TIDAL DISRUPTIONS BY SUPERMASSIVE BLACK-HOLES - HYDRODYNAMIC EVOLUTION OF STARS ON A SCHWARZSCHILD BACKGROUND

We present a three-dimensional numerical study of tidal disruption of a main-sequence star (M* = 1 M.) by a supermassive black hole (M(h) = 10(6) M.). The simulations include general relativistic effects which are important in this regime. We analyze stars in a marginally bound orbit around the black hole with pericentric separation of a few Schwarzschild radii. We show that during a close passage, as a result of relativistic effects analogous to the perihelion shift, the trajectories of the debris of the star fan out into a crescent-like shape centered on the black hole. We also discuss the increase of the central density of the star as it approaches pericentric distance, the fraction of the debris accreted by the hole, its accretion rate, the distribution of debris orbits bound to the hole, and the velocity of unbound ejected material. We compare these results with the disruption of the star by a Newtonian point mass.