Binary black hole (BH) central engine description for the unique blazar OJ 287 predicted that the next secondary BH impact-induced bremsstrahlung flare should peak on 2019 July 31. This prediction was based on detailed general relativistic modeling of the secondary BH trajectory around the primary BH and its accretion disk. The expected flare was termed the Eddington flare to commemorate the centennial celebrations of now-famous solar eclipse observations to test general relativity by Sir Arthur Eddington. We analyze the multi-epoch Spitzer observations of the expected flare between 2019 July 31 and 2019 September 6, as well as baseline observations during 2019 February-March. Observed Spitzer flux density variations during the predicted outburst time display a strong similarity with the observed optical pericenter flare from OJ 287 during 2007 September. The predicted flare appears comparable to the 2007 flare after subtracting the expected higher base-level Spitzer flux densities at 3.55 and 4.49 μm compared to the optical R-band. Comparing the 2019 and 2007 outburst lightcurves and the previously calculated predictions, we find that the Eddington flare arrived within 4 hr of the predicted time. Our Spitzer observations are well consistent with the presence of a nano-Hertz gravitational-wave emitting spinning massive binary BH that inspirals along a general relativistic eccentric orbit in OJ 287. These multi-epoch Spitzer observations provide a parametric constraint on the celebrated BH no-hair theorem.

The existence of magnetic activity on the eclipsing binary DV Psc has been known for almost two decades. However, until recently, no evidence of periodic behaviour relevant to this activity had been found. In this study, long-term photometric observations of DV Psc are used to analyze the system's magnetic activity, seek a possible magnetic cycle and determine orbital and physical parameters. The combination of photometric and spectroscopic observations results in a unified model that describes the system over time in terms of variable spot activity. New times of minimum light are determined and an accurate astronomical ephemeris and updated O-C diagram are constructed for a total span of 19 years (1997-2017). The intense magnetic activity, as indicated by strong asymmetries in the light curves (O' Connell effect), and the periodic variation of the O-C diagram are combined to explain the system's behaviour. The existence of a third body, orbiting the eclipsing binary in an eccentric orbit, as well as a magnetic cycle are the most likely scenario.

W Ursae Majoris-type binaries belong to the old population of our Galaxy, while their metallicity is close to solar. Their physical properties, kinematics and spatial distribution reflect the properties of their stellar progenitors. This study focuses on the spatial distribution of W UMa's in our solar neighborhood within a 500 pc radius, with a combined astrometric, photometric and spectroscopic determination of their stellar parameters. The sample is carefully selected, in order to fulfill certain criteria, and has well defined metallicity and distance parameters. H-R diagram, as well as similar correlation plots (mass-radius and mass-luminosity), show that the primary (more massive) components in such systems are located close or below the ZAMS region, while secondary components seem to be evolved, as a result of their common envelope geometry. Some prominent outliers are carefully examined in order to judge the environmental properties and evolution in certain locations of the Milky Way. It is found that metallicity is not correlated with distance, but there is a weak correlation between metallicity [M/H] and evolution state, as it is expressed by the location of the systems in the H-R diagram, the type of binary (A or W), and temperature.

The evolution of eclipsing binaries leads towards angular momentum and mass loss from the systems, due to stellar wind and magnetic braking. Observational investigations of low-temperature and low-mass contact binaries (or LMCBs) in the solar neighborhood provide the means for studying a large sample of such systems. The observed orbital period cut-off limit of 0.22 days is believed to be a result of evolutionary mechanisms, and such systems act as probes in investigating the very evolved stages of systems before their final coalescence. The main goal of this study is the determination of the stellar evolution tracks of these type of LMCBs, which might be correlated to the formation of blue stragglers and rapidly rotating stars.

