@article {23903, title = {Spectroscopy of the bright optical counterparts of X-ray sources in the direction of M 31}, volume = {507}, year = {2009}, month = {2009/11/1}, pages = {705 - 711}, abstract = {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.}, keywords = {Astrophysics - High Energy Astrophysical Phenomena, galaxies: individual: M 31, X-rays: galaxies, X-Rays: Stars}, isbn = {0004-6361}, url = {https://ui.adsabs.harvard.edu/abs/2009A\&A...507..705B}, author = {Bonfini, P. and Hatzidimitriou, D. and Pietsch, W. and Reig, P.} }