Enhancement of the Rate of Tidal Disruption Events in Active Galactic Nuclei due to the Sweeping Secular Resonance Mechanism

TL;DR

This paper introduces a new mechanism called sweeping secular resonance (SSR) driven by an intermediate-mass companion and a depleting gaseous disk, which explains the observed excess of tidal disruption events (TDEs) in active galactic nuclei (AGN).

Contribution

The study presents an analytical framework and N-body simulations demonstrating how SSR enhances TDE rates, highlighting the role of IMC-to-SMBH mass ratios and disk depletion timescales.

Findings

SSR can increase TDE rates to 10^{-3}-10^{-2} per galaxy per year.

Effective for co-orbiting IMCs with specific mass ratios and disk depletion timescales.

High TDE rates may indicate the presence of hidden parsec-scale IMCs.

Abstract

Tidal disruption event (TDE) rates in active galactic nuclei (AGN) consistently exceed predictions from two-body relaxation, particularly in post-starburst and green valley galaxies. We explain this excess with a new mechanism: a sweeping secular resonance (SSR) driven by an intermediate-mass companion (IMC) and a depleting gaseous disk. As the disk mass declines, a resonance between stellar and IMC orbital precession sweeps through the nuclear cluster, exciting stellar eccentricities to near unity on orbital timescales far faster than gravitational relaxation. Our analytical framework, validated by N-body simulations (REBOUND), shows this mechanism requires IMC-to-SMBH mass ratios of $q \geq 10^{-3}$, disk mass ratio $p \geq 10^{-3}$, and few Myr-scale disk depletion. It is highly effective for co-orbiting IMCs but negligible for counter-orbiting ones. The TDE rate peaks at $10^{-3}-10^{-2}$ per galaxy per year for a depletion timescale $\tau_{\rm dep} \sim 10$ Myr. Even lower-mass IMCs can produce significant enhancements with compact, long-lived disks. Our model naturally explains elevated AGN TDE rates and implies that a high TDE incidence is a potential tracer of hidden parsec-scale IMCs, offering testable predictions for future AGN monitoring.