X rays from old open clusters: M 67 and NGC 188
Astrophysics
2007-05-23 v1
Abstract
We have observed the old open clusters M 67 and NGC 188 with the ROSAT PSPC. In M 67 we detect a variety of X-ray sources. The X-ray emission by a cataclysmic variable, a single hot white dwarf, two contact binaries, and some RS CVn systems is as expected. The X-ray emission by two binaries located below the subgiant branch in the Hertzsprung Russell diagram of the cluster, by a circular binary with a cool white dwarf, and by two eccentric binaries with orbital period > 700 d is puzzling. Two members of NGC 188 are detected, including the FK Com type star D719. Another possible FK Com type star, probably not a member of NGC 188, is also detected.
Cite
@article{arxiv.astro-ph/9808329,
title = {X rays from old open clusters: M 67 and NGC 188},
author = {T. Belloni and F. Verbunt and R. D. Mathieu},
journal= {arXiv preprint arXiv:astro-ph/9808329},
year = {2007}
}
Comments
10 pages, 5 figures. Accepted for publication on Astronomy & Astrophysics