M31 GLOBULAR CLUSTER X-RAY SOURCES: XMM-NEWTON AND CHANDRA RESULTS

摘要: We present the results of an M31 globular cluster (GC) X-ray source survey, based on data XMM-Newton and Chandra observations covering ~6100 arcmin2 M31. detected 43 sources coincident with GC candidates from various optical surveys. The inferred isotropic luminosities lie between ~1035 ~1039 ergs s-1 in 0.3-10 keV energy band. spectral properties 31 brightest our sample were found to be similar those low-mass binaries (LMXBs) located bulge GCs Milky Way. distribution is consistent that derived for other nearby galaxies different morphological type. Several demonstrate a correlation level flux hardness their spectrum reminiscent Galactic Z atoll sources. ~80% multiple measurements available show significant variability timescales days years. RX J0043.2+4127, Bo 163, has been recurrent transient outbursts peak ~1038 s-1. timescale individual observations, ranging aperiodic fluctuations regular dipping. luminosity function significantly point disk ~10 times higher much fraction bright than Way distribution. Six persistent (or ~14% total number) have exceeding 1038 during all three occasionally exceed level. Our indicate make dominant contribution counts areas covered by survey: ~40% number above 1037 reside GCs, rising 67%-90% but surprisingly close early-type galaxies. tend at large galactocentric distances outside central bulge. hosting are optically brighter more metal-rich rest agreement previous studies. sources, s-1, tendency metal-poor clusters. remarkable similarities neutron star LMXBs lead us expect most LMXB systems primaries. However, current timing cannot rule out possibility finding active accreting black holes sample.