X-ray and multi-epoch optical/UV investigations of BAL to non-BAL quasar transformations

• Published in: arXiv.org 2018-10
• Main Authors: Sameer, Brandt, W N, Anderson, S, Hall, P B, Vivek, M, N Filiz Ak, Grier, C J, Ahmed, N S, Luo, B, Myers, A D, P Rodríguez Hidalgo, Ruan, J, Schneider, D P
• Format: Article
• Language: English
• Subjects: Absorption; Line of sight; Quasars; Shielding; Telescopes; X ray spectra
• ISSN: 2331-8422
• DOI: 10.48550/arxiv.1810.03625

We report on an X-ray and optical/UV study of eight Broad Absorption Line (BAL) to non-BAL transforming quasars at \(z\,\approx\,\)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 their values of \(\alpha_{\rm ox}\) and \(\Delta{\alpha}_{\rm ox}\), 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 \(\Gamma_{\rm eff}\,=\,1.69^{+0.25}_{-0.25}\). 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).