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, Andres Jordan, Craig L. Sarazin, Rasmus Voss, Diana M. WorrallZhongli Zhang

*Corresponding author for this work

Research output: Contribution to journalArticle (Academic Journal)peer-review

3 Citations (Scopus)

Abstract

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) x 10(38) 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 (> 10(38) 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 similar to 10 M-circle dot black hole in the thermally dominant state.

Original languageEnglish
Article number112
Number of pages8
JournalAstrophysical Journal
Volume749
Issue number2
DOIs
Publication statusPublished - Apr 2012

Keywords

  • galaxies: elliptical and lenticular, cD
  • galaxies: individual (Centaurus A, NGC 5128)
  • X-rays: binaries
  • X-rays: galaxies
  • NGC 5128 CENTAURUS
  • CHANDRA MONITORING OBSERVATIONS
  • GLOBULAR-CLUSTER
  • PARTICLE-ACCELERATION
  • XTE J1701-462
  • LUMINOUS LMXBS
  • POINT SOURCES
  • CIRCINUS X-1
  • A NGC-5128
  • MASS

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