Hydrodynamic Simulations of Tidal Disruption Encores

TL;DR

This paper uses hydrodynamic simulations to study Tidal Disruption Encores in nuclear star clusters, revealing how their morphology affects luminosity and lightcurves, and aiding observational understanding of black hole environments.

Contribution

It introduces detailed hydrodynamic models of TDEEs, clarifying how disruption geometry influences debris morphology and resulting luminosity profiles.

Findings

Two distinct morphological outcomes identified: ring encores and direct encores.

Luminosities range from 10^{40} to 10^{42} erg/s, with characteristic lightcurves.

Simulations improve predictions of TDEE lightcurves and aid in probing NSC dynamics.

Abstract

We present hydrodynamic simulations with the moving-mesh code AREPO of Tidal Disruption Encores (TDEEs) in nuclear star clusters (NSCs). TDEEs arise when a stellar-mass black hole (sBH) disrupts a star within the NSC, producing debris that is unbound from the sBH but remains gravitationally bound to the central massive black hole (MBH), leading to a delayed secondary flare. We find that the morphology and thermodynamics of the fallback material depend sensitively on the disruption geometry, MBH mass, and sBH-MBH separation. We identify two distinct morphological outcomes: ring encores, where debris circularize into a torus, and direct encores, where streams plunge toward the MBH, with encore luminosities peaking at times corresponding to the freefall timescale and one orbital period, respectively. Across all simulated cases, we find these events exhibit luminosities of $10^{40}-10^{42}$ erg/s with lightcurves characteristic of their morphology. Our work greatly improves the predictions of TDEE lightcurves and empowers observations to probe into NSC dynamics and sBH population while providing possible explanations for anomalous TDE-like flares.