Issue A&A Volume 507, Number 2, November IV 2009 Page(s) 705 - 711 Section Extragalactic astronomy DOI 10.1051/0004-6361/200912508 Published online 08 September 2009

A&A 507, 705-711 (2009)
DOI: 10.1051/0004-6361/200912508

Spectroscopy of the bright optical counterparts of X-ray sources in the direction of M 31

P. Bonfini¹, D. Hatzidimitriou^{1, 2}, W. Pietsch³, and P. Reig<sup>2, 1

1</sup>  University of Crete, Department of Physics, PO Box 2208, 71003, Heraklion, Greece
    e-mail: paolo@physics.uoc.gr
²  IESL, Foundation for Research and Technology, 71110, Heraklion, Greece
³  Max-Planck-Institut für extraterrestrische Physik, 85741 Garching, Germany

Received 15 May 2009 / Accepted 17 July 2009

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.

Key words: galaxies: individual: M 31 -- X-rays: galaxies -- X-rays: stars

© ESO 2009

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