Three-Dimensional Simulations of Tidally Disrupted Solar-Type Stars and the Observational Signatures of Shock Breakout

Abstract

We describe a three-dimensional simulation of a $1 M_{\odot}$ solar-type star approaching a $10^{6} M_{\odot}$ black hole on a parabolic orbit with a pericenter distance well within the tidal radius. While falling towards the black hole, the star is not only stretched along the orbital direction but even more severely compressed at right angles to the orbit. The overbearing degree of compression achieved shortly after pericenter leads to the production of strong shocks which largely homogenize the temperature profile of the star, resulting in surface temperatures comparable to the initial temperature of the star's core. This phenomenon, which precedes the fallback accretion phase, gives rise to a unique double-peaked X-ray signature that, if detected, may be one of the few observable diagnostics of how stars behave under the influence of strong gravitational fields. If $\sim 10^{6} M_{\odot}$ black holes were prevalent in small or even dwarf galaxies, the nearest of such flares may be detectable by EXIST from no further away than the Virgo Cluster.