• DOI:10.1088/0004-637X/749/2/112
• Corpus ID: 49949444

A transient sub-Eddington black hole X-ray binary candidate in the dust lanes of Centaurus A

@article{Burke2012ATS,
  title={A transient sub-Eddington black hole X-ray binary candidate in the dust lanes of Centaurus A},
  author={Mark J. Burke and Somak Raychaudhury and Ralph P. Kraft and Nicola J. Brassington and Martin J. Hardcastle and Joanna L Goodger and Gregory R. Sivakoff and William R. Forman and Christine Jones and Kristin A. Woodley and Stephen S. Murray and Jouni Kainulainen and Mark Birkinshaw and Judith H. Croston and Daniel A. Evans and Marat Gilfanov and Andr{\'e}s Jord{\'a}n and Craig L. Sarazin and Rasmus Voss and Diana M. Worrall and Zhongli Zhang},
  journal={The Astrophysical Journal},
  year={2012},
  volume={749},
  pages={112}
}

• M. Burke, Somak Raychaudhury, +18 authors Zhongli Zhang
• Published 14 February 2012
• Physics
• The Astrophysical Journal

We report the discovery of a bright X-ray transient CXOU J132527.6–430023 in the nearby early-type galaxy NGC 5128. The source was first detected over the course of five Chandra observations in 2007, reaching an unabsorbed outburst luminosity of (1-2) × 1038 erg s–1 in the 0.5-7.0 keV band before returning to quiescence. Such luminosities are possible for both stellar-mass black hole and neutron star (NS) X-ray binary transients. Here, we attempt to characterize the nature of the compact object. No counterpart has been detected in the optical or radio sky, but the proximity of the source to the dust lanes allows for the possibility of an obscured companion. The brightness of the source after a >100-fold increase in X-ray flux makes it either the first confirmed transient non-ultraluminous X-ray black hole system in outburst to be subject to detailed spectral modeling outside the Local Group, or a bright (>1038 erg s–1) transient NS X-ray binary, which are very rare. Such a large increase in flux would appear to lend weight to the view that this is a black hole transient. X-ray spectral fitting of an absorbed power law yielded unphysical photon indices, while the parameters of the best-fit absorbed disk blackbody model are typical of an accreting ~10 M ☉ black hole in the thermally dominant state.