosities down to ~1034 erg s-1. We explain this large number of SMC Be-XRBs as the result of both its low metallicity environment (~1/5 solar) and its high star-formation (SF) rate at the age of maximum formation of Be stars.

We present a detailed analysis of three globular cluster X-ray sources in the XMM-Newton extended survey of M31. The X-ray counterpart to the M31 globular cluster Bo 45 (XBo 45) was observed with XMM-Newton on 2006 December 26. Its combined pn+MOS 0.3-10 keV light curve was seen to vary by ~10%, and its 0.3-7.0 keV emission spectrum was well described by an absorbed power law with photon index 1.44 +/- 0.12. Its variability and emission is characteristic of low-mass X-ray binaries (LMXBs) in the low-hard state, whether the accretor is a neutron star or black hole. Such behavior is typically observed at luminosities lesssim10% Eddington. However, XBo 45 exhibited this behavior at an unabsorbed, 0.3-10 keV luminosity of 2.5 +/- 0.2 × 1038 erg s-1, or ~140% Eddington for a 1.4 M⊙ neutron star accreting hydrogen. Hence, we identify XBo 45 as a new candidate black hole LMXB. XBo 45 appears to have been consistently bright for ~30 years, consistent with theoretical prediction for a globular cluster black hole binary formed via tidal capture. Bo 375 was observed in the 2007 January 2 XMM-Newton observation, and has a two-component spectrum that is typical for a bright neutron star LMXB. Bo 135 was observed in the same field as Bo 45, and could contain either a black hole or a neutron star.

We report the discovery of a new nova in M 31 on four consecutive dithered stacked R filter CCD images, obtained on 2008 Oct 18.91, with the 1.3m Ritchey Chretien f/7.5 telescope at Skinakas Observatory, Crete, Greece, using an Andor DZ436-BV CCD Camera (with a Marconi 2k x 2k chip with 13.5µm sq. pixels). The R magnitude of the object was 18.3. The object is already visible on several earlier R images obtained with the same telescope and camera.

Aims: The purpose of this study is to find transient X-ray sources in M 31 and to investigate and classify their nature. Methods: Three X-ray transients were observed with Swift. For each of the three X-ray transients, we used the Swift X-ray and optical data with observations from XMM-Newton and Chandra to investigate the lightcurves and the spectra of the outburst, thereby identifying the source types. Results: The outburst of XMMU J004215.8+411924 lasted about one month. The source had a hard power-law spectrum with a photon index of 1.6. It was previously identified as a Be/X-ray binary based on the optical identification with a star. However, we show that, with improved source coordinates it is clear that the optical source is not the counterpart to the X-ray source. The source SWIFT J004217.3+411532 had a bright outburst, after which it slowly decayed over half a year. The spectrum was soft, corresponding to a thermal accretion disc with an innermost temperature of ~250-600 eV. The source was not seen in the optical, and the soft spectrum indicates that the source is most likely a black-hole low-mass X-ray binary. M31N 2006-11a is a nova that was previously observed in the optical. We detected it both in X-rays and UV with Swift ~half a year after the optical maximum, after which it decayed below the Swift detection threshold within a month. The spectrum of the X-ray transient can be modelled by a black-body with a temperature of 50 eV. We use catalogues of X-ray transients in M 31 to estimate their rate, and we find a lower limit of 9 yr-1.

We report the discovery of two new, bright possible novae in M 31 on dithered stacked R filter CCD images, obtained on 2008 August 09, with the 1.3m Ritchey Chretien f/7.5 telescope at Skinakas Observatory, Crete, Greece, using an Andor DZ436-BV CCD Camera (with a Marconi 2k x 2k chip with 13.5µm sq. pixels). The first object is visible in two different pointings of four images taken on 2008 August 09.96 and three images taken on 2008 August 09.97, respectively.

Context: Classical novae are quite frequent in M 31. However, very few spectra of M 31 novae have been studied to date, especially during the early decline phase. Aims: Our aim is to study the photometric and spectral evolution of a M 31 nova event close to outburst. Methods: Here, we present photometric and spectroscopic observations of M31N 2005-09c, a classical nova in the disk of M 31, using the 1.3 m telescope of the Skinakas Observatory in Crete (Greece), starting on the 28th September, i.e. about 5 days after outburst, and ending on the 5th October 2005, i.e. about 12 days after outburst. We also have supplementary photometric observations from the La Sagra Observatory in Northern Andalucía, Spain, on September 29 and 30, October 3, 6 and 9 and November 1, 2005. The wavelength range covered by the spectra is from 3565 Å to 8365 Å. The spectra are of high S/N allowing the study of the evolution of the equivalent widths of the Balmer lines, as well as the identification of non-Balmer lines. Results: The nova displays a typical early decline spectrum that is characterized by many weak Fe II multiplet emissions. It is classified as a Pfe nova. From the nova light curve, we have also derived its speed class, t_2=14±2.5 days. As the nova evolved the Balmer lines became stronger and narrower. The early decline of the expansion velocity of the nova follows a power law in time with an exponent of ≃-0.2.

We report the discovery of an optical nova candidate in M 31 on ten stacked R filter CCD images (each with 60 sec exposure) obtained on 2007 Aug 30.018 with an R magnitude of 17.8 obtained at the 60cm f/8 Ganymed telescope located at Skinakas Observatory, Crete, Greece, using a ST10XME CCD Camera. The object is confirmed on CCD images with the same telescope using a broad H-alpha filter (4*120 s stacked, 17.7 mag) obtained on 2007 Aug 30.029.

We performed spectroscopy of four optical nova candidates in M31 using the Russian 6-m telescope and the SCORPIO spectrograph. The spectral range was 380-755 nm, and the spectral resolution was 1.34 nm. M31N 2007-07b (E. Ovcharov, et al., ATel#1139): The exposure was taken between 2007 July 19.925 and 19.957 UT about 10 days after the discovery. Balmer emission lines are dominant. The value of FWHM(Halpha) corrected for instrumental profile and EW(Halpha) are 1600 km/s and -71 nm, correspondingly.

The Author list was incomplete in ATel#1152. On 2007 July 21.46 UT a spectrum of the nova candidate M31N 2007-07c (see ATel#1146, ATel#1149) was obtained with Double-Beam Spectrograph on the Palomar Hale-5m telescope. The 400/6000 grism (3.5 angstrom FWHM) and 158/7500 grating (8.6 angstrom FWHM) were used with 1200s exposure, each. The H-alpha line displays a P-Cygni profile. The measured expansion velocity is -1630+/-20 km/ sec (blue shifted), based on measurements of the Ca H+K lines, the G Band, H-beta, Mg lines and the near-infrared Ca-triplet.

We report the discovery of an optical nova in M31 on four consecutive dithered R filter CCD images (each with 100 sec exposure) obtained on 2007 July 25.92564, 25.92714, 25.92865, 25.93015 with corresponding R magnitudes of 18.1, 18.2, 18.1, 18.1 obtained at the 1.3m f/7.5 telescope at Skinakas Observatory, Crete, Greece, using an Andor DZ436-BV CCD Camera. The position obtained for the nova candidate is RA(2000) = 00 42 43.29 , Dec(2000) = +41 17 44.10 with an accuracy of 0.2".

We report the discovery of an optical nova in M31 at RA(2000) = 00h 42m 59.49s , Dec(2000) = +41° 15' 06.5" with an accuracy of 0.2". The observations were obtained at the 1.3m Ritchey Chretien f/7.5 telescope at Skinakas Observatory, Crete, Greece, using an Andor DZ436-BV CCD Camera (with a Marconi 2k x 2k chip with 13.5µm sq. pixels). The observations were taken through a Johnson standard R filter (4*100 s stacked) and a broad H- alpha filter (3*300 s stacked).

We report the discovery of a optical nova in M31 on four consecutive dithered R filter CCD images obtained on (2007 July 19.00741, 19.00890, 19.01041, 19.01193, with corresponding R magnitudes of 18.8, 18.7, 18.8, 18.5) obtained at the 1.3m Ritchey Chretien f/7.5 telescope at Skinakas Observatory, Crete, Greece, using an Andor DZ436-BV CCD Camera (with a Marconi 2k x 2k chip with 13.5µm sq. pixels).

We report the discovery of a possible nova in M31 on four consecutive dithered R filter CCD images obtained on (2007 July 05.04813, 05.04966, 05.05122, 05.05278, with corresponding R magnitudes of 16.7, 16.6, 16.6, 16.6) obtained at the 1.3m Ritchey Chretien f/7.5 telescope at Skinakas Observatory, Crete, Greece, using the Roper CCD Camera (with a SITE 1k x 1k chip with 24µm sq. pixels). The position obtained for the nova candidate is RA(2000) = 00h 43m 04.05s, Dec(2000) = +41° 17' 08.3" with an accuracy of 0.1".

We discuss the results from the optical study of the X-ray sources detected in our Chandra survey of the central region of the Small Magellanic Cloud. Based on the OGLE-II and MCPS optical photometric catalogs we propose the most likely counterpart for 113 X-ray sources, 32 of which are identified with early type counterparts (of OB spectral type based on their position in color-magnitude diagrams). Optical spectroscopy of these counterparts with the 2dF spectrograph (AAT) reveals 13 new Be-XRBs in the SMC "bar". We estimate that these Be-XRBs have an age of 15-85 Myr, consistent with the typical age of Be stars. We also examine the "overabudance" of Be-XRBs in the SMC fields covered by Chandra, in comparison to the Milky Way, and we show that there is residual excess, even after accounting for the higher star formation rate of the SMC. This excess can be attributed to the lower metallicity of the SMC. Finally, we present a preliminary study of the parent stellar populations of these X-ray binaries based on deep IMACS observations. This work was supported by NASA LTSA grant NAG5-13056, and NASA grant G02-3117X.

