1999/01/14 by Frank Verbunt, Verbunt, Frank
Physics and Astronomy · #Astrophysics (astro-ph) #FOS: Physical sciences #astro-ph
paper · pdf · doi:10.48550/arxiv.astro-ph/9901182
8 pages, 9 figures, to appear in "Highlights in X-ray Astronomy", proceedings of the workshop in honour of Joachim Truemper's 65th birthday, June 1998, Garching
arxiv created 1999/01/14 · arxiv updated 2009/12/01
Two new bright X-ray sources in globular clusters, and many less luminous ones in globular clusters and in old open clusters, have been discovered with ROSAT. Accurate positions obtained with ROSAT help identification with optical objects, which however is still very incomplete in globular clusters. One dim globular cluster source has been identified with a recycled radio pulsar; several others may be cataclysmic variables. The four brightest X-ray sources identified in the old open cluster M67 are puzzling, as we do not understand why they emit X-rays. In comparison with the two old open clusters studied so far, globular clusters are remarkably underluminous in X-rays.