The X-ray source content of the XMM-Newton Galactic plane survey

We report the results of an optical campaign carried out by the XMM-Newton Survey Science Centre with the specific goal of identifying the brightest X-ray sources in the XMM-Newton Galactic Plane Survey of Hands et al. (2004). In addition to photometric and spectroscopic observations obtained at the ESO-VLT and ESO-3.6m, we used cross-correlations with the 2XMMi, USNO-B1.0, 2MASS and GLIMPSE catalogues to progress the identification process. Active coronae account for 16 of the 30 positively or tentatively identified X-ray sources and exhibit the softes t X-ray spectra. Many of the identified hard X-ray sources are associated with massive stars, possibly in binary systems and emitting at intermediate X-ray luminosities of 10 32−34 erg s −1 . Among these are