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

Understanding the properties of outflows relies heavily on the variability of absorption lines in quasars, particularly BALs. While the exact cause of this variability remains uncertain, two mechanisms are generally favored: gas clouds that move across the line of sight (the TM scenario) and changes in ionizing flux (the IC scenario). Some studies have found evidence supporting the IC scenario, such as anti-correlations observed between the fractional variations of the continuum and absorption line for several BAL samples (Lu et al. 2018; Lu & Lin 2018; Vivek 2019). However, these studies have not compared the EW changes of BALs in different ionization states to their fractional variations of the continuum.