We report the discovery of the relatively bright (V = 10.5 mag), doubly eclipsing 2+2 quadruple system CzeV1731. This is the third known system of its kind, in which the masses are determined for all four stars and both the inner and outer orbits are characterized. The inner eclipsing binaries are well-detached systems moving on circular orbits: pair A with period PA = 4.10843 d and pair B with PB = 4.67552 d. The inner binaries contain very similar components (q ≈ 1.0), making the whole system a so-called double twin. The stars in pair B have slightly larger luminosities and masses and pair A shows deeper eclipses. All four components are main-sequence stars of F/G spectral type. The mutual orbit of the two pairs around the system barycenter has a period of about 34 yr and an eccentricity of about 0.38. However, further observations are needed to reveal the overall architecture of the whole system, including the mutual inclinations of all orbits. This is a promising target for interferometry to detect the double at about 59 mas and ΔMbol < 1 mag. The RV and ETV data, and the light curves 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/642/A63

The so-called "primordial family", is a recently discovered collisional family [1] that could be as old as the Solar system. It contains low-albedo asteroids and is located in the inner Main Belt. This family was identified by the V-shape technique [2] and is estimated to be at least 4 Gyr old, meaning that occurred before the giant planet instability [3]. Asteroids 2768 Gorky (1972 RX3) and 9086 (1995 SA3) are members of the primordial family and have been observed in order to determine their rotational period, spin pole and shape, which will give insights about their membership and the family evolution. The photometric data are obtained mainly by the University of Athens Observatory (UOAO) [4]. Models of the asteroids are derived by the lightcurve inversion method, which is stored in the Database of Asteroid Models from Inversion Techniques (DAMIT) [5].1. IntroductionThe so-called primordial family formed by an impact event 4 Gyr ago or even earlier, i.e. before the giant planet instability [3]. The identification of the primordial family has been done by using the V-shape technique [2]. The V-shape in (α,1/D) space is occurred due to the thermal Yarkovsky effect [6, 7, 2], where prograde-rotating asteroids drifting outwards and retrograde ones inward. As only the inward side of the V-shape of the primordial family is well defined, the members should have retrograde spin. Otherwise, the membership of asteroids with prograde spin could be disputed or the contradicting spin sense could be due to YORP cycles or a collision or a close encounter with other asteroid [8, 9]. Thus, it is essential to observe thoroughly the asteroids belonging to the primordial family, in order to determine their rotational state and shape.2. ObservationsAsteroid 2768 Gorky (1972 RX3) is member of the primordial asteroid family of the inner main belt [1]. Its rotational period is 4.507 ± 0.010 h [10], while its spin pole and shape remain unknown. Observations from Sopot Astronomy Observatory (SAO) for 2 nights in September 2019, in phase angle of 32°, are available in Asteroid Lightcurve Photometry Database (ALCDEF)[11] and present a period of 4.445 ± 0.003 h [12]. On the Observatoire de Genève website of R. Behrend [13] rotational period of the asteroid was reported to be 4.5118 ± 0.0007 h. Asteroid 2768 Gorky (1972 RX3) has been observed from UOAO for 5 nights in December 2019, in phase angles between 10° to 14°.Asteroid 9086 (1995 SA3) is member of the primordial asteroid family in the inner main belt [1]. Its rotational period, spin pole and shape remain unknown. UOAO has been observed this asteroid for 22 nights from October to November 2019, in phase angle ranging between 4° to 22°.3. Methodology and Preliminary ResultsDifferential photometry of the asteroid has been obtained for each sky field. All images were dark and flat-field corrected and unguided. The measured values are in magnitudes and have been transformed properly in relative flux. The determination of the rotational period of the two asteroids and the estimation of the spin pole and shape of 2768 Gorky (1972) has been carried out through the lightcurve inversion method stored in DAMIT [5]. 3.1 Asteroid 2768 Gorky (1972 RX3) The lightcurve of asteroid 2768 Gorky (1972 RX3) present a low amplitude of ~0.1 mag (or ~0.1 intensity units), as Figure 1 shows. Generating 50 random spin poles as initial input for DAMIT software, the results have the distribution presented in Figure 2. The plot in this figure constrains the possible spin poles of the asteroid, while the χ2 value and the dark facet percentage should have the lowest value. 3.2 Asteroid 9086 (1995 SA3) The lightcurve of asteroid 9086 (1995 SA3) present also a low amplitude of ~ 0.2 mag (or ~0.2 intensity units). The low brightness of the object in combination with the low amplitude of its lightcurve render the detection of its periodicity difficult, due to the background noise. In order to address this problem, the exposures of each night were combined in packs of 3, in order to increase the S/N and make the detection of light variation more prominent. The resulted period spectrum from DAMIT is presenting in Figure 3. 4. Summary and Conclusions The rotational period of 2768 Gorky (1972 RX3) has been calculated as 4.510 ± 0.020 h, in agreement with the literature. The spin pole is not defined well enough. It is needed observations from more than one apparition for more robust results. Asteroid 9086 (1995 SA3), despite the extensive observations, does not present a clear lightcurve, as a result to have not unique solution in the period. 5. Further work The determination of asteroids" rotational state and shape requires observations from more than one apparition. Alternatively, combing the already ground based with sparse data from sky surveys or space-borne could also drive to unique solutions. Acknowledgements We would to acknowledge Dr. Hanus J. for his valuable help and advices for the lightcurve analysis that performed. References [1] Delbo, M. et al. (2017). Science, 357, 1026-1029. [2] Bolin, B. T. et al. (2017). Icarus, 282, 290-312. [3] Tsiganis, K., et al. (2005). Nature, 435(7041), 459-461. [4] Gazeas, K. (2016). Revista Mexicana de Astronomía y Astrofísica, 48, 22-23. [5] Ďurech, J. et al. (2010). Astronomy & Astrophysics, 513, A46. (DAMIT"s website: astro.troja.mff.cuni.cz) [6] Milani, A. et al. (2014). Icarus, 239, 46-73. [7] Spoto, F. et al. (2015). Icarus, 257, 275-289. [8] Carruba, V. et al. (2013). Monthly Notices of the Royal Astronomical Society, 433(3), 2075-2096. [9] Delisle, J. B., & Laskar, J. (2012). Astronomy & Astrophysics, 540, A118. [10] Pray, D. P. et al. (2008). Minor Planet Bulletin, 35, 34-36. [11] Asteroid Lightcurve Photometry Database (ALCDEF)"s website: alcdef.org [12] Benishek, V. (2020). Minor Planet Bulletin, 47(1), 75-83. [13] Observatoire de Genève, Website of R. Behrend: obswww.unige.ch/~behrend

