Discovery of Hot Supergiant Stars near the Galactic Center

We report new results of a campaign to find Wolf-Rayet and O (WR/O) stars andhigh-mass X-ray binaries (HMXBs) in the Galactic center. We searched forcandidates by cross-correlating the 2MASS catalog with a deep Chandra catalogof X-ray point sources in the Radio Arches region. Following up with K-bandspectroscopy, we found two massive stellar counterparts to CXOGCJ174555.3-285126 and CXOGC J174617.0-285131, which we classify as a broad-linedWR star of sub-type WN6b and an O Ia supergiant, respectively. Their X-rayproperties are most consistent with those of known colliding-wind binaries inthe Galaxy and the Large Magellanic Cloud, although a scenario involvinglow-rate accretion onto a compact object is also possible. The O Ia star lies4.4 pc in projection from the Quintuplet cluster, and has a radial velocityconsistent with that of the Quintuplet, suggesting that this star might haveescaped from the cluster. We also present the discovery of a B2 Ia supergiant,which we identified as a candidate massive star using 8 micron Spitzer maps ofthe Galactic center in a region near the known massive X-ray-emitting starCXOGC J174516.1-290315. We discuss the origin of these stars in the context ofevolving stellar clusters in the Galactic center.Comment: 21 pages, 5 figures, accepted for publication in the Astrophysical Journa