Tidal Disruption Event Demographics in Supermassive Black Hole Binaries Over Cosmic Times

TL;DR

This study uses simulations of supermassive black hole binaries to explain observed TDE rates and light curve features, providing insights into SMBH demographics and binary fractions over cosmic time.

Contribution

It introduces a simulation-based model incorporating binary effects to explain TDE rate trends and light curve anomalies, linking observations to SMBH binary presence.

Findings

Binary SMBHs show increasing TDE rates with mass, unlike single SMBHs.

TDE rates in post-starburst galaxies align with binary SMBH predictions.

Short TDE light curves suggest disruptions by less massive black holes in binaries.

Abstract

Tidal disruption events (TDEs) offer a unique probe of supermassive black hole (SMBH) demographics, but their observed rates remain difficult to reconcile with standard single-SMBH models. In this work, we use simulations of SMBH binaries, including the combined effects of eccentric Kozai-Lidov oscillations and two-body relaxation, to explore how TDE rates scale with SMBH mass and redshift. We find that binary systems exhibit increasing TDE rates with mass, in contrast to the declining trend expected for single SMBHs. These binary-driven rates match those observed in post-starburst galaxies, suggesting that a subset of TDE hosts may contain SMBH binaries. TDE light curves in some massive galaxies exhibit unexpectedly short durations, suggesting that the disrupting SMBH may be less massive than implied by host galaxy scaling relations, consistent with disruptions by the less massive black hole in a binary. By convolving our mass-dependent rates with the SMBH mass function, we predict redshift-dependent TDE rates, which we show can be used to constrain the supermassive black hole binary fraction. Our results provide a testable framework for interpreting TDE demographics in upcoming wide-field surveys such as LSST and Roman.