Barnard, R.; Stiele, H.; Hatzidimitriou, D.; Kong, A. K. H.; Williams, B. F.; Pietsch, W.; Kolb, U. C.; Haberl, F. and Sala, G.
(2008).
| DOI (Digital Object Identifier) Link: | http://dx.doi.org/doi:10.1086/592594 |
|---|---|
| Google Scholar: | Look up in Google Scholar |
Abstract
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 |
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| Copyright Holders: | 2008 The American Astronomical Society |
| ISSN: | 0004-637X |
| Academic Unit/Department: | ?? scie-phya ?? Science > Physical Sciences |
| Interdisciplinary Research Centre: | Centre for Earth, Planetary, Space and Astronomical Research (CEPSAR) |
| Item ID: | 12792 |
| Depositing User: | Robin Barnard |
| Date Deposited: | 08 Jan 2009 01:28 |
| Last Modified: | 16 Nov 2012 16:36 |
| URI: | http://oro.open.ac.uk/id/eprint/12792 |
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