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

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 $\mid \Delta W_r^{\lambda 1548}\mid \ge 3{\sigma }_{\Delta W_r^{\lambda 1548}}$ 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 ${\upsilon }_{\mathrm{r}}=16862$ km/s was enhanced by $\Delta W_r^{\lambda 1548}=2.7{\sigma }_{\Delta W_r^{\lambda 1548}}$ 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.

9 pages, 6figures