2009/11/30 by C. Motch, R. S. Warwick, R. Warwick +17 · 38 citations
Physics and Astronomy · #Astronomy #Astrophysical Phenomena and Observations #Astrophysics #Astrophysics and Star Formation Studies #Binary number #Emission spectrum #Galactic plane #Galaxy #Luminosity #Neutron star #Physics #Spectral line #Stars #Stellar, planetary, and galactic studies #Supergiant #Wolf–Rayet star #X-ray #X-ray binary #astro-ph.GA #astro-ph.HE #astro-ph.SR
paper · pdf · doi:10.1051/0004-6361/200913570
published in Astronomy and Astrophysics 523, A92 (EDP Sciences) · 29 pages, 33 figures, revised version accepted for publication in Astronomy & Astrophysics. Title modified according to A&A rules, extended finding charts and tables. The results of this study remain unchanged. Full version with all spectra and finding charts available at http://astro.u-strasbg.fr/~motch/xgps_VA.pdf
arxiv created 2010/07/07 · openalex publication_date 2010/08/10 · arxiv updated 2015/05/14 · openalex created_date 2025/10/10 · openalex updated_date 2026/08/05
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. In addition to photometric and spectroscopic observations obtained at the ESO-VLT and ESO-3.6 m, we used cross-correlations with the 2XMMi, USNO-B1.0, 2MASS, and GLIMPSE catalogues to advance the identification process. Active coronae account for 16 of the 30 positively or tentatively identified X-ray sources and exhibit the softest X-ray spectra. Many of the identified hard X-ray sources are associated with massive stars, possible members of binary systems and emitting at intermediate X-ray luminosities of 1032−34 erg s-1. Among these are (i) a very absorbed, likely hyper-luminous star with X-ray/optical spectra and luminosities comparable to those of η Carina; (ii) a new X-ray-selected WN8 Wolf-Rayet star in which most of the X-ray emission probably arises from wind collision in a binary; (iii) a new Be/X-ray star belonging to the growing class of γ-Cas analogues; and (iv) a possible supergiant X-ray binary of the kind discovered recently by INTEGRAL. One of the sources, XGPS-25, has a counterpart of moderate optical luminosity that exhibits HeII λ4686 and Bowen CIII-NIII emission lines, suggesting that this may be a quiescent or X-ray shielded low mass X-ray binary, although its X-ray properties might also be consistent with a rare kind of cataclysmic variable (CV). We also report the discovery of three new CVs, one of which is a likely magnetic system displaying strong X-ray variability. The soft (0.4–2.0 keV) band log N(>S) − log S curve is completely dominated by active stars in the flux range of 1 × 10-13 to 1 × 10-14 erg cm-2 s-1. Several active coronae are also detected above 2 keV suggesting that the population of RS CVn binaries contributes significantly to the hard X-ray source population. In total, we are able to identify a large fraction of the hard (2–10 keV) X-ray sources in the flux range of 1 × 10-12 to 1 × 10-13 erg cm-2 s-1 with Galactic objects at a rate consistent with what is expected for the Galactic contribution alone.