First observations of the second-brightest quasar

K. M. Leighly, J. P. Halpern, D. J. Helfand, R. H. Becker, C. D. Impey

Research output: Contribution to journalArticlepeer-review

20 Scopus citations


We report the discovery of a new bright quasar, PHL 1811, as part of a follow-up program to identify bright quasars in the FIRST radio survey. With B = 13.9, R = 13.9, and z = 0.192, this quasar is now the second-brightest quasar (in apparent magnitude) known beyond z = 0.1. Optically classified as a narrow-line Seyfert 1 galaxy (NLS1), PHL 1811 is unusual for an object in this class in that it was not detected in X-rays in the ROSAT All-Sky Survey or in any previous X-ray survey. A follow-up BeppoSAX observation confirms that it is deficient in X-rays compared with other quasars, but poor signal-to-noise ratio prevents a definitive characterization of the X-ray spectrum. We consider three alternative hypotheses to explain why PHL 1811 is a weak X-ray source: (1) it is a broad absorption line quasi-stellar object and suffers X-ray absorption; (2) like several other luminous NLS1s, it exhibits high-amplitude X-ray variability and has been observed only when it is in an X-ray-quiescent state; and (3) it is intrinsically weak because it simply lacks an X-ray-emitting region.

Original languageEnglish (US)
Pages (from-to)2889-2894
Number of pages6
JournalAstronomical Journal
Issue number6
StatePublished - Jun 2001


  • Galaxies: active
  • Quasars: individual (PHL 1811)
  • X-rays

ASJC Scopus subject areas

  • Astronomy and Astrophysics
  • Space and Planetary Science


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