ULTRA-CLOSE ENCOUNTERS OF STARS WITH MASSIVE BLACK HOLES: TIDAL DISRUPTION EVENTS WITH PROMPT HYPERACCRETION

A bright flare from a galactic nucleus followed at late times by a t(-5/3) decay in luminosity is often considered the signature of the complete tidal disruption of a star by a massive black hole. The flare and power-law decay are produced when the stream of bound debris returns to the black hole, self-intersects, and eventually forms an accretion disk or torus. In the canonical scenario of a solar-type star disrupted by a 10(6) M-circle dot black hole, the time between the disruption of the star and the formation of the accretion torus could be years. We present fully general relativistic simulations of a new class of tidal disruption events involving ultra-close encounters of solar-type stars with intermediate mass black holes. In these encounters, a thick disk forms promptly after disruption, on timescales of hours. After a brief initial flare, the accretion rate remains steady and highly super-Eddington for a few days at similar to 10(2) M-circle dot yr(-1).