X-ray sources in Galactic old open star clusters
Abstract
I review the current status of studies of the X-ray sources in Galactic old open clusters. Cataclysmic variables (CVs), magnetically-active binaries (ABs), and sub-subgiants (SSGs) dominate the X-ray emission of old open clusters. Surprisingly, the number of ABs detected inside the half-mass radius with Lx >~ 1e30 erg/s (0.3-7 keV) does not appear to scale with cluster mass. Comparison of the numbers of CVs, ABs, and SSGs per unit mass in old open and globular clusters shows that each of these classes is under-abundant in globulars. This suggests that dense environments suppress the frequency of even some of the hardest binaries.
Cite
@article{arxiv.1211.6133,
title = {X-ray sources in Galactic old open star clusters},
author = {Maureen van den Berg},
journal= {arXiv preprint arXiv:1211.6133},
year = {2012}
}
Comments
11 pages, 2 figures, to appear in the proceedings of the meeting "370 years of astronomy in Utrecht", Noordwijkerhout, The Netherlands, April 2-5, 2012 (ASP Conference Series)