Ultraluminous x-ray source populations in normal galaxies: a preliminary survey with Chandra

Philip Humphrey, G Fabbiano, M Elvis, Michael Church, Monika Balucinska-Church

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33 Citations (Scopus)


We present results of a Chandra survey of the ultraluminous X-ray sources (ULX) in 13 normal galaxies, in which we combine source detection with X-ray flux measurement. 22 ULX were detected, i.e. with L-x > 1 x 10(39) erg s(-1) (L-10) and 39 other sources were detected with L-x > 5 x 10(38) erg s(-1) (L-5). We also use radial intensity profiles to remove extended sources from the sample. The majority of sources are not extended, which for a typical distance constrains the emission region size to less than 50 pc. X-ray colour-colour diagrams and spectral fitting results were examined for indicators of the ULX nature. In the case of the brighter sources, spectral fitting generally requires two-component models. In only a few cases do colour-colour diagrams or spectral fitting provide evidence of a black hole nature. We find no evidence of a correlation with stellar mass, however, there is a strong correlation with star formation as indicated by the 60-mum flux as found in previous studies.
Original languageEnglish
Pages (from-to)134-148
Number of pages15
JournalRoyal Astronomical Society. Monthly Notices
Publication statusPublished - 1 Sept 2003


  • X-rays : galaxies
  • black hole physics
  • binaries : close
  • X-rays : stars
  • accretion, accretion discs


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