We have studied the spatial and temporal variation of the surface longwave radiation (downwelling and net) over a 21-year period in the tropical and subtropical Pacific Ocean (40 S-40 N, 90 E-75 W). The fluxes were computed using a deterministic model for atmospheric radiation transfer, along with satellite data from the ISCCP-D2 database and reanalysis data from NCEP/NCAR (acronyms explained in main text), for the key atmospheric and surface input parameters. An excellent correlation was found between the downwelling longwave radiation (DLR) anomaly and the Ni&ntilde;o-3.4 index time-series, over the Ni&ntilde;o-3.4 region located in the central Pacific. A high anti-correlation was also found over the western Pacific (15-0 S, 105-130 E). There is convincing evidence that the time series of the mean downwelling longwave radiation anomaly in the western Pacific precedes that in the Ni&ntilde;o-3.4 region by 3-4 months. Thus, the downwelling longwave radiation anomaly is a complementary index to the SST anomaly for the study of ENSO events and can be used to asses whether or not El Ni&ntilde;o or La Ni&ntilde;a conditions prevail. Over the Ni&ntilde;o-3.4 region, the mean DLR anomaly values range from +20 Wm-2 during El Ni&ntilde;o episodes to -20 Wm-2 during La Ni&ntilde;a events, while over the western Pacific (15-0 S, 105-130 E) these values range from -15 Wm-2 to +10 Wm-2, respectively. The long- term average (1984-2004) distribution of the net downwelling longwave radiation at the surface over the tropical and subtropical Pacific for the three month period November-December-January shows a net thermal cooling of the ocean surface. When El Ni&ntilde;o conditions prevail, the thermal radiative cooling in the central and south-eastern tropical Pacific becomes weaker by 10 Wm-2 south of the equator in the central Pacific (7-0 S, 160-120 W) for the three-month period of NDJ, because the DLR increase is larger than the increase in surface thermal emission. In contrast, the thermal radiative cooling over Indonesia is enhanced by 10 Wm-2 during the early (August-September-October) El Ni&ntilde;o phase.

During the period 2004 to 2005, the following symposia and colloquia were related to the activities of the commission: The A-Star Puzzle (IAUS224), Massive Star Birth: A Crossroads of Astrophysics (IAUS227), and From Lithium to Uranium: Elemental Tracers of Early Cosmic Evolution (IAUS228).

The Commission business meeting was held on 17 August 2006. Approximately 20 people attended, including the Commission vice-president, Rainer Spurzem. The sole member of the Commission Organizing Committee that was present was Gary Da Costa, who, along with Patricia Whitelock, the outgoing president of Division VII and Commission 33, served as chairs of the meeting.

We report the discovery of an optical nova candidate in the outer disk of M 31 on nine stacked R filter images (each with 60 sec exposure) and four stacked 12nm H-alpha filter images (each with 120 sec exposure) on 2007 Aug 24.081 and 24.093 with a magnitude of 18.7 in R and 18.1 in H-alpha, respectively. The images were obtained at the 60cm f/3 Ganymed telescope located at Skinakas Observatory, Crete, Greece, using a STL11000M CCD Camera.

We report the discovery of a possible nova in M31 on four consecutive dithered stacked R filter CCD images, obtained on 2007 September 02.09, with the 1.3m Ritchey Chretien f/7.5 telescope at Skinakas Observatory, Crete, Greece, using an Andor DZ436-BV CCD Camera (with a Marconi 2k x 2k chip with 13.5µm sq. pixels). The R magnitude of the object was 18.1. On 2007 September 03.09, the object was again detected with the same instrument setup, with an R magnitude of 18.2.

In this study, we investigate the aerosol optical properties, namely aerosol extinction optical thickness (AOT), Angström parameter and size distribution over the Eastern Mediterranean Basin, using spectral measurements from the recently established FORTH (Foundation for Research and Technology-Hellas) AERONET station in Crete, for the two-year period 2003-2004. The location of the FORTH-AERONET station offers a unique opportunity to monitor aerosols from different sources. Maximum values of AOT are found primarily in spring, which together with small values of the Angström parameter indicate dust transported from African deserts, whereas the minimum values of AOT occur in winter. In autumn, large AOT values observed at near-infrared wavelengths arise also from dust transport. In summer, large AOT values at ultraviolet (340 nm) and visible wavelengths (500 nm), together with large values of the Angström parameter, are associated with transport of fine aerosols of urban/industrial and biomass burning origin. The Angström parameter values vary on a daily basis within the range 0.05-2.20, and on a monthly basis within the range 0.68-1.9. This behaviour, together with broad frequency distributions and back-trajectory analyses, indicates a great variety of aerosol types over the study region including dust, urban-industrial and biomass-burning pollution, and maritime, as well as mixed aerosol types. Large temporal variability is observed in AOT, Angström parameter, aerosol content and size. The fine and coarse aerosol modes persist throughout the year, with the coarse mode dominant except in summer. The highest values of AOT are related primarily to southeasterly winds, associated with coarse aerosols, and to a less extent to northwesterly winds associated with fine aerosols. The results of this study show that the FORTH AERONET station in Crete is well suited for studying the transport and mixing of different types of aerosols from a variety of sources, especially those associated with major dust events from the Sahara.

We report the discovery of a possible nova in M31 on an R filter CCD image (2006 September 17.03741, 17.1 mag) obtained at the 1.3m Ritchey Chretien f/7.5 Telescope at Skinakas Observatory, Crete, Greece using the Roper CCD Camera (with a SITE 1k x 1k chip with 24um sq. pixels). The position obtained for the nova candidate is RA(2000) = 00h 42m 41.45s, Dec(2000) = +41° 14' 44.55" with an accuracy of 0.11".

Context.Recent surveys of the Local Group spiral Galaxies M 31 and M 33 with XMM-Newton yielded a large number of X-ray sources. Aims.As part of the effort to identify and classify the objects responsible for this X-ray emission, we have obtained optical spectra of the brightest optical counterparts of the identified X-ray sources, using the 1.3 m Skinakas Telescope. Most of these objects are foreground star candidates. The purpose of the present study is to confirm this identification and to explore the compatibility between the optical spectral classification and the observed X-ray properties of the sources. Methods.We have obtained optical spectra for the 14 brightest optical counterparts of X-ray sources identified by XMM-Newton in the direction of M 31 and for 21 optical counterparts in the direction of M 33, using the 1.3 m Skinakas telescope in Crete, Greece. Results.All of the M 31 sources and all but one of the M 33 sources were confirmed to be foreground stars, of spectral types between A and M. One of the stars is a late M dwarf with Hα emission, a flare star, also displaying strong X-ray variability. One of the M 33 sources (lying within the D25 ellipse) corresponds to a previously known background galaxy, LEDA 5899.

In the present work a detailed seismotectonic study of the broader area of the Mygdonia basin (N. Greece) is performed. Digital data for earthquakes which occurred in the broader Mygdonia basin and were recorded by the permanent telemetric network of the Geophysical Laboratory of the Aristotle University of Thessaloniki during the period 1989-1999 were collected and fault plane solutions for 50 earthquakes which occurred in the study area were calculated with a modified first motions approach which incorporates amplitude and radiation pattern information. Fault plane solutions for the 3 main shocks of Volvi (23/05/78, MW = 5.8 and 20/06/78, MW = 6.5) and Arnaia (04/05/95, MW = 5.8) events and the 1978 aftershock sequence were additionally used. Moreover, data from two local networks established in the Mygdonia basin were also incorporated in the final dataset. Determination of the stress field was realized by the use of the method of Gephart and Forsyth [Gephart, J.W., Forsyth, D.W., 1984. An improved method for determining the regional stress tensor using earthquake focal mechanism data: application to the San Fernando earthquake sequence: Jour. Geophys. Res., v.89, no. B11, p. 9305-9320] for the stress tensor inversion and the results were compared with independent estimates based on the calculation of the average moment tensor [Papazachos, C.B.,Kiratzi, A.A., 1992. A formulation for reliable estimation of active crustal deformation and its application to central Greece. Geophys. J. Int. 111, 424-432]. The obtained stress results show a relatively good agreement between the two approaches, with differences in the azimuth of the dominant extension axis of the order of 10°. Furthermore, comparison with independent information for the mean stress axes provided by the study of kinematics on neotectonic faults [Mountrakis, D., Kilias, A., Tranos, M., Thomaidou, E., Papazachos, C., Karakaisis, G., Scordilis, E., Chatzidimitriou, P., Papadimitriou, E., Vargemezis, G., Aidona, E., Karagianni, E., Vamvakaris, D. Skarlatoudis, A. 2003. Determination of the settings and the seismotectonic behavior of the main seismic-active faults of Northern Greece area using neotectonic and seismological data. Earthquake Planning and Protection Organisation (OASP) (in Greek)] shows a similar agreement with typical misfit of the order 10°. The stress inversion method was modified in order to select one or both nodal planes of the focal mechanism which corresponds to the "true" fault plane of the occurred earthquakes and was able to select a single fault plane in the majority of examined cases. Using this approach, the obtained fault plane rose diagrams are in agreement with results from various neotectonic studies. Moreover, several secondary active fault branches were identified, which are still not clearly observed in the field.

The optical observations used in this study were carried out during three observing runs, on September 6, 2003, on October 18-22, 2003 and on October 10-11, 2004, using the 1.3-m Ritchey-Cretien telescope at Skinakas Observatory, located on the island of Crete (Greece). (3 data files).

