@article{b7746b16a67b4ed7932b187364f10cc0,
title = "X-ray and multi-epoch optical/UV investigations of BAL to non-BAL quasar transformations",
abstract = "We report on an X-ray and optical/ultraviolet (UV) study of eight broad absorption line (BAL) to non-BAL transforming quasars at z ≈ 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 3.5m telescopes. New Chandra observations obtained for these objects show that their values of αox and Δαox, 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 Γeff = 1.69-0.25+0.25. The newer Gemini and ARC 3.5m 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).",
author = "Sameer and Brandt, {W. N.} and S. Anderson and Hall, {P. B.} and M. Vivek and {Filiz Ak}, N. and Grier, {C. J.} and Ahmed, {N. S.} and B. Luo and Myers, {A. D.} and Hidalgo, {P. Rodr{\'i}guez} and J. Ruan and Schneider, {D. P.}",
note = "Funding Information: We thank the anonymous referee for his/her suggestions which helped improve the manuscript. We acknowledge helpful discussions with Chien-Ting Chen, Eric Feigelson, Sean McGraw, Qin-gling Ni, Yue Shen, Fabio Vito, Guang Yang, Weimin Yi, Ning-Xiao Zhang, and Shifu Zhu. S and WNB acknowledges support from NSF grant AST-1516784 and Chandra X-ray Center grant GO5-16089X. NFA acknowledges support from TUBITAK 115F037. BL acknowledges financial support from the National Key R&D Program of China grant 2016YFA0400702 and National Natural Science Foundation of China grant 11673010. Funding Information: The expected value of αox for a typical radio-quiet quasar is calculated from the established αox–L2500{\AA} correlation given as equation (3) of J07. 2Based on observations obtained at the Gemini Observatory, which is operated by the Association of Universities for Research in Astronomy, Inc., under a cooperative agreement with the NSF on behalf of the Gemini partnership: the National Science Foundation (United States), the National Research Council (Canada), CONICYT (Chile), Ministerio de Ciencia, Tecnolog{\'i}a e Innovaci{\'o}n Productiva (Argentina), and Minist{\'e}rio da Ci{\^e}ncia, Tecnologia e Inovac¸{\~a}o (Brazil). 3Based on observations obtained with the Apache Point Observatory 3.5 m telescope, which is owned and operated by the Astrophysical Research Consortium. Publisher Copyright: {\textcopyright} 2018 The Author(s). Published by Oxford University Press on behalf of the Royal Astronomical Society.",
year = "2019",
month = jan,
day = "1",
doi = "10.1093/mnras/sty2718",
language = "English (US)",
volume = "482",
pages = "1121--1134",
journal = "Monthly Notices of the Royal Astronomical Society",
issn = "0035-8711",
publisher = "Oxford University Press",
number = "1",
}