Variability of Mini-BAL and BAL Outflows in Quasars

TL;DR

This study investigates the variability of high-velocity mini-BAL and BAL outflows in quasars, revealing that over half of observed quasars show variability in their absorption lines, which often change in strength but not velocity, indicating shared physical origins.

Contribution

First systematic analysis of mini-BAL and high-velocity outflow variability in SDSS quasars, including the discovery of mini-BAL to BAL transitions and lack of acceleration evidence.

Findings

57% of quasars with outflows show variability over 0.9-3.3 years

Mini-BALs can transform into BALs, indicating similar nature

Variability occurs in line strength, not velocity, with no acceleration detected

Abstract

We report the results of several programs to study the variability of high-velocity (up to 0.2c) mini-"broad absorption lines" (mini-BALs) and BALs in quasar spectra, and thus to better characterize the structural and physical properties of these outflows. After the report of a highly variable mini-BAL outflow at a speed of ~0.17c in the quasar PG0935+417, we created the first systematic accounting of outflows in Sloan Digital Sky Survey (SDSS) quasar spectra that includes mini-BALs and extremely high velocity outflows (up to 0.2c) to measure their frequency. Following this study, we began a monitoring campaign to study the location, and dynamical and evolutionary effects of these outflows. This program covers a range of 0.9-3.3 years in the quasars' rest-frame by comparing new spectra (using facilities at the Kitt Peak National Observatory and MDM Observatory) with archival SDSS spectra. We find that ~57% of quasars with mini-BALs and BALs varied between just two observations. This variability tends to occur in complex ways; however, all the variable lines vary in intensity and not in velocity, not finding evidence for acceleration/deceleration in these outflows. Due to the variations in strength, mini-BALs can become BALs and vice versa, suggesting they share a similar nature. We include as an example the discovery of the transition of a mini-BAL into a BAL in the spectra of the SDSS quasar J115122+020426.