Planets In Your Hand is a science education program, that consists of a portable interactive exhibition of eight planetary surface models. The program offers the visitors a tactile experience and the opportunity to understand the diversity of the planetary surfaces in our Solar System. The planetary models have been exhibited in a series of public events since their construction in 2018 and have been visited by a wide range of audience, including visually impaired people. The project is still running, while Planets In Your Hand team is working on improvements, that foresee to a greater social and educational impact. The current work summarizes the social impact of the program through the visitors" questionnaires, comments and impressions.1. IntroductionPlanets In Your Hand (PIYH) is a science communication project, initiated at the Department of Physics of National and Kapodistrian University of Athens (NKUA). Its purpose is to reach individuals, that do not have any previous interaction with the field, trigger their interest to interactively participate in scientific activities and public events and eventually bring them closer to science and contribute in lifelong learning. This is mainly attempted through a visual and tangible representation of the planetary environments and morphologies in our Solar System (Kefala et al., 2018), that also benefits visually impaired people.The success of PIYH project is established by the Science Communication Award (EΠI2 Award 2019) in the category of "Awareness Activities and Campaigns".PIYH program is a non-formal learning experience, the importance of which is widely accepted and supported by the National Science Education Standards (National Research Council, 1996). The way science communication is organized and planned as well as the visitor"s intrinsic motivation for learning (Eshach 2007) declares this an indisputable fact.2. Data CollectionIn order to evaluate the social impact of the PIYH project, questionnaires were filled out by the visitors after their conceivable journey to our Solar System. Multiple-choice questions and a comment section were included. The goal was to examine whether the exhibition provides an overall positive experience to the visitors and to find possible ways to improve its presentation.The planetary models have been exhibited in a series of public events (Fig. 1) since the beginning of the program (Palafouta et al., 2019). This research was conducted during two major events where PIYH was presented. These are the opening of the exhibition and the Athens Science Festival 2019.Oral impressions and evaluations for every event were also made directly by the members of the PIYH team that presented the planetary surfaces. They were based on the reactions and the comments of the visitors and were really helpful. PIYH program is a non-formal learning experience, the importance of which is widely accepted and supported by the National Science Education Standards (National Research Council, 1996). The way science communication is organized and planned as well as the visitor"s intrinsic motivation for learning (Eshach 2007) declares this an indisputable fact.3. The social impactThe questionnaire provided an overall positive feedback by the visitors. As shown in Fig. 2 the majority (97.5 %) of the visitors were pleased with PIYH project and the exhibition. Early ages (≤23 years old) occupy great percentage (61 %) of the visitors, while the rest include individuals, parents or educators.The overwhelming majority of the participants (98.5%) would recommend the exhibition to a friend, enhancing the social impact of the project, while many parents and educators mentioned that this project can trigger new generations to engage with Astrophysics and science in general.More than 47% of the visitors shared their impressions through additional comments. Positive remarks were given, for the exhibition and its presentation by the PIYH team members.Visually impaired people commented positively, mentioning that exhibitions in general do not offer tangible experience, and they are limited to an oral, acoustic or pre-recorded presentation. PIYH exhibition gave them for the first time the sense of planetary scale, surface characteristics and the unique opportunity to interact with planetary surfaces.A wide range of reactions was perceived by the PIYH team members during the events with respect to the visitor"s background in astrophysics.Regardless of their age, people who were getting in touch with Planetary Science for the first time were curious to touch and feel the surface"s differences, asking questions about the internal and external structure and the atmospheric phenomena of each planet. Those who had scientific background, combined facts and knowledge from their own scientific field with the information provided during the events.On the other hand, visitors familiar with astronomy and planetary science expressed more elaborate questions, many of which concerned the current research on space exploration.4. Summary and ConclusionsThis research has shown that people of different age and scientific background can be brought together through an interactive and tangible educational experience. PIYH exhibition is considered a pleasant and memorable experience according to the conducted analysis. The project attracted individuals that have no previous interaction with the field of Planetary Science, triggering their interest and brought together people who are already interested or contribute to science. PIYH project makes this learning experience accessible to visually impaired people, encouraging this way the local community to create similar activities. It is an alternative, creative and interesting way of learning about our Solar System. Similar projects can be inspired by PIYH program and engage the general public in science through a pleasant and cognitively successful way, enhancing the communication of science in many fields.References[1] Eshach, H., 2007, Journal of Science Education and Technology, 16, 171-190.[2] Kefala, K., et al., 2018, EPSC2018,1251-2.[3] National Research Council, 1996.National Science Education Standards. Washington DC: National Academy Press.[4] Palafouta, S., et al., 2019, EPSC-DPS2019, 1816-1

