Authors: Michael Kesden
Date: 26 Jul 2012
Abstract: A star orbiting a supermassive black hole can be tidally disrupted if the black hole's gravitational tidal field exceeds the star's self gravity at pericenter. Some of stellar tidal debris can become gravitationally bound to the black hole and be subsequently accreted, leading to a bright electromagnetic flare. In the Newtonian limit, this flare will have a light curve that scales as tˆ-5/3 if the tidal debris has a flat distribution in binding energy. We investigate the time dependence of the black-hole mass accretion rate when tidal disruption occurs close enough the black hole that relativistic effects are significant. We find that for orbits with pericenters comparable to the radius of the marginally bound circular orbit, relativistic effects can double the peak accretion rate and halve the time it takes to reach this peak accretion rate. The accretion rate depends on both the magnitude of the black-hole spin and its orientation with respect to the stellar orbit; for orbits with a given pericenter radius in Boyer-Lindquist coordinates, a maximal black-hole spin anti-aligned with the orbital angular momentum leads to the largest peak accretion rate.
© M. Vallisneri 2012 — last modified on 2010/01/29
Tantum in modicis, quantum in maximis