The MAVERIC Survey: Chandra/ACIS Catalog of Faint X-Ray Sources in 38 Galactic Globular Clusters

Abstract

Abstract Globular clusters host a variety of lower-luminosity (L X < 1035 erg s−1) X-ray sources, including accreting neutron stars (NSs) and black holes (BHs), millisecond pulsars (MSPs), cataclysmic variables, and chromospherically active binaries. In this paper, we provide a comprehensive catalog of more than 1100 X-ray sources in 38 Galactic globular clusters (GCs) observed by the Chandra X-ray Observatory’s Chandra/ACIS detector. The targets are selected to complement the MAVERIC survey’s deep radio continuum maps of Galactic GCs. We perform photometry and spectral analysis for each source, determine a best-fit model, and assess the possibility of it being a foreground or background source based on its spectral properties and location in the cluster. We also provide basic assessments of variability. We discuss the distribution of X-ray binaries in GCs and their X-ray luminosity function, and we carefully analyze systems with L X > 1033 erg s−1. Among these moderately bright systems, we discover a new source in NGC 6539 that may be a candidate accreting stellar-mass BH or a transitional MSP. We show that quiescent NS low-mass X-ray binaries in GCs may spend ∼2% of their lifetimes as transitional MSPs in their active (L X > 1033 erg s−1) state. Finally, we identify a substantial underabundance of bright (L X > 1033 erg s−1) intermediate polars in GCs compared to the Galactic field, in contrast with the literature of the past two decades.