Published January 1, 2019
| Version v1
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X-ray and multi-epoch optical/UV investigations of BAL to non-BAL quasar transformations
Creators
- 1. Penn State Univ, Dept Astron & Astrophys, 525 Davey Lab, University Pk, PA 16802 USA
- 2. Univ Washington, Dept Astron, C319, Seattle, WA 98195 USA
- 3. York Univ, Dept Phys & Astrophys, 4700 Keele St, N York, ON M3J 1P3, Canada
- 4. Nanjing Univ, Sch Astron & Space Sci, Nanjing 210093, Jiangsu, Peoples R China
- 5. Univ Wyoming, Dept Phys & Astron, 1000 E Univ,Dept 3905, Laramie, WY 82071 USA
- 6. Humboldt State Univ, Dept Phys & Astron, 1 Harpst St, Arcata, CA 95521 USA
- 7. McGill Univ, Dept Phys, 3550 Rue Univ, Montreal, PQ H3A 2T8, Canada
Description
We report on an X-ray and optical/ultraviolet (UV) study of eight broad absorption line (BAL) to non-BAL transforming quasars at z approximate to 1.7-2.2 over 0.29-4.95 rest-frame years with at least three spectroscopic epochs for each quasar from the SDSS, BOSS, Gemini, and ARC 3.5 m telescopes. New Chandra observations obtained for these objects show that their values of alpha(ox) and Delta alpha(ox), as well as their spectral energy distributions, are consistent with those of non-BAL quasars. Moreover, our targets have X-ray spectral shapes that are, on average, consistent with weakened absorption with an effective power-law photon index of Gamma(eff) = 1.69(-0.25)(+0.25). The newer Gemini and ARC 3.5 m spectra reveal that the BAL troughs have remained absent since the BOSS observations where the BAL disappearance was discovered. The X-ray and optical/UV results in tandem are consistent with at least the X-ray-absorbing material moving out of the line of sight, leaving an X-ray-unabsorbed non-BAL quasar. The UV absorber might have become more highly ionized (in a shielding-gas scenario) or also moved out of the line of sight (in a wind-clumping scenario).
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