@article {41760, title = {EXTraS discovery of two pulsators in the direction of the LMC: a Be/X-ray binary pulsar in the LMC and a candidate double-degenerate polar in the foreground}, volume = {598}, year = {2017}, month = {2017/02/1}, pages = {A69}, abstract = {Context. The Exploring the X-ray Transient and variable Sky (EXTraS) project searches for coherent signals in the X-ray archival data of XMM-Newton.
Aims: XMM-Newton performed more than 400 pointed observations in the region of the Large Magellanic Cloud (LMC). We inspected the results of the EXTraS period search to systematically look for new X-ray pulsators in our neighbour galaxy.
Methods: We analysed the XMM-Newton observations of two sources from the 3XMM catalogue which show significant signals for coherent pulsations.
Results: 3XMM J051259.8-682640 was detected as a source with a hard X-ray spectrum in two XMM-Newton observations, revealing a periodic modulation of the X-ray flux with 956 s. As optical counterpart we identify an early-type star with Hα emission. The OGLE I-band light curve exhibits a regular pattern with three brightness dips which mark a period of 1350 d. The X-ray spectrum of 3XMM J051034.6-670353 is dominated by a super-soft blackbody-like emission component (kT 70 eV) which is modulated by nearly 100\% with a period of 1418 s. From GROND observations we suggest a star with r{\textquoteright} = 20.9 mag as a possible counterpart of the X-ray source.
Conclusions: 3XMM J051259.8-682640 is confirmed as a new Be/X-ray binary pulsar in the LMC. We discuss the long-term optical period as the likely orbital period which would be the longest known from a high-mass X-ray binary. The spectral and temporal properties of the super-soft source 3XMM J051034.6-670353 are very similar to those of RX J0806.3+1527 and RX J1914.4+2456 suggesting that it belongs to the class of double-degenerate polars and is located in our Galaxy rather than in the LMC.}, keywords = {Astrophysics - High Energy Astrophysical Phenomena, Be, binaries: close, CATACLYSMIC VARIABLES, galaxies: star clusters: individual: Large Magellanic Cloud, galaxies: stellar content, Novae, stars: emission-line, stars: neutron}, isbn = {0004-6361}, url = {https://ui.adsabs.harvard.edu/abs/2017A\&A...598A..69H}, author = {Haberl, F. and Israel, G. L. and Rodriguez Castillo, G. A. and Vasilopoulos, G. and Delvaux, C. and de Luca, A and Carpano, S. and Esposito, P. and Novara, G. and Salvaterra, R. and Tiengo, A. and D{\textquoteright}Agostino, D. and Udalski, A.} }