Citation:
Bonfini P, Hatzidimitriou D, Pietsch W, Reig P. Spectroscopy of the bright optical counterparts of X-ray sources in the direction of M 31. [Internet]. 2009;507:705 - 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.