Effects of Intrinsic Active Galactic Nucleus Variability on Optical Quasiperiodic Oscillations Related to Subparsec Binary Black Hole Systems in Broad-line Active Galactic Nuclei

Abstract

In this paper, an oversimplified model is proposed to test the effects of intrinsic active galactic nucleus (AGN) variability on expected optical quasiperiodic oscillations (QPOs) related to subparsec binary black hole systems (BBHs) in broad-line AGN. The commonly accepted continuous autoregressive process is applied to describe intrinsic AGN variability related to each BH accreting system in a subparsec BBH system. Considering obscurations related to orbital rotations with periodicity T _p , artificial light curves including signals for optical QPOs can be built. Then, comparing the intrinsic periodicities T _p with the measured robust periodicities T _o through the artificial light curves, we find distributions of T _p / T _o have four significant peaks around 1, 2, 3, and 4, leading less than half of the artificial light curves to have consistency between T _o and T _p . Moreover, different collected model parameters have few effects on the distributions of T _p / T _o , indicating the effects of intrinsic AGN variability on optical QPOs are significantly strong and stable. Furthermore, after checking properties of optical QPOs in the light curves with different time steps, we find there are tiny effects of time steps on optical QPOs.

Keywords

• Active galactic nuclei
• Supermassive black holes
• Lomb-Scargle periodogram
• Periodic orbit