The phenomenon of changing-look (CL) behavior in active galactic nuclei (AGN) is characterized by dramatic changes in luminosity and/or emission line profiles over relatively short periods, ranging from months to years. The origin of CL-AGNs remains a mystery, but one proposed explanation involves the response of the inner AGN disk to tidal disruption events (TDEs) around the supermassive black hole (SMBH). In this Letter, we calculate the predicted frequency of AGN TDEs as a function of SMBH mass and compare the results to the observed CL-AGN distribution. We find that if the fraction of CL-AGNs caused by AGN-TDEs is high, then: (1) most SMBHs in CL-AGN are near maximal spin, with the dimensionless spin parameter a>0.9; (2) AGN inner disks have a high surface density (≥107gcm−2); (3) typical AGN lifetimes are ∼10-100 Myr; and (4) a nuclear star cluster initial mass function (IMF) that scales as ∼m∗−1.6 is preferred. Future observations of CL-AGN will help constrain the fraction of CL-AGNs caused by AGN-TDEs, SMBH spins, AGN lifetimes, and the nuclear star cluster IMF.
@article{arxiv.2406.12096,
title = {Conditions for Changing-Look AGNs from Accretion Disk-Induced Tidal Disruption Events},
author = {Yihan Wang and Matthew J. Graham and K. E. Saavik Ford and Barry McKernan and Taeho Ryu and Daniel Stern},
journal= {arXiv preprint arXiv:2406.12096},
year = {2024}
}