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We present detailed analysis of three globular cluster X-ray sources in theXMM-Newton extended survey of M31. The X-ray counterpart to the M31 globularcluster Bo 45 (XBo 45) was observed with XMM-Newton on 2006 December 26. Itscombined pn+MOS 0.3--10 keV lightcurve exhibited a r.m.s variability of ~10%,and its 0.3--7.0 keV emission spectrum was well described by an absorbed powerlaw with photon index 1.44$\pm$0.12. Its variability and emission ischaracteristic of low mass X-ray binaries (LMXBs) in the low-hard state,whether the accretor is a neutron star or black hole. Such behaviour istypically observed at luminosities $\la$10% Eddington. However, XBo 45exhibited this behaviour at an unabsorbed, 0.3--10 keV luminosity of2.5$\pm0.2\times 10^{38}$ erg s$^{-1}$, or{~140%} Eddington for a 1.4$M_{\odot}$ neutron star accreting hydrogen. Hence, we identify XBo 45 as a newcandidate black hole LMXB. XBo 45 appears to have been consistently bright for~30 years, consistent with theoretical prediction for a globular cluster blackhole binary formed via tidal capture. Bo 375 was observed in the 2007, January2 XMM-Newton observation, and has a two-component spectrum that is typical fora bright neutron star LMXB. Bo 135 was observed in the same field as Bo 45, andcould contain either a black hole or neutron star.

New XMM-Newton analysis of three bright X-ray sources in M31 globular clusters, including a new black hole candidate