2012/11/26 by Maureen van den Berg, Berg, Maureen van den
Physics and Astronomy · #FOS: Physical sciences #High Energy Astrophysical Phenomena (astro-ph.HE) #Solar and Stellar Astrophysics (astro-ph.SR) #astro-ph.HE #astro-ph.SR
paper · pdf · doi:10.48550/arxiv.1211.6133
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)
arxiv created 2012/11/26 · arxiv updated 2012/11/28
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.