Isolated, Massive Supergiants near the Galactic Center

We have carried out a pilot project to assess the feasibility of using radio, infrared, and X-ray emission to identify young, massive stars located between 1 and 25 pc from the Galactic center. We first compared catalogs compiled from the Very Large Array, the Chandra X-ray Observatory, and 2MASS. We identified two massive, young stars: the previously-identified star that is associated with the radio HII region H2, and a newly-identified star that we refer to as CXOGC J174516.1-290315. The infrared spectra of both stars exhibit very strong Brackett-γ and He I lines, and resemble those of massive supergiants that have evolved off of the main sequence, but not yet reached the WolfRayet phase. We estimate that each star has a bolometric luminosity &10L⊙. These two stars are also associated with bright mid-infrared sources from the Midcourse Space Experiment survey, although the origin of this emission is uncertain. Likewise, the detection of these two sources in Xrays is surprising, because stars at similar evolutionary states are not uniformly bright X-ray sources. Therefore, we suggest that both stars are in binary systems that contain either OB stars whose winds collide with those of the luminous supergiants, or compact objects that are accreting from the winds of the supergiants. We also identify X-ray emission from a nitrogen-type Wolf-Rayet star and place upper limits on the X-ray luminosities of three more evolved, massive stars that previously have been identified between 1 and 25 pc from Sgr A*. Finally, we briefly discuss the implications that future searches for young stars will have for our understanding of the recent history of star formation near the Galactic center. Subject headings: stars: emission-line — Galaxy: center — radio continuum: stars — infrared: stars — X-rays: stars