Lixin Dai, Andres Escala, Paolo Coppi
We have carried out general relativistic particle simulations of stars tidally disrupted by massive black holes. When a star is disrupted in a bound orbit with moderate eccentricity instead of a parabolic orbit, the temporal behavior of stellar debris changes qualitatively. Stellar debris travels in bound orbits, and returns to the pericenter within a short spread of time, so the fallback rate is much higher than the Eddington rate. Further if the star is disrupted very close to the hole in a regime where general relativity is important, the stellar and the debris orbits display general relativistic precession. Apsidal motion can make the debris stream cross itself after several orbits, which leads to fast dissipation of the debris binding energy. If the star is disrupted in an inclined orbit around a spinning hole, Lense-Thirring precession reduces the probability of such self-crossing, and circularization cannot happen in dynamical timescale. Although we have not computed the light curve using hydrodynamical simulations, examination of dynamics suggests that quasi-periodic flares with small durations, produced by repeated debris pericenter passages, should be exhibited in the early-time light curve. The late-time light curve might still show power-law behavior which is generic to accretions. We suggest that in order to detect these non-standard tidal disruption events in future surveys, the detection triggers should be extended to capture such short-term variations which do not look like standard tidal disruption flares. Also, the initial period of the light curve should be paid more attention as it tells more physics.
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http://arxiv.org/abs/1303.4837
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