Tidal disruptions of main sequence stars -- II. Simulation methodology and stellar mass dependence of the character of full tidal disruptions

Taeho Ryu, Julian Krolik, Tsvi Piran, Scott C. Noble

Published 2020-01-08Version 1

This is the second in a series of papers presenting the results of fully general relativistic simulations of stellar tidal disruptions in which the stars' initial states are realistic main-sequence models. In the first paper (Paper I), we gave an overview of this program and discussed the principal observational implications of our work. Here we describe our calculational method and provide details about the outcomes of full disruptions, focusing on the stellar mass dependence of the outcomes for a black hole of mass $10^{6}\rm{M}_{\odot}$. We consider eight different stellar masses, from $0.15~{\rm M}_\odot$ to $10~{\rm M}_\odot$. We find that, relative to the traditional order-of-magnitude estimate $r_{\rm t}$, the physical tidal radius of low-mass stars ($M_{\star} \lesssim 0.7~ {\rm M}_\odot$) is larger by tens of percent, while for high-mass stars ($M_{\star} \gtrsim1~ {\rm M}_\odot$) it is smaller by a factor 2--2.5. The traditional estimate of the range of energies found in the debris is $\approx 1.4\times$ too large for low-mass stars, but is a factor $\sim 2$ too small for high-mass stars; in addition, the energy distribution for high-mass stars has significant wings. For all stars undergoing tidal encounters, we find that mass-loss continues for many stellar vibration times because the black hole's tidal gravity competes with the instantaneous stellar gravity at the star's surface until the star has reached a distance from the black hole $\sim O(10)r_{\rm t}$.