The MAVERIC Survey: Chandra/ACIS Catalog of Faint X-Ray Sources in 38 Galactic Globular Clusters
Abstract
Globular clusters host a variety of lower-luminosity (LX < 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 LX > 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 (LX > 1033 erg s-1) state. Finally, we identify a substantial underabundance of bright (LX > 1033 erg s-1) intermediate polars in GCs compared to the Galactic field, in contrast with the literature of the past two decades.
- Publication:
-
The Astrophysical Journal
- Pub Date:
- September 2020
- DOI:
- arXiv:
- arXiv:2007.04581
- Bibcode:
- 2020ApJ...901...57B
- Keywords:
-
- Globular star clusters;
- Low-mass x-ray binary stars;
- Neutron stars;
- Astrophysical black holes;
- Stellar accretion disks;
- Celestial objects catalogs;
- 656;
- 939;
- 1108;
- 98;
- 1579;
- 212;
- Astrophysics - High Energy Astrophysical Phenomena
- E-Print:
- 35 pages, 14 figures, ApJ, in press. The complete catalog is available in a machine-readable format via "Other formats" (source)