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S. Trudolyubov (IGPP, University of California, Riverside), W. Priedhorsky (Los Alamos National Laboratory)
We present the results of M31 globular cluster (GC) X-ray source survey, based on the data of XMM-Newton and Chandra observations covering ~6100 arcmin2 of M31. We detected 43 globular cluster candidate sources with X-ray luminosities between ~1035 and ~1039 ergs s-1. The spectral properties and variability of M31 GC X-ray sources are consistent with that derived for the low-mass X-ray binaries (LMXB) in the bulges of M31 and the Milky Way galaxy. The X-ray luminosity function of GC sources is found to be significantly different from that of the point sources in the bulge and disk of M31 and that of the Galactic GC sources. The contribution of the GC sources to the total number of bright sources found in M31 is much higher than in the Milky Way galaxy, but surprisingly close to that of the early-type galaxies. The brightest M31 GC sources tend to reside at large galactocentric distances outside the central bulge. We found that globular clusters hosting bright X-ray sources are optically brighter and more metal rich than the rest of M31 globular clusters. The brightest sources with luminosities above 1038 ergs s-1 show tendency to reside in more metal poor clusters.
The remarkable similarities between the properties of the M31 GC X-ray sources and that of the Galactic neutron star LMXBs allow us expect most of the persistent M31 GC X-ray sources to be LMXB systems with neutron star primaries. However, the current X-ray spectral and timing data can not rule out the possibility of finding an active accreting black holes in our GC source sample.
This work was supported in part by NASA grant NAG5-12390.
The author(s) of this abstract have provided an email address for comments about the abstract: sergeyt@citrus.ucr.edu
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Bulletin of the American Astronomical Society, 36 #2
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