Barnard, R.; Stiele, H.; Hatzidimitriou, D.; Kong, A. K. H.; Williams, B. F.; Pietsch, W.; Kolb, U. C.; Haberl, F. and Sala, G.
|DOI (Digital Object Identifier) Link:||http://dx.doi.org/10.1086/592594|
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We present a detailed analysis of three globular cluster X-ray sources in the XMM-Newton extended survey of M31. The X-ray counterpart to the M31 globular cluster Bo 45 (XBo 45) was observed with XMM-Newton on 2006 December 26. Its combined pn+MOS 0.3–10 keV light curve was seen to vary by 10%, and its 0.3–7.0 keV emission spectrum was well described by an absorbed power law with photon index . Its variability and emission is characteristic of low-mass X-ray binaries (LMXBs) in the low-hard state, whether the accretor is a neutron star or black hole. Such behavior is typically observed at luminosities 10% Eddington. However, XBo 45 exhibited this behavior at an unabsorbed, 0.3–10 keV luminosity of erg s−1, or 140% Eddington for a 1.4 neutron star accreting hydrogen. Hence, we identify XBo 45 as a new candidate black hole LMXB. XBo 45 appears to have been consistently bright for 30 years, consistent with theoretical prediction for a globular cluster black hole binary formed via tidal capture. Bo 375 was observed in the 2007 January 2 XMM-Newton observation, and has a two-component spectrum that is typical for a bright neutron star LMXB. Bo 135 was observed in the same field as Bo 45, and could contain either a black hole or a neutron star.
|Item Type:||Journal Article|
|Copyright Holders:||2008 The American Astronomical Society|
|Academic Unit/Department:||Science > Physical Sciences
|Interdisciplinary Research Centre:||Centre for Earth, Planetary, Space and Astronomical Research (CEPSAR)|
|Depositing User:||Robin Barnard|
|Date Deposited:||08 Jan 2009 01:28|
|Last Modified:||14 Jan 2016 17:34|
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