Fallback Rates from Partial Tidal Disruption Events

TL;DR

This paper confirms through hydrodynamical simulations that partial tidal disruption events exhibit a fallback rate decay following a $t^{-9/4}$ power law, enhancing understanding of TDE observational signatures.

Contribution

The study verifies the $t^{-9/4}$ fallback rate scaling in partial TDEs and introduces a method to measure the transition timescale based on impact parameter and core mass.

Findings

Confirmed the $t^{-9/4}$ fallback rate scaling in partial TDEs.

Defined and measured the break timescale for fallback rate transition.

Provided insights for interpreting TDE data from surveys.

Abstract

A tidal disruption event (TDE) occurs when a star plunges through a supermassive black hole's tidal radius, at which point the star's self-gravity is overwhelmed by the tidal gravity of the black hole. In a partial TDE, where the star does not reach the full disruption radius, only a fraction of the star's mass is tidally stripped while the rest remains intact in the form of a surviving core. Analytical arguments have recently suggested that the temporal scaling of the fallback rate of debris to the black hole asymptotes to $t^{-9/4}$ for partial disruptions, effectively independently of the mass of the intact core. We present hydrodynamical simulations that verify the existence of this predicted, $t^{-9/4}$ scaling. We also define a break timescale -- the time at which the fallback rate transitions from a $t^{-5/3}$ scaling to the characteristic $t^{-9/4}$ scaling -- and measure this break timescale as a function of the impact parameter and the surviving core mass. These results deepen our understanding of the properties and breadth of possible fallback curves expected from TDEs and will therefore facilitate more accurate interpretation of data from wide-field surveys.