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| Main Authors: | , , , , |
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| Format: | Preprint |
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2025
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| Online Access: | https://arxiv.org/abs/2508.01029 |
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| _version_ | 1866918111801769984 |
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| author | Aromal, P. Srianand, R. Gallagher, S. C. Vivek, M. Petitjean, P. |
| author_facet | Aromal, P. Srianand, R. Gallagher, S. C. Vivek, M. Petitjean, P. |
| contents | We present a multi-epoch spectroscopic study of the broad absorption line (BAL) quasar J115636.82+085628.9 (z(em) = 2.1077), based on five spectra spanning nearly two decades in the observer's frame. This source exhibits remarkable variability in both low-ionization (LoBAL: Al III and Mg II) and high-ionization (HiBAL: C IV and Si IV) absorption features. For the first time, we detect the emergence and subsequent disappearance of LoBAL troughs at high velocities (~20,000 kms$^{-1}$), coinciding with the strengthening and weakening of the corresponding HiBAL absorption. The C IV BAL profile extends from ~6,700 kms$^{-1}$ to a conservative upper limit of 30,000 kms$^{-1}$ and is composed of narrow, variable absorption features embedded within a broad, smooth envelope. Both C IV and Si IV BAL troughs exhibit dramatic equivalent width (EW) changes, among the most extreme reported to date. Notably, these EW variations are strongly anti-correlated with continuum flux changes inferred from optical photometric light curves. We interpret this variability as the result of a new absorbing flow transiting into our line of sight, increasing the shielding of a more distant, pre-existing outflow and giving rise to transient LoBAL absorption. This scenario supports a unified picture in which LoBAL and HiBAL features arise from similar outflow structures, with observed differences governed primarily by line-of-sight column densities consistent with previous findings. |
| format | Preprint |
| id |
arxiv_https___arxiv_org_abs_2508_01029 |
| institution | arXiv |
| publishDate | 2025 |
| record_format | arxiv |
| spellingShingle | Transient LoBALs at high velocities: A Case of Extreme Broad Absorption Line Variability in J115636.82+085628.9 Aromal, P. Srianand, R. Gallagher, S. C. Vivek, M. Petitjean, P. Astrophysics of Galaxies We present a multi-epoch spectroscopic study of the broad absorption line (BAL) quasar J115636.82+085628.9 (z(em) = 2.1077), based on five spectra spanning nearly two decades in the observer's frame. This source exhibits remarkable variability in both low-ionization (LoBAL: Al III and Mg II) and high-ionization (HiBAL: C IV and Si IV) absorption features. For the first time, we detect the emergence and subsequent disappearance of LoBAL troughs at high velocities (~20,000 kms$^{-1}$), coinciding with the strengthening and weakening of the corresponding HiBAL absorption. The C IV BAL profile extends from ~6,700 kms$^{-1}$ to a conservative upper limit of 30,000 kms$^{-1}$ and is composed of narrow, variable absorption features embedded within a broad, smooth envelope. Both C IV and Si IV BAL troughs exhibit dramatic equivalent width (EW) changes, among the most extreme reported to date. Notably, these EW variations are strongly anti-correlated with continuum flux changes inferred from optical photometric light curves. We interpret this variability as the result of a new absorbing flow transiting into our line of sight, increasing the shielding of a more distant, pre-existing outflow and giving rise to transient LoBAL absorption. This scenario supports a unified picture in which LoBAL and HiBAL features arise from similar outflow structures, with observed differences governed primarily by line-of-sight column densities consistent with previous findings. |
| title | Transient LoBALs at high velocities: A Case of Extreme Broad Absorption Line Variability in J115636.82+085628.9 |
| topic | Astrophysics of Galaxies |
| url | https://arxiv.org/abs/2508.01029 |