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Description
We identify 233 X-ray sources, of which 95 are new, in a 222ks exposure of omega Centauri with the Chandra X-ray Observatory's Advanced CCD Imaging Spectrometer detector. The limiting unabsorbed flux in the core is fX(0.5-6.0keV)~=3x10^-16^erg/s/cm^2^ (Lx~=1x10^30^erg/s at 5.2kpc). We estimate that ~60+/-20 of these are cluster members, of which ~30 lie within the core (r_c_=155-arcsec), and another ~30 between 1-2 core radii. We identify four new optical counterparts, for a total of 45 likely identifications. Probable cluster members include 18 cataclysmic variables (CVs) and CV candidates, one quiescent low-mass X-ray binary, four variable stars, and five stars that are either associated with omega Cen's anomalous red giant branch or are sub-subgiants. We estimate that the cluster contains 40+/-10 CVs with Lx>10^31^erg/s, confirming that CVs are underabundant in omega Cen relative to the field. Intrinsic absorption is required to fit X-ray spectra of six of the nine brightest CVs, suggesting magnetic CVs, or high-inclination systems. Though no radio millisecond pulsars (MSPs) are currently known in omega Cen, more than 30 unidentified sources have luminosities and X-ray colours like those of MSPs found in other globular clusters; these could be responsible for the Fermi-detected gamma-ray emission from the cluster. Finally, we identify a CH star as the counterpart to the second brightest X-ray source in the cluster and argue that it is a symbiotic star. This is the first such giant/white dwarf binary to be identified in a globular cluster.
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