Abstract:

This study investigates the Catalina Sky Survey photometric light curves of 1886 quasars that show broad absorp-tion lines (BAL) in their spectra as a manifestation of the disk outflows. To describe the brightness variability strength of the quasars, we define a suitable parameter measuring the variation amplitude. The distribution of the variation amplitude parameter for our main sample is asymmetric. The asymmetry of this non-normal distribution is largely due to the contribution of the most variable quasars. To assess the relations between the variability ampli-tude and quasar physical parameters, we construct two subsets from our main sample, i.e. the most variable and the most stable (the least variable) quasars. We assess relations between the variability amplitude and the quasar pa-rameters such as redshift, apparent and absolute magnitudes, luminosity, and the mass of the central black hole. By comparing the parameter distributions of these two subsets, we show that the most variable quasars tend to be dimmer. The further correlation analysis on the entire main sample confirms the strong relationship between quasar brightness and variability. This study presents the brightness and variability relation of BAL quasars, for the first time. Since this result is consistent with the known relation of the normal quasars, we suggest that BAL quasars have no significant difference from normal quasars in terms of the photometric variability mechanisms. The significant inverse correlation between the quasar variability and brightness supports the common idea that disk instability might be the dominant mechanism behind the photometric light variations.

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