We present an analysis of the individual observations of a deep XMM-Newton survey of the Local Group spiral galaxy M 33. We detected a total of 350 sources with fluxes (in the 0.2-4.5 keV energy band) in the range 6.7 × 10-16-1.5 × 10-11 erg s-1. This comprehensive study considers flux variability, spectral characteristics, and classification of the detected objects. Thirty-nine objects in our catalogue are new sources, while 311 were already detected in a previous analysis of most of the same data using combined images. We present improved positions of these sources and the X-ray parameters of each source in each individual observation that covers the source. We then used these parameters to systematically search for flux variability on time scales of hours to months or years. The long-term light-curves were generated for the 61 sources showing a significant variability of the (0.2-4.5) keV flux, by a factor of 1.2 to 144. The detected variability was then used to classify 8 new X-ray binary candidates in M 33. Together with the hardness ratio method and cross-correlation with optical, infrared, and radio data, we also classify or confirm previous classification of 25 supernova remnants and candidates, 2 X-ray binaries, and 11 super-soft source candidates (7 of which are new SSS candidates). In addition, we classify 13 active galactic nuclei and background galaxies, 6 stars, and 23 foreground star candidates in the direction of M 33. Further 206 objects are classified as "hard", approximately half of which are sources intrinsic to M 33. The relative contribution of the classified XRB and SSS in M 33 is now comparable to M 31. The luminosity distribution of SNRs in both spiral galaxies is almost the same, although the number of the detected SNRs in M 33 remains much higher.

Using 24 overlapping XMM-Newton observations of the Local Group spiral galaxy M 33, we have detected 447 sources in each individual pointing and in deep combined images. A total of 61 sources exhibit significant flux variations by a factor of up to 144, on time scales of hours to months or years. The detected variability, together with the hardness ratio (HR) method and optical identification (when available), is used to classify the sources as X-ray binaries (XRBs), supernova remnants (SNRs) and super-soft sources (SSS) in M 33, as well as background AGN and foreground stars in the field of view. The majority of sources can only be classified as ‘hard’, according to their HRs. We find that the luminosity distribution of the detected SNRs and SNR candidates in M 33 is similar to M 31, and slightly steeper than that of the LMC.

As shown in our first poster, in a recent survey of M33 with XMM-Newton we detected the X-ray source population of this nearby spiral galaxy down to the (0.2-4.5) keV luminosity of 1035 erg s-1, a factor of 10 deeper than in previous observations. The majority of the detected sources was classified using, in many cases, only their X-ray properties. In particular, 8 new X-ray binary (XRB) candidates were selected, based on their long-term X-ray light curves. We also classified supernova remnants (SNRs), super-soft sources (SSS), AGN, foreground stars and a population of ‘hard’ sources using the hardness ratio (HR) method. A detailed spectral and timing analysis of the brightest sources is in progress. We present a few examples of spectra for particular source classes. We find that bright ‘hard’ sources can be divided into two broad families: one best modelled by a powerlaw with photon index in the range of 1.0-2.0, and the other displaying disk blackbody spectra with kT of 0.8 to 1.5 keV.

We calculate the monthly components of the Mediterranean Sea heat budget, namely the net shortwave, net longwave, latent, sensible heat fluxes, and heat storage change, for years 1984-2000. The radiative components of the seasonal heat budget are derived by a radiation transfer model, while in most other studies bulk formulae are used. A variety of data are required to run the model, among which are cloud data from International Satellite Cloud Climatology Project (ISCCP) D2 data set, aerosol data from Global Aerosol Data Set (GADS), temperature and humidity from National Center for Environmental Prediction/National Center for Atmospheric Research (NCEP/NCAR) and European Centre for Medium-range Weather Forecasts (ECMWF) Re-Analysis (ERA-40), and oceanographical data from Mediterranean Data Archaeology and Rescue (MEDAR) MEDATLAS database and the World Ocean Atlas 2001. We compare two methods for the estimation of the monthly latent heat flux and evaporation: the bulk aerodynamic and the heat balance. The average annual evaporation rate for the Mediterranean Sea, based on the heat balance method, is estimated at 1500 ± 190 mm yr-1. The bulk aerodynamic method produces estimates of the annual evaporation rate in the range 1060-1280 mm yr-1, depending on the source of the input data. The analysis of the heat content shows that the solar heat absorbed by the sea during summer is redistributed to winter evaporation via heat storage by the sea. Thus the peak evaporation occurs in winter and is mainly driven by energy released (100-150 Wm-2) from sea heat storage.

The monthly mean shortwave (SW) radiation budget at the Earth's surface (SRB) was computed on 2.5-degree longitude-latitude resolution for the 17-year period from 1984 to 2000, using a radiative transfer model accounting for the key physical parameters that determine the surface SRB, and long-term climatological data from the International Satellite Cloud Climatology Project (ISCCP-D2). The model input data were supplemented by data from the National Centers for Environmental Prediction - National Center for Atmospheric Research (NCEP-NCAR) and European Center for Medium Range Weather Forecasts (ECMWF) Global Reanalysis projects, and other global data bases such as TIROS Operational Vertical Sounder (TOVS) and Global Aerosol Data Set (GADS). The model surface radiative fluxes were validated against surface measurements from 22 stations of the Baseline Surface Radiation Network (BSRN) covering the years 1992-2000, and from 700 stations of the Global Energy Balance Archive (GEBA), covering the period 1984-2000. The model is in good agreement with BSRN and GEBA, with a negative bias of 14 and 6.5 Wm-2, respectively. The model is able to reproduce interesting features of the seasonal and geographical variation of the surface SW fluxes at global scale. Based on the 17-year average model results, the global mean SW downward surface radiation (DSR) is equal to 171.6 Wm-2, whereas the net downward (or absorbed) surface SW radiation is equal to 149.4 Wm-2, values that correspond to 50.2 and 43.7% of the incoming SW radiation at the top of the Earth's atmosphere. These values involve a long-term surface albedo equal to 12.9%. Significant increasing trends in DSR and net DSR fluxes were found, equal to 4.1 and 3.7 Wm-2, respectively, over the 1984-2000 period (equivalent to 2.4 and 2.2 Wm-2 per decade), indicating an increasing surface solar radiative heating. This surface SW radiative heating is primarily attributed to clouds, especially low-level, and secondarily to other parameters such as total precipitable water. The surface solar heating occurs mainly in the period starting from the early 1990s, in contrast to decreasing trend in DSR through the late 1980s. The computed global mean DSR and net DSR flux anomalies were found to range within ±8 and ±6 Wm-2, respectively, with signals from El Niño and La Niña events, and the Pinatubo eruption, whereas significant positive anomalies have occurred in the period 1992-2000.

We present analysis of all 24 archival raster XMM-Newton (Jansen et al., 2001A&A...365L...1J) observations of M33. (2 data files).

We carried out spectroscopic observations of the optical transient near M31 reported in ATel #611 (RA = 00h38m54.63s DEC =+40o27'34.2" (J2000)) from the 1.3m telescope of the Skinakas Observatory in Crete (Greece) on the nights 28 and 29 September 2005. The spectra covered the range 3800-7000 angstroms. All the lines of the Balmer series up to H-8 appeared strongly in emission. The equivalent widths of the H-alpha and H-beta lines (the strongest emission features) on 28 September 2005 were -550+-25 angstrom and -220+-20 angstrom, respectively and the FWHM 1800+-30 km/s in both lines.

Titan's vertical atmospheric temperature profile, atmospheric chemical composition and haze structure are controlled by many processes. In this work we present a self-consistent 1D simulation of radiation transfer, photochemistry and haze microphysics that determine Titan's atmosphere and haze. The atmospheric model extends from the surface up to the lower thermosphere and incorporates: high resolution radiation transfer codes for solar and thermal radiation, complete neutral species photochemical evolution and a detailed Eulerian description of the microphysical haze particle growth. Chemical analysis of the laboratory produced haze analogs, suggests that the most probable photochemical pathways leading to haze formation, include copolymers of acetylene, hydrogen cyanide, aromatics and others. Although these pathways produce a Haze monomers mass production rate of the correct magnitude to fit the geometric albedo, their production profiles are significantly different from the simplified ones used in previous simulations. The photochemical part of the model produces the vertical profile of all the important hydrocarbons and nitriles in Titan's atmosphere including the polymerisation of organic species for Haze production. This interaction of the Haze precursors with the chemistry is considered to take place until the precursors reach a typical mass of ∼1000 amu, after which the polymers chemical growth ceases and the conglomeration of the Haze particles commences. The resulting distribution of different size particles, along with the rest of the species interacting with the radiation field are included in the radiative/convective part of the model for the calculation of the thermal structure. The model iterates between these processes until a steady state is reached. The results presented are validated against observed data (geometric albedo, chemical composition, thermal structure, etc.) in order to understand better the physical processes that control: Titan's methane abundance; the production, structure and radiative properties of the haze; and the radiative properties of Titan's atmosphere and surface.

