2003/03/05 by G. Risaliti, M. Elvis, R. Gilli +1 · 3 citations
Physics and Astronomy · #Astrophysical Phenomena and Observations #Galaxies: Formation, Evolution, Phenomena #Gamma-ray bursts and supernovae #astro-ph
paper · pdf · doi:10.1086/375048
published as Astrophys.J. 587 (2003) L9-L14 · 11 Pages, 3 figures, accepted for publication in ApJ Letters
arxiv created 2003/03/05 · openalex publication_date 2003/03/25 · arxiv updated 2009/12/01 · openalex created_date 2016/06/24 · openalex updated_date 2026/07/31
We present Chandra observations of 18 spectroscopically selected quasars, which are already known to be X-ray weak from previous ROSAT observations. All the sources but one are detected by Chandra , and spectral analysis suggests that most of them are intrinsically underluminous in the X-rays (by a factor from 3 to >100). These objects could represent a large population of quasars with a spectral energy distribution different from that of standard blue quasars. We discuss the possibility that a significant fraction of the obscured active galactic nuclei needed in synthesis models of the X-ray background could instead be optical, broad-line, X-ray-weak quasars.