Investigating the Variability of Absorption Lines in Quasars: A Comparative Study of BALs in Different Ionization States

Understanding the properties of outflows in quasars, particularly BALs, is heavily reliant on the variability of absorption lines. Although the exact cause of this variability remains unclear, there are two commonly favored mechanisms: gas clouds moving across the line of sight (TM scenario) and changes in ionizing flux (IC scenario). While some studies have provided supporting evidence for the IC scenario, such as anti-correlations between the fractional variations of the continuum and absorption line observed in several samples of BAL (Lu et al. 2018; Lu & Lin 2018; Vivek 2019), none of these existing articles have compared the EW variations of BALs in different ionization states with their fractional variations of the continuum.