A decadal-scale trend in the tropical radiative energy budget has been observed recently by satellites, which however is not reproduced by climate models. In the present study, we have computed the outgoing shortwave radiation (OSR) at the top of atmosphere (TOA) at 2.5° longitude-latitude resolution and on a mean monthly basis for the 17-year period 1984-2000, by using a deterministic solar radiative transfer model and cloud climatological data from the International Satellite Cloud Climatology Project (ISCCP) D2 database. Anomaly time series for the mean monthly pixel-level OSR fluxes, as well as for the key physical parameters, were constructed. A significant decreasing trend in OSR anomalies, starting mainly from the late 1980s, was found in tropical and subtropical regions (30° S-30° N), indicating a decadal increase in solar planetary heating equal to 1.9±0.3Wm-2/decade, reproducing well the features recorded by satellite observations, in contrast to climate model results. This increase in solar planetary heating, however, is accompanied by a similar increase in planetary cooling, due to increased outgoing longwave radiation, so that there is no change in net radiation. The model computed OSR trend is in good agreement with the corresponding linear decadal decrease of 2.5±0.4Wm-2/decade in tropical mean OSR anomalies derived from ERBE S-10N non-scanner data (edition 2). An attempt was made to identify the physical processes responsible for the decreasing trend in tropical mean OSR. A detailed correlation analysis using pixel-level anomalies of model computed OSR flux and ISCCP cloud cover over the entire tropical and subtropical region (30° S-30° N), gave a correlation coefficient of 0.79, indicating that decreasing cloud cover is the main reason for the tropical OSR trend. According to the ISCCP-D2 data derived from the combined visible/infrared (VIS/IR) analysis, the tropical cloud cover has decreased by 6.6±0.2% per decade, in relative terms. A detailed analysis of the inter-annual and long-term variability of the various parameters determining the OSR at TOA, has shown that the most important contribution to the observed OSR trend comes from a decrease in low-level cloud cover over the period 1984-2000, followed by decreases in middle and high-level cloud cover. Note, however, that there still remain some uncertainties associated with the existence and magnitude of trends in ISCCP-D2 cloud amounts. Opposite but small trends are introduced by increases in cloud scattering optical depth of low and middle clouds.

There are 509 expanding neutral hydrogen shells catalogued in the Small Magellanic Cloud (SMC), all apparently very young, with dynamical ages of a few Myr. To examine their relationship with young stellar objects, we cross-correlated the shell catalogue with various catalogues of OB associations, supergiants, Cepheids, Wolf-Rayet stars, supernova remnants and star clusters. The incidence of chance line-ups was estimated via Monte Carlo simulations, and found to be high. However, it is important that there are 1.5 times more shells that are not spatially correlated to an OB association, than shells that are. Moreover, 59 of the 509 shells lie mainly in low stellar density fields and have no young stellar objects associated with them, and therefore no obvious energy source. It is shown that, on the whole, the properties of these `empty' shells are very similar to the properties of the rest of the shells, once selection biases are taken into account. In both cases, the shell radius and expansion velocity distribution functions are consistent with the standard model, according to which shells are created by stellar winds and supernova explosions, as long as all shells were created in a single burst and with a power-law distribution of the input mechanical luminosity. This would indicate a burst of star formation. This interpretation, however, cannot explain why the 59 shells, with no young stellar counterparts, show almost exactly the same behaviour as shells with OB associations within their radius. Gamma-ray bursts could account for some but certainly not for the majority of the `empty' shells. Many `empty' shells, including most of the high-luminosity ones, are located in the north-western outer regions of the SMC, and may be associated with a chimney-like feature that is known to exist in that area. Finally, it is noted that turbulence is a promising mechanism for the formation of the shell-like structures, but direct comparison with the observations was not possible at this stage, due to lack of detailed models.

From a sample of 304 carbon stars in the central parts of the Large Magellanic Cloud (LMC), ~27 per cent have Merrill-Sanford (MS) bands of the SiC2 molecule. The data are based on a uniform set of spectra taken with 2dF on the Anglo-Australian Telescope, and give useful statistics on the incidence of MS bands and on their correlation (or otherwise) with other properties. All of these are red stars, cooler than 3100 K. The proportion of stars showing the bands is highest amongst the coolest stars, but not all very cool stars show the bands. There is no evidence that MS bands are more common in J-type stars (carbon stars with a high 13C/12C ratio) than in N-type carbon stars, at least within this sample of LMC stars. There is no apparent correlation with stellar variability, or between the photospheric temperature [as measured by (J-K)] and the occurrence of the 'hot' MS bands from excited molecular states. (2 data files).

1. Resonances and stability of extra-solar planetary systems C. Beaugé, N. Callegari, S. Ferraz-Mello and T. A. Michtchenko; 2. Formation, migration, and stability of extrasolar planetary systems Fred C. Adams; 3. Dynamical evolution of extrasolar planetary systems Ji-Lin Zhou and Yi-Sui Sun; 4. Dynamics of planetesimals: the role of two-body relaxation Eiichiro Kokubo; 5. Fitting orbits Andrzej J. Maciejewski, Krzysztof Gozdziewski and Szymon Kozlowski; 6. The secular planetary three body problem revisited Jacques Henrard and Anne-Sophie Libert; 7. Dynamics of extrasolar systems at the 5/2 resonance: application to 47 UMa Dionyssia Psychoyos and John D. Hadjidemetriou; 8. Our solar system as model for exosolar planetary systems Rudolf Dvorak, Áron Süli and Florian Freistetter; 9. Planetary motion in double stars: the influence of the secondary Elke Pilat-Lohinger; 10. Planetary orbits in double stars: influence of the binary's orbital eccentricity Daniel Benest and Robert Gonczi; 11. Astrometric observations of 51 Peg and Gliese 623 at Pulkovo observatory with 65 cm refractor N. A. Shakht; 12. Observations of 61 Cyg at Pulkovo Denis L. Gorshanov, N. A. Shakht, A. A. Kisselev and E. V. Poliakow; 13. Formation of the solar system by instability Evgeny Griv and Michael Gedalin; 14. Behaviour of a two-planetary system on a cosmogonic time-scale Konstantin V. Kholshevnikov and Eduard D. Kuznetsov; 15. Boundaries of the habitable zone: unifying dynamics, astrophysics, and astrobiology Milan M. Cirkovic; 16. Asteroid proper elements: recent computational progress Fernando Roig and Cristian Beaugé; 17. Asteroid family classification from very large catalogues Anne Lemaitre; 18. Non-gravitational perturbations and evolution of the asteroid main belt David Vokrouhlicky, M. Broz and W. F. Bottke, D. Nesvorny and A. Morbidelli; 19. Diffusion in the asteroid belt Harry Varvoglis; 20. Accurate model for the Yarkovsky effect David Capek and David Vokrouhlicky; 21. The population of asteroids in the 2:1 mean motion resonance with Jupiter revised Miroslav Broz, D. Vokrouhlicky, F. Roig, D. Nesvorny, W. F. Bottke and A. Morbidelli; 22. On the reliability of computation of maximum Lyapunov Characteristic Exponents for asteroids Zoran Knezevic and Slobodan Ninkovic; 23. Nekhoroshev stability estimates for different models of the Trojan asteroids Christos Efthymiopoulos; 24. The role of the resonant 'stickiness' in the dynamical evolution of Jupiter family comets A. Alvarez-Canda and F. Roig; 25. Regimes of stability and scaling relations for the removal time in the asteroid belt: a simple kinetic model and numerical tests Mihailo Cubrovic; 26. Virtual asteroids and virtual impactors Andrea Milani; 27. Asteroid population models Alessandro Morbidelli; 28. Linking Very Large Telescope asteroid observations M. Granvik, K. Muinonen, J. Virtanen, M. Delbó, L. Saba, G. De Sanctis, R. Morbidelli, A. Cellino and E. Tedesco; 29. Collision orbits and phase transition for 2004 AS1 at discovery Jenni Virtanen, K. Muinonen, M. Granvik and T. Laakso; 30. The size of collision solutions in orbital elements space G. B. Valsecchi, A. Rossi, A. Milani and S. R. Chesley; 31. Very short arc orbit determination: the case of asteroid 2004 FU162 Steven R. Chesley; 32. Nonlinear impact monitoring: 2-dimensional sampling Giacomo Tommei; 33. Searching for gravity assisted trajectories to accessible near-Earth asteroids Stefan Berinde; 34. KLENOT - Near Earth and other unusual objects observations Michal Kocer, Jana Tichá and M. Tichy; 35. Transport of comets to the Inner Solar System Hans Rickman; 36. Nongravitational Accelerations on Comets Steven R. Chesley and Donald K. Yeomans; 37. Interaction of planetesimals with the giant planets and the shaping of the trans-Neptunian belt Harold F. Levison and Alessandro Morbidelli; 38. Transport of comets to the outer p

Downwelling longwave fluxes, DLFs, have been derived for each month over a ten year period (1984-1993), on a global scale with a spatial resolution of 2.5x2.5 degrees and a monthly temporal resolution. The fluxes were computed using a deterministic model for atmospheric radiation transfer, along with satellite and reanalysis data for the key atmospheric input parameters, i.e. cloud properties, and specific humidity and temperature profiles. The cloud climatologies were taken from the latest released and improved International Satellite Climatology Project D2 series. Specific humidity and temperature vertical profiles were taken from three different reanalysis datasets; NCEP/NCAR, GEOS, and ECMWF (acronyms explained in main text). DLFs were computed for each reanalysis dataset, with differences reaching values as high as 30 Wm-2 in specific regions, particularly over high altitude areas and deserts. However, globally, the agreement is good, with the rms of the difference between the DLFs derived from the different reanalysis datasets ranging from 5 to 7 Wm-2. The results are presented as geographical distributions and as time series of hemispheric and global averages. The DLF time series based on the different reanalysis datasets show similar seasonal and inter-annual variations, and similar anomalies related to the 86/87 El Niño and 89/90 La Niña events. The global ten-year average of the DLF was found to be between 342.2 Wm-2 and 344.3 Wm-2, depending on the dataset. We also conducted a detailed sensitivity analysis of the calculated DLFs to the key input data. Plots are given that can be used to obtain a quick assessment of the sensitivity of the DLF to each of the three key climatic quantities, for specific climatic conditions corresponding to different regions of the globe. Our model downwelling fluxes are validated against available data from ground-based stations distributed over the globe, as given by the Baseline Surface Radiation Network. There is a negative bias of the model fluxes when compared against BSRN fluxes, ranging from -7 to -9 Wm-2, mostly caused by low cloud amount differences between the station and satellite measurements, particularly in cold climates. Finally, we compare our model results with those of other deterministic models and general circulation models.

