AAS 203rd Meeting, January 2004
Session 84 Binary Stars
Poster, Wednesday, January 7, 2004, 9:20am-6:30pm, Grand Hall

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[84.03] ClassX Detection of Hard X-Ray Binaries in ROSAT PSPC Data from pointed observations

A. A. Suchkov, R. J. Hanisch (STScI)

We present the results of a search for hard X-ray binaries (HXRB) using the automated X-ray source classifier ClassX (McGlynn et al. 2003). New candidate XRBs were identified among sources observed in ROSAT PSPC pointed observations and listed in the WGACAT catalog (http://wgacat/gsfc/nasa.gov) as unidentified objects. Hard sources were defined as those with count rate ratios in the 0.9-2.0 and 0.4-0.9 KeV bands greater than 10. Using ROSAT data only, ClassX identified 35 new HXRB candidates. This is to be compared with 33 known HXRBs in the WGACAT. Adding 2MASS source properties to the classifier increases the HXRB candidate count by another 50%. All but a few of the new HXRB candidates are located within 2 degrees of the Galactic plane, with substantial concentration toward the Galactic center. They are on average significantly fainter and apparently more distant. Quite a number of them are seen on the background of various nebulosities. All but one of the known and newly identified HXRBs were found to have 2MASS counterparts within 30 arcsec. Whether real counterparts or just spurious XRB neighbors, these 2MASS sources can probe the intervening absorbing material. Indeed, the 2MASS colors of the HXRBs proved to be much redder than those of the rest of the XRBs, and the newly identified HXRBs are noticeably redder than the previously known HXRBs. This is consistent with strong selective absorption being a major contributor to the hardness of the HXRBs and suggests that the faint HXRB population identified by ClassX is on average more distant and more obscured.

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Bulletin of the American Astronomical Society, 35#5
© 2003. The American Astronomical Soceity.