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D. Haggard, J.L. Carlin, A.M. Cool (San Francisco State University), B. Zhao, C.D. Bailyn (Yale University), P.D. Edmonds, J.E. Grindlay (Harvard University), M.B. Davies (University of Leicester)
We report findings from a ~70 ksec Chandra observation of the globular cluster Omega Cen (NGC 5139) taken in order to study its population of X-ray emitting binary stars. About 175 X-ray sources with luminosities as faint as Lx ~ 2x1030 erg/sec are detected in the ~17' x 17' field of the Advanced CCD Imaging Spectrometer (ACIS-I) centered on the cluster's core. We estimate that ~30 to 40 of these sources are likely to be cluster members. We present timing and preliminary spectral analyses of the brightest of these sources, and initial results of efforts to identify optical counterparts in existing HST and ground-based data. Using the <1 arcsec positions derived from Chandra we confirm our previous Hubble Space Telescope (HST) identification of two of the sources in the cluster core as cataclysmic variables (Carson, Cool, and Grindlay 2000). We also identify two other sources as RS CVn and Algol-type binaries found in the OGLE survey (Kaluzny et al. 1996). One X-ray source at ~2 core radii has X-ray properties similar to the quiescent LMXBs recently identified in 47 Tuc and NGC 6397 (Grindlay et al. 2001a,b). We compare our results for Omega Cen to those of other clusters for which long-exposure Chandra studies have been undertaken. Support for this work was provided by NASA through Chandra award GO0-1040A issued by the Chandra X-ray Observatory Center.
The author(s) of this abstract have provided an email address for comments about the abstract: dhaggard@stars.sfsu.edu
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Bulletin of the American Astronomical Society, 34
© 2002. The American Astronomical Soceity.