A Deep Census of Low-Luminosity X-ray Sources in Globular Cluster w Cen

We report the results of an analysis of a 290 kilosecond observation of Omega Centauri with the Chandra X-ray Observatory aimed at studying this globular cluster's population of X-ray emitting binary stars. Combining ACIS-I data from 2000 and 2012, we obtain a deep exposure that reaches a limiting flux of 5×10^{-16} erg/cm^2/s, or a luminosity of L_{X} ∼ 1.6×10^{30} erg/s for sources in the cluster. Given these limits, we expect to be sensitive to most cataclysmic variable stars and many coronally active stars (e.g., BY Draconis and RS CVn stars) in the cluster, as well as large numbers of active galactic nuclei in the background. We find a total of 302 sources in the 17'x17' field, 138 of which are newly reported here. We assess the fraction of these sources that are likely to be AGN by comparing our results to the Chandra Deep Field. We present an X-ray colour-magnitude diagram for all the sources and discuss its significance for distinguishing different types of X-ray emitting binary stars in the cluster. We also present some archival HST images of the brightest X-ray sources in this new sample.