2001/03/01 by Karen M. Leighly, K. M. Leighly, J. P. Halpern +3 · 2 citations
Physics and Astronomy · #Astrophysical Phenomena and Observations #Astrophysics and Cosmic Phenomena #Galaxies: Formation, Evolution, Phenomena #astro-ph
paper · pdf · doi:10.1086/321094
15 pages including 5 figures; accepted for publication in the AJ (June 2001)
arxiv created 2001/03/01 · openalex publication_date 2001/06/01 · arxiv updated 2009/12/01 · openalex created_date 2025/10/10 · openalex updated_date 2026/07/31
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.