We present absorption variability results for 134 bona fide Mg II broad absorption-line (BAL) quasars at 0.46 z 2.3 covering days to ∼10 yr in the rest frame. We use multiple-epoch spectra from the Sloan Digital Sky Survey, which has delivered the largest such BAL variability sample ever studied. Mg II-BAL identifications and related measurements are compiled and presented in a catalog. We find a remarkable time-dependent asymmetry in the equivalent width (EW) variation from the sample, such that weakening troughs outnumber strengthening troughs, the first report of such a phenomenon in BAL variability. Our investigations of the sample further reveal that (i) the frequency of BAL variability is significantly lower (typically by a factor of 2) than that in high-ionization BALQSO samples, (ii) Mg II-BAL absorbers tend to have relatively high optical depths and small covering factors along our line of sight, (iii) there is no significant EW-variability correlation between Mg II troughs at different velocities in the same quasar, and (iv) the EW-variability correlation between Mg II and Al III BALs is significantly stronger than that between Mg II and C IV BALs at the same velocities. These observational results can be explained by a combined transverse-motion/ionization-change scenario, where transverse motions likely dominate the strengthening BALs while ionization changes and/or other mechanisms dominate the weakening BALs.
- Galaxies: active
- Quasars: absorption lines
- Quasars: general Supporting material: machine-readable tables
ASJC Scopus subject areas
- Astronomy and Astrophysics
- Space and Planetary Science
FingerprintDive into the research topics of 'Variability of low-ionization broad absorption-line quasars based on multi-epoch spectra from the sloan digital sky survey'. Together they form a unique fingerprint.
Yi, W. (Creator), Brandt, W. N. (Creator), Hall, P. B. (Creator), Vivek, M. (Creator), Beatty, C. (Creator), Filiz Ak, A. N. (Contributor), Schneider, D. P. (Creator), McGraw, S. M. (Creator), Vivek, M. (Creator) & Grier, C. J. (Creator), Centre de Donnees Strasbourg (CDS), 2020