X- Ray Insights into the Nature of Quasars with Redshifted Broad Absorption Lines

ZHANG N., Brandt W. N. , AHMED N. S. , Hall P. B. , LUO B., Anderson S. F. , ...More

ASTROPHYSICAL JOURNAL, vol.839, no.2, 2017 (Journal Indexed in SCI) identifier identifier

  • Publication Type: Article / Article
  • Volume: 839 Issue: 2
  • Publication Date: 2017
  • Doi Number: 10.3847/1538-4357/aa6842
  • Title of Journal : ASTROPHYSICAL JOURNAL


We present Chandra observations of seven broad absorption line (BAL) quasars at z = 0.863-2.516 with redshifted BAL troughs (RSBALs). Five of our seven targets were detected by Chandra in 4-13 ks exposures with ACIS-S. The alpha(ox) values, Delta alpha(ox) values, and spectral energy distributions of our targets demonstrate they are all X-ray weak relative to expectations for non-BAL quasars, and the degree of X-ray weakness is consistent with that of appropriately matched BAL quasars generally. Furthermore, our five detected targets show evidence for hard X-ray spectral shapes with a stacked effective power-law photon index of Gamma(eff) = 0.5(-0.4)(+0.5). These findings support the presence of heavy X-ray absorption (N-H approximate to 2 x 10(23) cm(-2)) in RSBAL quasars, likely by the shielding gas found to be common in BAL quasars more generally. We use these X-ray measurements to assess models for the nature of RSBAL quasars, finding that a rotationally dominated outflow model is favored while an infall model also remains plausible with some stipulations. The X-ray data disfavor a binary quasar model for RSBAL quasars in general.