We present new photometric and spectroscopic observations and analyses for the eclipsing binary systems V1241 Tau and GQ Dra. Our photometric light and radial velocity curve analyses combined with the TESS light curves show that both are conventional semi-detached binary systems. Their absolute parameters are also derived. We present the O-C analyses of the systems and we propose the most possible orbital period modulating mechanisms. Furthermore, Fourier analyses are applied to the photometric residual data of the systems to check for the pulsational behavior of the components. We conclude that the primary component of the system GQ Dra is a δ Sct type pulsator with a dominant pulsation frequency of 18.58 d-1 based on our B filter residual light curve although it can not be justified by 30-minute cadence TESS data. No satisfactory evidence of pulsational behavior for V1241 Tau was verified. Finally, the evolutionary tracks of the components of both systems are calculated. Their locations within evolutionary diagrams are compared with other Algol-type systems

The discovery and analysis of the system CzeV1731 represents a rare configuration of a 2+2 quadruple star system containing two eclipsing binaries, the third system of its kind known to date. The system under investigation in this work is TYC 3929-724-1 (= 2MASS J19245582+5704084 = TIC 284482112), located at RA=19:24:55.82, DE=+57:04:08.39, with Vmax=10.5mag. We present times of eclipses and radial velocities of both pairs. (2 data files).

