Supernova fallback and the emergence of a black hole

We present the first fully relativistic investigation of matter fallback in a supernova. We investigate spherically symmetric supernova fallback using a relativistic radiation hydrodynamics Lagrangian code that handles radiat ion transport in all regimes. Our goal is to answer the fundamental questio ns: did SN 1987A produce a black hole and, if so, when will the hole become detectable? We compute the Light curve, assuming that a black hole has bee n formed during the explosion, and compare it with the observations. Our pr eliminary calculations lack radioactive energy input and adopt a very simpl e chemical composition (pure hydrogen). As a result, our computed models ca nnot fit the observed data of SN 1987A in detail. Nevertheless, we can show that, during the first hours, the accretion how is self-regulated and the accretion luminosity stays very close to the Eddington limit. The light cur ve is completely dominated, during the first few weeks, by the emission of the stellar envelope thermal energy and resembles that obtained in '"standa rd" supernova theory. Only long after hydrogen recombination takes place is there even a chance to actually detect radiation from the accreting black hole above the emission of the expanding envelope. The presence of a black hole is thus not inconsistent with observations to date. Because of the exp onential decay of the Ti-44 radioactive heating rate, the date of the emerg ence of the black hole is not very sensitive to the actual parameters of th e models and turns out to be about 1000 yr. The bulk of the emission then i s expected to be in the visible band but will be unobservable with present instrumentation. We discuss the implications of our results in connection w ith the possible emergence of black holes in other supernovae.