Transient LoBALs at high velocities: A Case of Extreme Broad Absorption Line Variability in J115636.82+085628.9

Abstract

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.

13 pages, 6 figures, Accepted for publication in ApJ

References in corpus (16)

• The Astropy Project: Sustaining and Growing a Community-oriented Open-source Project and the Latest Major Release (v5.0) of the Core Package
• The Zwicky Transient Facility: System Overview, Performance, and First Results
• The Sloan Digital Sky Survey Quasar Catalog: Sixteenth Data Release
• The Zwicky Transient Facility: Surveys and Scheduler
• A fast and long-lived outflow from the supermassive black hole in NGC 5548
• Quasar Broad Absorption Line Variability on Multi-Year Time Scales
• Anatomy of the AGN in NGC 5548: II. The Spatial, Temporal and Physical Nature of the Outflow from HST/COS Observations
• The Sloan Digital Sky Survey Reverberation Mapping Project: Rapid CIV Broad Absorption Line Variability
• The Dependence of C IV Broad Absorption Line Properties on Accompanying Si IV and Al III Absorption: Relating Quasar-Wind Ionization Levels, Kinematics, and Column Densities
• Variability of Low-ionization Broad Absorption Line Quasars Based on Multi-epoch Spectra from The Sloan Digital Sky Survey
• Ionization driven intrinsic absorption line variability of BAL quasars in the Stripe 82 region
• 10-Year Transformation of the Obscuring Wind in NGC 5548
• Appearance vs Disappearance of broad absorption line troughs in quasars
• [OIII] emission in z=2 quasars with and without Broad Absorption Lines
• Velocity shift of Mg II and Al III broad absorption lines in quasar SDSS J134444.33+315007.6
• Time variability of ultra-fast BAL outflows using SALT: C IV equivalent width analysis