Keck observations of ROSAT ultra-luminous X-ray source candidates

Diane Sonya Wong*, Ryan Chornock, Alexei V. Filippenko

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

1 Scopus citations


We present results of optical follow-up observations of candidate ultra-luminous X-ray sources (ULXs). Using Keck optical spectroscopy, 17 of the candidates from the Colbert and Ptak [Colbert, E.J.M., Ptak, A.F. A catalog of candidate intermediate-luminosity X-ray objects. ApJS 143, 25-45, 2002] catalog have been identified; this is one of the largest sets of optical identifications of such objects thus far. Fifteen are background active galactic nuclei (AGN); two are foreground stars in our Galaxy. These findings are consistent with background and foreground object expectations, as derived from log N-log S relations. Also, the results are briefly discussed in terms of the spiral-galaxy/ULX connection.

Original languageEnglish (US)
Pages (from-to)2813-2815
Number of pages3
JournalAdvances in Space Research
Issue number12
StatePublished - 2006


  • Black hole physics
  • Catalogs
  • Galaxies
  • Quasars
  • X-rays
  • distances and redshifts
  • galaxies
  • general
  • individual (NGC 720, NGC 1316, NGC 1365, NGC 1399, NGC 2775, NGC 3226, IC 2597, NGC 3923, NGC 4151, NGC 4373, NGC 5128)

ASJC Scopus subject areas

  • Aerospace Engineering
  • Astronomy and Astrophysics
  • Geophysics
  • Atmospheric Science
  • Space and Planetary Science
  • Earth and Planetary Sciences(all)


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