From a sample of 304 carbon stars in the central parts of the Large Magellanic Cloud (LMC), ~27 per cent have Merrill-Sanford (MS) bands of the SiC2 molecule. The data are based on a uniform set of spectra taken with 2dF on the Anglo-Australian Telescope, and give useful statistics on the incidence of MS bands and on their correlation (or otherwise) with other properties. All of these are red stars, cooler than 3100 K. The proportion of stars showing the bands is highest amongst the coolest stars, but not all very cool stars show the bands. There is no evidence that MS bands are more common in J-type stars (carbon stars with a high 13C/12C ratio) than in N-type carbon stars, at least within this sample of LMC stars. There is no apparent correlation with stellar variability, or between the photospheric temperature [as measured by (J-K)] and the occurrence of the `hot' MS bands from excited molecular states.

A 10 year (1984-93) climatology is given of the global distributions of net shortwave (SW), net longwave (LW) and net all-wave radiation budget at both top-of-atmosphere (TOA) and at the Earth's surface, on a mean monthly basis, computed with a radiative transfer model with input data for key atmospheric and surface parameters. The model input data were taken from complete and comprehensive global climatological data sets, such as the International Satellite Cloud Climatology Project, the National Centers for Environmental Prediction and National Center for Atmospheric Research Global Reanalysis or the TIROS Operational Vertical Sounder, among others. Seasonal and latitudinal variations and mean annual and mean hemispherical and global averages are given, based on model results computed for each month of the period from January 1984 to December 1993. At TOA, the net incoming SW radiation has larger latitudinal variation and range of values (0-400 W m-2) than the outgoing LW radiation (100-350 W m-2). At the surface, the net downward SW radiation has similar features to that at TOA, but with smaller magnitudes. The net upward LW radiation is quite different than at TOA, with a smaller seasonal and geographical variability than the surface net SW radiation. The global system of Earth-atmosphere is found to be net radiatively heated at TOA by 3 W m-2; the Earth's surface is net heated by 98 W m-2, mainly due to solar absorption equal to 147 W m-2, a value in agreement with surface-based measurements. At TOA, there is a radiative energy surplus between 40 °S and 30 °N and a radiative loss poleward; however, at the surface the surplus regions extend from 70 °S to 70 °N. Globally, the atmosphere is found to absorb 27% of the incoming solar radiation at TOA, while it emits 79% of the outgoing terrestrial radiation.

In an XMM-Newton raster observation of the bright Local Group spiral galaxy M 33 we study the population of X-ray sources (X-ray binaries, supernova remnants) down to a 0.2-4.5 keV luminosity of 1035 erg s-1 - more than a factor of 10 deeper than earlier ROSAT observations. EPIC hardness ratios and optical and radio information are used to distinguish between different source classes. The survey detects 408 sources in an area of 0.80 square degree. We correlate these newly detected sources with earlier M 33 X-ray catalogues and information from optical, infra-red and radio wavelengths. As M 33 sources we detect 21 supernova remnants (SNR) and 23 SNR candidates, 5 super-soft sources and 2 X-ray binaries (XRBs). There are 267 sources classified as hard, which may either be XRBs or Crab-like SNRs in M 33 or background AGN. The 44 confirmed and candidate SNRs more than double the number of X-ray detected SNRs in M 33. 16 of these are proposed as SNR candidates from the X-ray data for the first time. On the other hand, there are several sources not connected to M 33: five foreground stars, 30 foreground star candidates, 12 active galactic nucleus candidates, one background galaxy and one background galaxy candidate. Extrapolating from deep field observations we would expect 175 to 210 background sources in this field. This indicates that about half of the sources detected are within M 33. XMM-Newton is an ESA Science Mission with instruments and contributions directly funded by ESA Member States and the USA (NASA). Full Table \ref{master} is only available in electronic form at the CDS via anonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5) or via http://cdsweb.u-strasbg.fr/cgi-bin/qcat?J/A+A/426/11

In the present paper, we have calculated the outgoing longwave radiation at the top of the atmosphere (OLR at TOA) using a deterministic radiation transfer model, cloud data from ISCCP-D, and atmospheric temperature and humidity data from NCEP/NCAR reanalysis, for the seventeen-year period 1984-2000. We constructed anomaly time-series of the OLR at TOA, as well as of all of the key input climatological data, averaged in the tropical region between 20°N and 20°S. We compared the anomaly time-series of the model calculated OLR at TOA with that obtained from the ERBE S-10N (WFOV NF edition 2) non-scanner measurements. The model results display very similar seasonal and inter-annual variability as the ERBS data, and indicate a decadal increase of OLR at TOA of 1.9±0.2Wm-2/decade, which is lower than that displayed by the ERBS time-series (3.5±0.3Wm-2). Analysis of the inter-annual and long-term variability of the various parameters determining the OLR at TOA, showed that the most important contribution to the observed trend comes from a decrease in high-level cloud cover over the period 1984-2000, followed by an apparent drying of the upper troposphere and a decrease in low-level cloudiness. Opposite but small trends are introduced by a decrease in low-level cloud top pressure, an apparent cooling of the lower stratosphere (at the 50mbar level) and a small decadal increase in mid-level cloud cover.

The mean monthly shortwave (SW) radiation budget at the top of atmosphere (TOA) was computed on 2.5° longitude-latitude resolution for the 14-year period from 1984 to 1997, using a radiative transfer model with long-term climatological data from the International Satellite Cloud Climatology Project (ISCCP-D2) supplemented by data from the National Centers for Environmental Prediction - National Center for Atmospheric Research (NCEP-NCAR) Global Reanalysis project, and other global data bases such as TIROS Operational Vertical Sounder (TOVS) and Global Aerosol Data Set (GADS). The model radiative fluxes at TOA were validated against Earth Radiation Budget Experiment (ERBE) S4 scanner satellite data (1985-1989). The model is able to predict the seasonal and geographical variation of SW TOA fluxes. On a mean annual and global basis, the model is in very good agreement with ERBE, overestimating the outgoing SW radiation at TOA (OSR) by 0.93 Wm-2 (or by 0.92%), within the ERBE uncertainties. At pixel level, the OSR differences between model and ERBE are mostly within ±10 Wm-2, with ±5 Wm-2 over extended regions, while there exist some geographic areas with differences of up to 40 Wm-2, associated with uncertainties in cloud properties and surface albedo. The 14-year average model results give a planetary albedo equal to 29.6% and a TOA OSR flux of 101.2 Wm-2. A significant linearly decreasing trend in OSR and planetary albedo was found, equal to 2.3 Wm-2 and 0.6% (in absolute values), respectively, over the 14-year period (from January 1984 to December 1997), indicating an increasing solar planetary warming. This planetary SW radiative heating occurs in the tropical and sub-tropical areas (20° S-20° N), with clouds being the most likely cause. The computed global mean OSR anomaly ranges within ±4 Wm-2, with signals from El Niño and La Niña events or Pinatubo eruption, whereas significant negative OSR anomalies, starting from year 1992, are also detected.

In an XMM-Newton raster observation of the bright Local Group spiral galaxy M 33 we study the population of X-ray sources (X-ray binaries, supernova remnants) down to a 0.2-4.5keV luminosity of 1035erg/s - more than a factor of 10 deeper than earlier ROSAT observations. EPIC hardness ratios and optical and radio information are used to distinguish between different source classes. The survey detects 408 sources in an area of 0.80 square degree. We correlate these newly detected sources with earlier M 33 X-ray catalogues and information from optical, infra-red and radio wavelengths. As M 33 sources we detect 21 supernova remnants (SNR) and 23 SNR candidates, 5 super-soft sources and 2 X-ray binaries (XRBs). There are 267 sources classified as hard, which may either be XRBs or Crab-like SNRs in M 33 or background AGN. The 44 confirmed and candidate SNRs more than double the number of X-ray detected SNRs in M 33. 16 of these are proposed as SNR candidates from the X-ray data for the first time. On the other hand, there are several sources not connected to M 33: five foreground stars, 30 foreground star candidates, 12 active galactic nucleus candidates, one background galaxy and one background galaxy candidate. Extrapolating from deep field observations we would expect 175 to 210 background sources in this field. This indicates that about half of the sources detected are within M 33. (1 data file).

We present B, V, R and I photometry for NGC 6779 (M56), a metal-poor globular cluster in the galactic halo. The observations were performed using the 1.3-m telescope at Skinakas Observatory, in Crete. The reddening of the cluster was found to be E(B-V) = 0.32 ± 0.02 [E(V-I) = 0.43 ± 0.02], significantly higher than previous estimates. The metal abundance of the cluster was derived from various parametrizations of red giant branch characteristics and it was found to be [Fe/H]ZW=-2.20 ± 0.12 dex on the Zinn-West metallicity scale, or [Fe/H]CG=-2.00 ± 0.21 dex on the Carretta-Gratton scale. The distance modulus of the cluster is estimated to be (m-M)V= 15.62 ± 0.26 (or 14.62, if we correct for the reddening to the cluster). The horizontal branch of NGC 6779 shows a clear gap at (B-V)o= 0.0. Finally, the revised value for the metallicity of NGC 6779 led to a revision of its age to 13 Gyr, using the age-index calibrations of Salaris & Weiss.

