Variabilities Driven by Satellite Black Hole Migration in Active Galactic Nucleus 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 comoving 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 ∼10 2 –10 3 M ⊙ sBH in the inner regions of the disk surrounding a supermassive black hole with ∼10 7 M ⊙ , the reconnection process that occurred in the space outside of the disk should produce X-ray emission, which can last ∼10 3 –10 6 s with the luminosity ∼10 38 –10 42 erg s −1 .