Variabilities driven by satellite black hole migration in AGN disks

Abstract

The physical origin of active galactic nucleus (AGN) variability remains unclear. Here we propose that the magnetic reconnection induced by the migration of satellite black holes (sBHs) in the AGN disk can be a new plausible mechanism for AGN short-term variability. During the sBH migration, the co-moving plasmas surrounding the sBH could influence the large-scale magnetic field of the AGN disk and trigger the magnetic reconnections to contribute to AGN UV/optical variability. Meanwhile, high-magnetization plasmas are more likely to escape the disk and cause a secondary magnetic reconnection in the corona. For a $\sim 10^{2}-10^{3}~{M_\mathrm{\odot}}$ sBH in the inner regions of the disk surrounding a supermassive black hole with $\sim 10^{7}~{M_\mathrm{\odot}}$, the reconnection process occurred in the space out of the disk should produce X-ray emission, which can last $\sim 10^3-10^6~\rm s$ with the luminosity $\sim 10^{38}- 10^{42}~\rm{erg ~s^{-1}}$.