Light curves from polytropic stars tidally disrupted by a supermassive black hole

Abstract

The observation of X-ray flares due to a stellar disruption is one of the ways we can indirectly observe a black hole. These events are characterized by a light curve that falls off as the power law t^-5/3 at large t. However, as argued by Lodato et al, the early part of the light curve bears an imprint of the interior of the disrupted star. In this paper, we extend the work of Lodato et al by calculating the structure of polytropic stars and their expected tidal disruption light curves. As expected, all of their light curves display the t^-5/3 proportionality at late times, but differ at early times. Stars with stiffer equations of state are characterized by higher peak luminosities and earlier onsets of the peak luminosity.