We present a study of bright X-ray sources in the central part of the Small Magellanic Cloud based on a survey performed with the Chandra X-ray Observatory (see accompanying poster by J. McDowell et al). From the 122 sources (at the 3σ level), detected within the 1280 arcmin2 covered by the survey, we concentrate on the 16 brightest sources (>100 counts; LX > 1035erg/s) for which we can perform detailed spectral and timing analysis. These sources include two known supernova remnants (in one of which we identify a weak central point-like source), seven known X-ray binaries, and five previously detected sources which are most likely pulsar binaries, based on spectra and variability from the Chandra data. Two sources were not detected by any previous scans and are new transient candidate X-ray binary pulsars. This work was supported in part by the SAO intern program under NSF grant AST-9731923 and in part by NASA Grant G02-3117X.

We summarize the early results from a Chandra X-ray Observatory survey of the central region of the Small Magellanic Cloud, dominated by a recent burst of star formation. We detect 122 sources in five ACIS fields, reaching a 0.1-10 keV luminosity (corrected for Milky Way absorption ) of 4.3× 1033 erg/s, an order of magnitude deeper than previous surveys. Our survey includes 20 candidate transient sources and measures extent in 5 supernova remnants. The data indicate fewer very faint sources than would be expected from the background. We compare our results with ROSAT and ASCA observations of the region; many of the ASCA sources are found to suffer from confusion. We are beginning a program of optical identifications for the newly discovered sources. The companion poster by Taylor et al. describes our X-ray spectral and timing analysis on the bright sources. We acknowledge support from the Chandra X-ray Center (NASA contract NAS8-39073).

Six stars out of a sample of ~2300 carbon stars in the Magellanic Clouds have been identified as having strong C2 bands but CN bands that are very weak or absent. It is argued that five of these are likely to be R Coronae Borealis (RCB) stars on the basis of their spectral characteristics and peculiar colours. Most are variables and the Large Magellanic Cloud (LMC) members have extreme radial velocities that are more like the planetary nebula population than the carbon stars. This sample consists of four LMC members (only one of them previously recognized as an RCB star), one Small Magellanic Cloud (SMC) member (the first RCB star reported in the SMC) and one foreground Galactic star.

19 carbon stars that show lithium enrichment in their atmospheres have been discovered among a sample of 674 carbon stars in the Large Magellanic Cloud. Six of the Li-rich carbon stars are of the J type, i.e. they show strong 13C isotopic features. No super-Li-rich carbon stars were found. The incidence of lithium enrichment among carbon stars in the LMC is much rarer than in the Galaxy, and about five times more frequent among J-type than among N-type carbon stars. The bolometric magnitudes of the Li-rich carbon stars range between -3.3 and -5.7. Existing models of Li-enrichment via the hot bottom burning process fail to account for all of the observed properties of the Li-enriched stars studied here.

Most of the carbon stars observed with 2dF were selected from the newly completed catalogue of 7760 carbon stars by (Kontizas et al., 2001, Cat. , hereafter KDMK01). (1 data file).

We present preliminary results from our Cycle 3 Chandra survey of the central region of the Small Magellanic Cloud. Five ACIS-I fields cover a large fraction of the bar. The images show at least ten bright, extended, supernova remnants and two bright, previously unknown, transients; point sources are detected down to a luminosity of log L(erg/s) = 33. We have obtained exposure-corrected luminosity functions for each field.

A sample of 1497 carbon stars in the Large Magellanic Cloud (LMC) has been observed in the red part of the spectrum with the 2dF facility on the Anglo-Australian Telescope. Of these, 156 have been identified as J-type (i.e. 13C-rich) carbon stars using a technique which provides a clear distinction between J stars and the normal N-type carbon stars that comprise the bulk of the sample, and yields few borderline cases. A simple two-dimensional classification of the spectra, based on their spectral slopes in different wavelength regions, has been constructed and found to be related to the more conventional c and j indices, modified to suit the spectral regions observed. Most of the J stars form a photometric sequence in the K- (J-K) colour-magnitude diagram, parallel to and 0.6 mag fainter than the N-star sequence. A subset of the J stars (about 13 per cent) are brighter than this J-star sequence; most of these are spectroscopically different from the other J stars. The bright J stars have stronger CN bands than the other J stars and are found strongly concentrated in the central regions of the LMC. Most of the rather few stars in common with Hartwick and Cowley's sample of suspected CH stars are J stars. Overall, the proportion of carbon stars identified as J stars is somewhat lower than has been found in the Galaxy. The Na D lines are weaker in the LMC J stars than in either the Galactic J stars or the LMC N stars, and do not seem to depend on temperature.

We present BVRI CCD photometry for 12 RR Lyrae variables, including three newly discovered ones in the Oosterhoff type II globular cluster NGC 6426. New light curves and ephemerides are presented. The mean periods of the RRab and RRc variables whose light curves are analyzed in this work are <Pab>=0.70+/-0.02 days and <Pc>=0.34+/-0.03 days, respectively. The number ratio of the RRc type variables to the total number of RR Lyrae type variables is n(c)/n(ab+c)=0.36. The period-amplitude relation for fundamental-mode RR Lyrae variables (RRab) in NGC 6426 supports the recent conclusion of Clement & Shelton that this relation is not a function of metal abundance. Fourier decomposition of the light curves has been used to determine the mass, luminosity, and temperature for the RRc stars. Application of the formula of Jurcsik & Kovács, which relates Fourier parameters of RRab stars to [Fe/H], yielded the value [Fe/H]=-2.16+/-0.13 dex, which is compatible (given the errors) with the value -2.33+/-0.15 dex, derived from the red giant branch color index developed by Hatzidimitriou et al. From star counts along the horizontal branch (HB), we obtain the Lee et al. HB color distribution index, (B-R)/(B+V+R)=0.58+/-0.18. The HB of NGC 6426 resembles that of NGC 5053 and M68. We find almost no faint blue stars analogous to the ones constituting the extended HB in M15.

We report on the chemical abundances of stars in the Carina dwarf spheroidal galaxy (dSph) derived from low-resolution spectra. We have determined values of [Fe/H] for 52 stars from the reduced equivalent width of the Ca II infrared triplet lines. The Carina dSph has a mean metallicity of [Fe/H] = -1.99 +/- 0.08 and an intrinsic metallicity dispersion 0.25 dex (1 sigma). By directly determining the chemical abundances of Carina stars through spectroscopy, we can overcome the age-metallicity degeneracy inherent in color-magnitude diagrams (CMDs) and determine its star-formation history with unprecedented accuracy.

We present B, V, R, and I photometry of the metal-poor globular cluster in the galactic halo, NGC 6426. The observations were performed using the 1.3 m Telescope at Skinakas Observatory in Crete. We derived the reddening of the cluster to be E(B-V)=0.39+/-0.02 [E(V-I)=0.53+/-0.03]. The metal abundance of the cluster was estimated from the shape of the red giant branch following the techniques by Sarajedini and by Da Costa & Armandroff. It was found to be [Fe/H]=-2.33+/-0.15 dex. The mean V magnitude of the RR Lyrae variables found in the cluster is 18.14+/-0.02 (based on a paper in preparation). The resulting distance modulus of the cluster is 16.41+/-0.07. Finally, we derived the relative age of NGC 6426. Using the methodology of Harris et al., we found that NGC 6426 is marginally older than M92 (by ~=0.7 Gyr). Following the Chaboyer, Demarque, & Sarajedini method we found NGC 6426 to have the same age as the mean metal-poor globular cluster of the galactic halo.

We will describe recent results from the use of multi-object spectroscopy with the 2dF and Autofib systems on the AAT. Specific examples include a sample of 700 carbon stars in the LMC, for which kinematic, composition and classification data are being derived, and samples of stars in the Carina and Sculptor dwarf spheroidal galaxies. The future prospects for this type of work will be discussed.

The age and dynamics of the young LMC clusters SL 666 and NGC 2098 were investigated using CCD observations obtained with the 3.9m Anglo-Australian Telescope. SL 666 was found to have an age of 1 - 1.25 x 10(8) yr, while NGC 2098 is somewhat younger, with an age of 6.3 - 7.9*E(7) yr. In the case of SL 666 the good quality of the acquired data allowed the construction of the main sequence luminosity function as a function of radius, which revealed mass segregation, also confirmed from star counts. Since the age of SL 666 is significantly lower than the mean relaxation time of at least 5 x 10(8) yr calculated for this cluster and since the mass range of the cluster members does not permit us to assume faster energy equipartition, the observed mass segregation seems to be due to the way stars form in the cluster. Indications on a star formation scenario are examined. Disruption time is also discussed and there is strong evidence that the cluster is bound. NGC 2098 shows strong evidence of mass segregation, but further observations are needed in this case.

We have obtained spectra at the Ca ii triplet of individual red giants in seven Small Magellanic Cloud (SMC) star clusters whose ages range from ~4 to 12 Gyr. The spectra have been used to determine mean abundances for six of the star clusters to a typical precision of 0.12 dex. When combined with existing data for other objects, the resulting SMC age-metallicity relation is generally consistent with that for a simple model of chemical evolution, scaled to the present-day SMC mean abundance and gas mass fraction. Two of the clusters (Lindsay 113 and NGC 339), however, have abundances that are ~0.5 dex lower than that expected from the mean age-metallicity relation. It is suggested that the formation of these clusters, which have ages of ~5 Gyr, may have involved the infall of unenriched gas, perhaps from the Magellanic Stream. The spectra also yield radial velocities for the seven clusters. The resulting velocity dispersion is 16 +/- 4 km s^-1, consistent with those of the SMC planetary nebula and carbon star populations.

