An Explanation for the Overrepresentation of Tidal Disruption Events in Post-starburst Galaxies

Abstract

Tidal disruption events (TDEs) provide a valuable probe for studying the dynamics of stars in the nuclear environments of galaxies. Recent observations show that TDEs are strongly overrepresented in post-starburst or “green valley” galaxies, although the underlying physical mechanism remains unclear. Considering the possible interaction between stars and active galactic nucleus (AGN) disks, the TDE rates can be greatly changed compared to those in quiescent galactic nuclei. In this work, we revisit TDE rates by incorporating an evolving AGN disk within the framework of “loss cone” theory. We numerically evolve the Fokker–Planck equations by considering star–disk interactions, in situ star formation in the unstable region of the outer AGN disk, and evolution of the accretion process of supermassive black holes. We find that the TDE rates are enhanced by about 2 orders of magnitude shortly after the AGN transitions into an inactive stage. During this phase, the accumulated stars rapidly scatter into the loss cone due to the disappearance of the inner standard thin disk. Our results provide an explanation for the overrepresentation of TDEs in post-starburst galaxies.