Tidal radii of main sequence stars -- III. Partial disruptions

TL;DR

This study investigates partial tidal disruption events of main-sequence stars by a supermassive black hole, revealing unique debris fallback behaviors, remnant properties, and potential for multiple disruptions.

Contribution

It provides detailed analysis of partial disruptions, including debris fallback rates, remnant characteristics, and the likelihood of subsequent tidal events, expanding understanding of stellar-black hole interactions.

Findings

Fallback rate deviates from t^{-5/3} in partial disruptions

Remnants are spun-up and hotter than typical MS stars

Remnants have low escape velocities, limiting their galactic travel

Abstract

In this paper, the third in this series, we continue our study of tidal disruption events of main-sequence stars by a non-spinning $10^{6}~\rm{M}_\odot$ supermassive black hole. Here we focus on the outcomes of partial disruptions. As the encounter becomes weaker, the debris mass is increasingly concentrated near the outer edges of the energy distribution. As a result, the mass fallback rate can deviate substantially from a $t^{-5/3}$ power-law, becoming more like a single peak with a tail declining as $t^{-p}$ with $p\simeq2-5$. Surviving remnants are spun-up in the prograde direction and are hotter than MS stars of the same mass. Their specific orbital energy is $\simeq10^{-3}\times$ that of the debris (but of either sign with respect to the black hole potential) while their specific angular momentum is close to that of the original star. Even for strong encounters, remnants have speeds at infinity relative to the black hole potential $\lesssim 300$ km s$^{-1}$, so they are unable to travel far out into the galactic bulge. Remnants bound to the black hole can possibly go through a second tidal disruption event.