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

Ning Xiao Zhang, W. N. Brandt, N. S. Ahmed, P. B. Hall, B. Luo, Scott F. Anderson, N. Filiz Ak, P. Petitjean, D. P. Schneider, Yue Shen, R. Srianand

Research output: Contribution to journalArticlepeer-review


We present Chandra observations of seven broad absorption line (BAL) quasars at z = 0.8632.516 with redshifted BAL troughs (RSBALs). Five of our seven targets were detected by Chandra in 4-13 ks exposures with ACIS-S. The αox values, Δ αoxvalues, 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 Γeff = 0.5+0.5 -0.4. These findings support the presence of heavy X-ray absorption (NH ≈ 2 × 1023 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.

Original languageEnglish (US)
Article number101
JournalAstrophysical Journal
Issue number2
StatePublished - Apr 20 2017


  • X-rays: galaxies
  • accretion, accretion disks
  • galaxies: nuclei
  • quasars: absorption lines
  • quasars: general

ASJC Scopus subject areas

  • Astronomy and Astrophysics
  • Space and Planetary Science


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