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

Mark J. Burke, Somak Raychaudhury, Ralph P. Kraft, Nicola J. Brassington, Martin J. Hardcastle, Joanna L. Goodger, Gregory R. Sivakoff, William R. Forman, Christine Jones, Kristin A. Woodley, Stephen S. Murray, Jouni Kainulainen, Mark Birkinshaw, Judith H. Croston, Daniel A. Evans, Marat Gilfanov, Andrés Jordán, Craig L. Sarazin, Rasmus Voss, Diana M. WorrallZhongli Zhang

Research output: Contribution to journalArticlepeer-review

4 Scopus citations


We report the discovery of a bright X-ray transient CXOU J132527.6-430023 in the nearby early-type galaxy NGC5128. The source was first detected over the course of five Chandra observations in 2007, reaching an unabsorbed outburst luminosity of (1-2) × 1038ergs-1 in the 0.5-7.0keV 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.

Original languageEnglish
Article number112
JournalAstrophysical Journal
Issue number2
StatePublished - 20 Apr 2012
Externally publishedYes


  • X-rays: binaries
  • X-rays: galaxies
  • galaxies: elliptical and lenticular, cD
  • galaxies: individual (Centaurus A, NGC 5128)


Dive into the research topics of 'A transient sub-Eddington black hole X-ray binary candidate in the dust lanes of Centaurus A'. Together they form a unique fingerprint.

Cite this