Table 1 includes the data from the astrometric monitoring runs for 2002 TC302 carried out to narrow down the shadow path uncertainty, in October, November, December 2017 and January 2018 with the Sierra Nevada 1.5m telescope (Granada, Spain) and the Calar Alto 1.2m telescope (Almeria, Spain). The astrometric catalog used for the occultation prediction was Gaia DR1. Tables 2 and 3 include, respectively, all the photometry and astrometry of 2002 TC302 analyzed, from 2014 to 2019. The astrometry was derived with respect to the Gaia DR2 catalog (Cat. I/345). (3 data files).

Context. Deriving physical properties of trans-Neptunian objects is important for the understanding of our Solar System. This requires observational efforts and the development of techniques suitable for these studies. Aims: Our aim is to characterize the large trans-Neptunian object (TNO) 2002 TC302. Methods: Stellar occultations offer unique opportunities to determine key physical properties of TNOs. On 28 January 2018, 2002 TC302 occulted a mv ~ 15.3 star with designation 593-005847 in the UCAC4 stellar catalog, corresponding to Gaia source 130957813463146112. Twelve positive occultation chords were obtained from Italy, France, Slovenia, and Switzerland. Also, four negative detections were obtained near the north and south limbs. This represents the best observed stellar occultation by a TNO other than Pluto in terms of the number of chords published thus far. From the 12 chords, an accurate elliptical fit to the instantaneous projection of the body can be obtained that is compatible with the near misses. Results: The resulting ellipse has major and minor axes of 543 ± 18 km and 460 ± 11 km, respectively, with a position angle of 3 ± 1 degrees for the minor axis. This information, combined with rotational light curves obtained with the 1.5 m telescope at Sierra Nevada Observatory and the 1.23 m telescope at Calar Alto observatory, allows us to derive possible three-dimensional shapes and density estimations for the body based on hydrostatic equilibrium assumptions. The effective diameter in equivalent area is around 84 km smaller than the radiometrically derived diameter using thermal data from Herschel and Spitzer Space Telescopes. This might indicate the existence of an unresolved satellite of up to ~300 km in diameter, which is required to account for all the thermal flux, although the occultation and thermal diameters are compatible within their error bars given the considerable uncertainty of the thermal results. The existence of a potential satellite also appears to be consistent with other ground-based data presented here. From the effective occultation diameter combined with absolute magnitude measurements we derive a geometric albedo of 0.147 ± 0.005, which would be somewhat smaller if 2002 TC302 has a satellite. The best occultation light curves do not show any signs of ring features or any signatures of a global atmosphere. Tables A.1-A.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/639/A134

Context. EE Cep is one of few eclipsing binary systems with a dark, dusty disc around an invisible object similar to ɛ Aur. The system is characterised by grey and asymmetric eclipses every 5.6 yr that have significant variations in their photometric depth, ranging from ∼0.m5 to ∼2.m0. Aims: The main aim of the observational campaign of the EE Cep eclipse in 2014 was to test the model of disc precession. We expected that this eclipse would be one of the deepest with a depth of ∼2.m0. Methods: We collected multicoloured observations from almost 30 instruments located in Europe and North America. These photometric data cover 243 nights during and around the eclipse. We also analyzed low- and high-resolution spectra from several instruments. Results: The eclipse was shallow with a depth of 0.m71 in the V band. The multicoloured photometry illustrates small colour changes during the eclipse with a total amplitude of order ∼+0.m15 in the B - I colour index. We updated the linear ephemeris for this system by including new times of minima, measured from the three most recent eclipses at epochs E = 9, 10, and 11. We acquired new spectroscopic observations, covering orbital phases around the eclipse, which were not observed in the past and increased the data sample, filling some gaps and giving better insight into the evolution of the Hα and Na I spectral line profiles during the primary eclipse. Conclusions: The eclipse of EE Cep in 2014 was shallower than expected, measuring 0.m71 instead of ∼2.m0. This means that our model of disc precession needs revision. Tables A1-A29 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/639/A23