We present the results of a survey of neutral hydrogen emission in the Small Magellanic Cloud (SMC) with the Australia Telescope Compact Array (ATCA). The survey consists of a mosaic of 320 separate pointings of the 375-m array, resulting in a resolution of 1.6arcmin (28pc, for a distance of 60kpc) over a field of 20deg2. The rms brightness temperature sensitivity is 1.4K, corresponding to an H I column density sensitivity of 4x18cm-2 for each velocity channel of width 1.6km/s. The HI distribution is complex and, on scales <=1kpc, appears to be dominated by the effects of expanding H I shells, which are probably driven by the combined effects of supernovae and stellar winds from massive stars. The picture of the SMC that arises from the current data seems to challenge the earlier belief that the SMC consists of two or more spatially separate structures with different systemic velocities. We find that the observed multiple components are, in many cases, caused by the combined effects of the numerous shells and supershells. Altogether, we identify six supershells (defined here as those with radii greater than 300pc) and 495 giant shells. For each of these, we measure positions. radii, velocities and expansion rates, and derive ages and kinetic energy requirements. The apparent age distribution of shells is remarkably narrow, with a mean age of 5.4Myr and an intrinsic dispersion of 2Myr. Southern shells appear to be older, on average, by 2.5Myr. The kinetic energy of the shells is a large fraction of the gravitational binding energy of the SMC, implying that further disintegration of the SMC will occur with time, and especially at the next close passage with the Large Magellanic Cloud (LMC) or the Galaxy, unless the SMC possesses a massive halo. Because of their interferometric nature, the images presented here are insensitive to structures of size >=0.6°, and should not be used for deriving total H I column densities (1 data file).

We present the results of a survey of neutral hydrogen emission in the Small Magellanic Cloud (SMC) with the Australia Telescope Compact Array (ATCA). The survey consists of a mosaic of 320 separate pointings of the 375-m array, resulting in a resolution of 1.6 arcmin (28 pc, for a distance of 60 kpc) over a field of 20 deg^2. The rms brightness temperature sensitivity is 1.4 K, corresponding to an Hi column density sensitivity of 4x10^18 cm^-2 for each velocity channel of width 1.6kms^-1. The Hi distribution is complex and, on scales <~1 kpc, appears to be dominated by the effects of expanding Hi shells, which are probably driven by the combined effects of supernovae and stellar winds from massive stars. The picture of the SMC that arises from the current data seems to challenge the earlier belief that the SMC consists of two or more spatially separate structures with different systemic velocities. We find that the observed multiple components are, in many cases, caused by the combined effects of the numerous shells and supershells. Altogether, we identify six supershells (defined here as those with radii greater than 300 pc) and 495 giant shells. For each of these, we measure positions, radii, velocities and expansion rates, and derive ages and kinetic energy requirements. The apparent age distribution of shells is remarkably narrow, with a mean age of 5.4Myr and an intrinsic dispersion of 2Myr. Southern shells appear to be older, on average, by 2.5Myr. The kinetic energy of the shells is a large fraction of the gravitational binding energy of the SMC, implying that further disintegration of the SMC will occur with time, and especially at the next close passage with the Large Magellanic Cloud (LMC) or the Galaxy, unless the SMC possesses a massive halo. Because of their interferometric nature, the images presented here are insensitive to structures of size >~0 deg.6, and should not be used for deriving total Hi column densities.

We present a radial velocity survey of a sample of the field population of carbon stars in the outer parts of the Small Magellanic Cloud (SMC). This first set of results includes radial velocities for 71 carbon stars, with an individual precision of +/- 2-5 km/s. The mean heliocentric velocity of the stars (excluding one very high velocity star) is 149.3+/-3.0 km/s with a velocity dispersion of 25.2 +/- 2.1 km/s. These values drop to 145.5+/-2.7 km/s and 20.6+/-1.9 km/s respectively, if we exclude the stars belonging to the Outer Wing. The velocity distribution does not show the multiple peaks seen in some samples of Population I objects. The mass of the SMC as inferred from the above velocity dispersion (without the outer Wing stars) is ~= 1.2~10^9M_{\odot}. Tables 1a and 1b are available in electronic form at the CDS via anonymous ftp 130.79.128.5 or http://cdsweb.u-strasbg.fr/abstract.html

Irregular galaxies are generally less massive and less evolved systems than spirals. They constitute a different sort of system in which to study the processes of star formation and galactic evolution. The star formation history of Irregular Galaxies may be affected by several different factors. However, detailed knowledge of the star-formation history of a significant number of objects is necessary before it becomes possible to determine which parameters are important. In the last few years, there has been significant progress on this front. For the first time, we begin to probe in some detail the star-formation history of a fair number of resolved Irregulars in the Local Group. In the present, these results are summarized.

Spectra of 480 blue horizontal branch (BHB) stars in ω Centauri have been obtained using the multiobject fiber spectroscopic facility, Autofib, at the 3.9 m AAT. Preliminary analysis in the temperature range 7500K - 8200K indicates that a large fraction of BHB stars are at lower metallicities compared to the RR Lyrae stars and the giants. This could possibly be used to elucidate how mass loss efficiency varies with metallicity. The data can also be used together with simulated HBs to derive the variation of HB luminosity with metallicity.

We present a radial velocity survey of a sample of the field population of carbon stars in the outer parts of the Small Magellanic Cloud (SMC). This first set of results includes radial velocities for 71 carbon stars, with an individual precision of +/-2-5km/s. The mean heliocentric velocity of the stars (excluding one very high velocity star) is 149.3+/-3.0km/s with a velocity dispersion of 25.2+/-2.1km/s. These values drop to 145.5+/-2.7km/s and 20.6+/-1.9km/s respectively, if we exclude the stars belonging to the Outer Wing. The velocity distribution does not show the multiple peaks seen in some samples of Population I objects. The mass of the SMC as inferred from the above velocity dispersion (without the outer Wing stars) is =~1.2x109M☉. (2 data files).

A survey of carbon stars in the outer parts of the Small Magellanic Cloud has been completed; the candidate objects were identified by inspecting UK Schmidt Telescope objective-prism plates which cover a total area of ~220 sq deg on the sky, including the inter-Cloud region. Co-ordinates are given for 1185 newly identified carbon stars. (1 data file).

A new determination of the structural parameters of the dwarf spheroidals (dSphs) orbiting our Galaxy is presented. The morphology of the dSphs was determined from star counts made using photographic plates digitized and analysed using the APM facility at Cambridge. Global and central mass-to-light ratios were calculated for these galaxies. They range from ~=10 for Fornax and Sculptor to more than 200 for Draco. It appears plausible that Draco, Ursa Minor, Carina and Sextans contain significant amounts of dark matter, at least under the standard assumptions for the dynamics of these galaxies. However, the errors associated with these estimates remain - often forbiddingly - large, dominated (in most cases) by the errors in the luminosity and velocity dispersion. The possibility of the presence of extra-tidal stars in at least some of the dSphs is also discussed, together with the effect of the Galactic tidal field on the dSphs' morphology. Both Sextans and Sculptor appear to be good candidates for systems in the process of tidal disruption.

A survey of carbon stars in the outer parts of the Small Magellanic Cloud has been completed; the candidate objects were identified by inspecting UK Schmidt Telescope objective-prism plates which cover a total area of ~220sq.deg on the sky, including the inter-Cloud region. Co-ordinates, accurate to =~2arcsec, are given for 1185 newly identified carbon stars. The spatial distribution of the SMC carbon stars appears to be identical to that of red, horizontal-branch/clump stars found by Gardiner & Hatzidimitriou (1992).

A new catalogue of clusters in the Large Magellanic Cloud has been constructed from searches of the IIIa-J component of the ESO/SERC Southern Sky Atlas. The catalogue contains coordinate and diameter measurements of 1762 clusters in a 25x25{deg} area of sky centred on the LMC, but excluding the very crowded 3.5 square deg. region around the Bar. The distribution of these clusters appears as two superimposed elliptical systems. The higher density inner system extends over about 8d; the lower density outer system can be represented by 13d X 10d disc inclined at 42d to the line of sight. There are suggestions of two weak "arms" in the latter. (1 data file).

Extensive studies of red horizontal branch (clump) stars in the outer parts of the Small Magellanic Cloud (SMC) have suggested the presence of a large line-of-sight depth in the north-eastern region. A sample of red horizontal branch stars in the area of maximum depth was observed in 1989 December and 1990 December with the multi-object spectroscopic facility Autofib at the 3.9-m Anglo-Australian Telescope, with the purpose of deriving the velocity distribution for these stars. The data show a well- defined correlation between distance along the line of sight and radial velocity (corresponding to 8 km s^-1^ kpc^-1^), which may be interpreted as the result of the tidal interaction between the SMC and the LMC.

During the last decade several authors have undertaken extensive studies of the kinematics and structure of the Small Magellanic Cloud (SMC), which is generally thought to be affected by the dynamics of the triple interacting system consisting of the Galaxy and the Magellanic Clouds (MCs). In this paper we point out the importance of studying the kinematics of old rather than young populations when investigating the purely gravitational effects on the structure of the SMC of the previously mentioned tidal interaction. We also describe briefly the results obtained for such old stars in the NE 'corner'of the SMC.

