Chandra X-Ray Sources in the Collapsed-Core Globular Cluster M30 (NGC 7099)
Abstract
We report the detection of six discrete, low-luminosity (LX<1033 ergs s-1) X-ray sources, located within 12" of the center of the collapsed-core globular cluster M30 (NGC 7099), and a total of 13 sources within the half-mass radius, from a 50 ks Chandra ACIS-S exposure. Three sources lie within the very small upper limit of 1.9" on the core radius. The brightest of the three core sources has a luminosity of LX(0.5-6 keV)~6×1032 ergs s-1 and a blackbody-like soft X-ray spectrum, which are both consistent with it being a quiescent low-mass X-ray binary (qLMXB). We have identified optical counterparts to four of the six central sources and a number of the outlying sources, using deep Hubble Space Telescope and ground-based imaging. While the two proposed counterparts that lie within the core may represent chance superpositions, the two identified central sources that lie outside of the core have X-ray and optical properties consistent with being cataclysmic variables (CVs). Two additional sources outside of the core have possible active binary counterparts. We discuss the X-ray source population of M30 in light of its collapsed-core status.
- Publication:
-
The Astrophysical Journal
- Pub Date:
- March 2007
- DOI:
- 10.1086/507572
- arXiv:
- arXiv:astro-ph/0606382
- Bibcode:
- 2007ApJ...657..286L
- Keywords:
-
- Galaxy: Globular Clusters: Individual: Messier Number: M30;
- Galaxy: Globular Clusters: Individual: NGC Number: NGC 7099;
- Stars: Novae;
- Cataclysmic Variables;
- Stars: Neutron;
- X-Rays: Binaries;
- Astrophysics
- E-Print:
- 18 pages, 13 figures (8 color), resubmitted to ApJ after incorporating referee comments