Optical Identification of Multiple Faint X‐Ray Sources in the Globular Cluster NGC 6752: Evidence for Numerous Cataclysmic Variables1

We report on the Chandra ACIS-S3 imaging observation of the globular clusterNGC 6752. We detect 6 X-ray sources within the 10.5" core radius and 13 morewithin the 115" half-mass radius down to a limiting luminosity of Lx approx10^{30} erg/s for cluster sources. We reanalyze archival data from the HubbleSpace Telescope and the Australia Telescope Compact Array and make 12 opticalidentifications and one radio identification. Based on X-ray and opticalproperties of the identifications, we find 10 likely cataclysmic variables(CVs), 1-3 likely RS CVn or BY Dra systems, and 1 or 2 possible backgroundobjects. Of the 7 sources for which no optical identifications were made, weexpect that ~2-4 are background objects and that the rest are either CVs orsome or all of the five millisecond pulsars whose radio positions are not yetaccurately known. These and other Chandra results on globular clusters indicatethat the dozens of CVs per cluster expected by theoretical arguments are beingfound. The findings to date also suggest that the ratio of CVs to other typesof X-ray sources is remarkably similar in clusters of very different structuralparameters.Comment: 15 pages, 6 figures, accepted by ApJ, minor changes in response to referee's comment