Two very young clusters in the Large Magellanic Cloud (LMC), NGC 2098 ans SL 666, were selected for the search for mass segregation. Here we present te first results for NGC 2098. The analysis is still in progress and details will be published elsewhere. The present data confirm that the brightest main sequence stars of NGC 2098 are concentrated in the central 1.5 arcmin. The question now arises whether the cluster itself is indeed extended beyond 1.5 arcmin. Extensive star counts are now being performed in all directions and at large radii around NGC 2098 to help settle this question.

The fourth in a series of papers on the large-scale structure and stellar content of the Small Magellanic Cloud (SMC), based on photometric analysis of sets of blue and red UK Schmidt photographic plates, is presented here. The previous papers reviewed the data reduction procedures and presented results on the three-dimensional structure of a large sector of the outer regions of the SMC beyond 2^deg^ from the SMC centre. Here, we present a study of the age and spatial distribution of stellar populations in an area covering six UKST survey fields, i.e. virtually the entire outer area of the SMC. The existence of a very old stellar population of age 15-16 Gyr, comprising about 7 per cent of the stellar content of the outer regions by mass, is suggested by the observational results. However, the bulk of the stellar population in the outer regions of the SMC is found to be about 10 Gyr old. The distribution of stellar populations younger than about 2 Gyr is shown to be biased towards the eastern side of the SMC facing the LMC. The star formation history of the outer regions is discussed with particular reference to the role of interactions between the LMC-SMC-Galaxy system.

A new age indicator for star clusters and other stellar populations, with red horizontal branches or clumps, is introduced. This indicator is defined as the colour difference between the median colour of the red horizontal branch or clump and the red giant branch at the level of the horizontal branch. This difference is clearly independent of the values adopted for the reddening and distance modulus of the population as well as of systematic errors in the photometry and it is shown to be insensitive to metal abundance for a wide range of metallicities from solar values down to [Fe/H]~ - 1.7 dex. The theoretical predictions of stellar evolution models for this indicator are also examined. Finally, the new indicator is applied to colour-magnitude diagrams of star clusters with poorly known ages in our Galaxy, as well as to field populations in the Magellanic Clouds and the Carina dwarf spheroidal galaxy. At least one of the galactic disc globular clusters examined is found to have an age less than ~8 Gyr.

The AAT FOCAP fibre system has been used to obtain spectra, centred at the Ca II IR-triplet, of 14 stars in the field of the recently discovered Sextans dwarf spheroidal galaxy. Radial velocities derived from these spectra indicate that six of the stars observed are Sextans members. Their velocities cluster closely about a value of 230+/-6 km s^-1^ which we take as the heliocentric velocity of this galaxy. This velocity, when corrected to the galactic rest frame, indicates that Sextans makes a contribution comparable to those of other dSph galaxies, such as Sculptor and Orsa Minor, to calculations of the mass of the galaxy's halo. The spectra of the Sextans members also yield an estimate of the mean abundance of this galaxy: a value of [Fe/H] = - 1.7+/-0.25 dex is suggested from a comparison of the line strengths with those of globular cluster stars. This value is higher than that expected for Sextans from the absolute magnitude-abundance relation, followed by the other galactic dSph galaxies.

A photographic atlas of close pairs of star clusters in the Large Magellanie Cloud is presented here. The criterion for inclusion of cluster pairs in the atlas was an upper limit of 18.7 pc for the projected separation between the centres of the clusters in each pair. Accurate coordinates for the clusters, the projected separations and estimates of the diameters and positional angles are given and some of the global properties of the cluster-pair population of the LMC are discussed. It is found that the individual clusters in pairs preferentially have nearly equal sizes.

A study is undertaken of the 3D spatial distribution of the older stellar population lying beyond about 2 kpc in projected radial distance from the center of the SMC. The study is intended to cover 120 square degrees including six overlapping Schmidt fields. The results from an area of 80 square degrees are presented including the western, northern and northeastern outer parts of the SMC.

A new catalogue of clusters in the Large Magellanic Cloud has been constructed from searches of the IIIa-J component of the ESO/SERC Southern Sky Atlas. The catalogue contains coordinate and diameter measurements of 1762 clusters in a 25^deg^ x 25^deg^ area of sky centred on the LMC, but excluding the very crowded 3.5 deg^2^ region around the Bar. The distribution of there clusters appears as two superimposed elliptical systems. The higher density inner system extends over ~ 8^deg^; the lower density outer system can be represented by a 13^deg^ x 10^deg^ disc inclined at 42^deg^ to the line of sight. There are suggestions of two weak "arms" in the latter.

We have surveyed the cluster system of the SMC with the aim of identifying close pairs of clusters. We find that the number of existing close cluster pairs is significantly (at the 3.5 σ level) larger than the expected number of such pairs due to the chance line-up of single clusters, implying that some of these pairs are physically associated. Comparison with the LMC cluster system shows that the ratio of pairs is similar to the ratio of single clusters in the two galaxies. These results, combined with the earlier results for the LMC, indicate the tendency of clusters to form in pairs, or possibly in groups, at least in the case of irregular galaxies, the probability that the observed number of pairs having formed due to tidal capture being small.

An area of 48.5 square degrees covering the north-east and south-west outer regions of the Small Magellanic Cloud is studied with the use of the UK-Schmidt Telescope plates (taken from B_J_ and R filters). The plates were measured with the COSMOS microdensitometer and calibrated with a number of charge-coupled devices to observe sequences in the region. The resulting data set will be used for a detailed study of stellar populations and the geometry of the Small Magellanic Cloud outer regions. In this paper the production of the data set and an assessment of its accuracy are presented.

The three-dimensional (3D) distribution of the old disc and halo populations in the Small Magellanic Cloud (SMC) outlying (projected distances from the optical centre larger than 2kpc) north-eastern and south-western regions is presented. The magnitudes of the Horizontal Branch (HB)/clump stars in these regions are used as distance indicators. It is shown that in the north-eastern regions there is a significant line-of-sight depth of 17kpc on average, reaching a maximum value of 23kpc. These regions are ~10kpc deeper than the south-western regions. This result is attributed to the disruptive effect of the tidal field of the Large Magellanic Cloud (LMC) on the SMC. The possibility of the existence of two separate entities along the line-of-sight is examined.

The dynamical properties and stellar content of some cluster pairs in the LMC were studied, using UKST plates. Positive evidence was found for significant distortions in the density profiles of the clusters, particularly in the outer regions. These disturbances were interpreted as indications of dynamical interaction between the pair members. Some of the pairs were found to have very similar stellar content, and ages ranging from a few 107yr to several 108yr.

Available from UMI in association with The British Library. Requires signed TDF. The purpose of this study is to achieve an improved and more complete understanding of the structure and evolutionary history of the Small Magellanic Cloud, the second nearest galaxy to our own. The study was focused on the northeastern and west/southwestern outer parts of the SMC, including populations at projected distances larger than 2.2 kpc from the centre of the SMC. These regions have scarcely been studied in detail in the past. The observational material consisted of good quality B and R photographic plates taken with the U.K. Schmidt Telescope in Australia, digitised by the COSMOS automatic microdensitometer and calibrated by a series of CCD photometric sequences obtained at the European Southern Observatory (with the 1.5m Danish Telescope) and at the Anglo-Australian Observatory (with the 4m Telescope). Colour-magnitude diagrams were constructed over the whole of the area measured. The analysis of the properties of these diagrams resulted in (a) establishing the population synthesis in the outer parts of the SMC as a function of position with respect to the centre, and (b) probing the geometrical structure (in three dimensions) of these outlying regions of the SMC, which led to the discovery of a significant line-of-sight depth in the NE outer parts. A study of the carbon star population in the SMC outer regions was also conducted, using UKST prism plates. The carbon stars were used as probes of the intermediate-age populations in the outer parts of the SMC.

Most studies of the morphological and structural properties of the SMC to date were based on very young and young populations essentially confined in space to the bar, arms, and wing. In this project, the authors cover a much larger area of the SMC and a much broader range in ages, with the purpose of performing a thorough study of the structure and population synthesis in the outer regions of the SMC.

Thirty eight remote LMC clusters randomly distributed around the LMC rotation centre were measured by means of star counts in plates taken with the 1.2 m U.K. Schmidt telescope to derive their tidal radii and total masses. Seven of these clusters were found to violate the usual picture of a conventional density profile.

Spectral classification of stars in SMC clusters provide useful information on the evolutionary history of this galaxy and permit to test the theory of stellar evolution.

We have surveyed the LMC cluster system and have identified 69 double clusters with a centre-to-centre separation of less than ~1.3 arcmin (~18 pc). We infer that a considerable fraction of these double clusters must be binaries since the calculated projection effects can account for only 31 of them. This inference is strongly supported by the fact that the ages available for some of the clusters of our sample (as determined from UBV photometry) are less than the computed times of merger or disruption of the binary cluster system. Furthermore, the space distribution of these pairs indicates that these clusters belong to a very young or young population.

An investigation of the star clusters in the outermost areas of the LMC has started in order to examine the observed dynamical properties of the halo globular clusters in this galaxy. A first sample of 38 clusters have been measured by means of star counts on plates taken with the 1.2 m U.K. Schmidt telescope. The derived tidal radii and masses are comparable to those found for the disk young clusters of the LMC and those of the galactic globulars.

The existence of binary clusters in the Large Magellanic Cloud has been discussed recently. A survey of the LMC on UKSTU plates yielded a total of 69 pairs of clusters with a center-to-centre separation of less than ≡18 pc (for a distance modulus of 18.4 for the LMC). Statistical arguments suggest that taking chance line-ups into account, a significant fraction of the pairs found must be physically associated at the 7σ level. A series of observations have been undertaken in order to establish the physical association of the pairs.