The correlated variations of C IV narrow absorption lines and quasar continuum

TL;DR

This study analyzes the variability of C IV narrow absorption lines in quasars, revealing correlations with continuum changes and identifying rapid, high-velocity variations over timescales from days to years.

Contribution

It provides the first extensive analysis of C IV narrow absorption line variability in quasars with multiple observations, highlighting correlations with continuum changes and high-velocity phenomena.

Findings

19 out of 328 C IV systems showed significant variability.

High-velocity systems (>0.1c) are present among variable absorbers.

Large variations are rare on short timescales.

Abstract

We assemble 207 variable quasars from the Sloan Digital Sky Survey, all with at least 3 observations, to analyze C IV narrow absorption doublets, and obtain 328 C IV narrow absorption line systems. We find that 19 out of 328 C IV narrow absorption line systems were changed by $\mid\Delta W_r^{\lambda1548}\mid\ge3\sigma_{\Delta W_r^{\lambda1548}}$ on timescales from 15.9 to 1477 days at rest-frame. Among the 19 obviously variable C IV systems, we find that (1) 14 systems have relative velocities $\upsilon_r>0.01c$ and 4 systems have $\upsilon_r>0.1c$, where $c$ is the speed of light; (2) 13 systems are accompanied by other variable C IV systems; (3) 9 systems were changed continuously during multiple observations; and (4) 1 system with $\upsilon_{\rm r}=16~862$ km/s was enhanced by $\Delta W_r^{\lambda1548}=2.7\sigma_{\Delta W_r^{\lambda1548}}$ in 0.67 day at rest-frame. The variations of absorption lines are inversely correlated with the changes in the ionizing continuum. We also find that large variations of C IV narrow absorption lines are difficult to form on a short timescale.