The X-ray source population of the metal-rich globular cluster NGC 6528

ABSTRACT We present the first study of the X-ray sources in one of the most metal-rich globular clusters in the Galaxy, NGC 6528. Using relatively deep (66 ks) archival imaging from the Chandra X-ray Observatory, we identify 18 sources within the half-light radius of the cluster, all in the range $L_X \sim 10^{31}$–$10^{32}$ erg s$^{-1}$ (0.5–7 keV). By combining these data with photometry from the Hubble Space Telescope and other sources, we classify the X-ray sources as a likely mix of cataclysmic variables and active binaries, though one or more of the brighter objects could be a quiescent low-mass X-ray binary. For this cluster, it appears that the X-ray binary-enhancing effects of high metallicity are outweighed by the cluster’s advanced dynamical evolution, leading to a relatively modest X-ray source population.