Black hole emergence in supernovae

If a black hole formed in a core-collapse supernova is accreting material f rom the base of the envelope, the accretion luminosity could be observable in the supernova light curve. Here we continue the study of matter fallback onto a black hole in the wake of a supernova and examine realistic superno vae models that allow for an early emergence of the accretion luminosity. S uch cases may provide a direct observational identification of the black. h ole formed in the aftermath of the explosion. Our approach combines analyti c estimates and fully relativistic, radiation-hydrodynamic numerical comput ations. We employ a numerical hydrodynamical. scaling technique to accommod ate the diverse range of dynamical timescales in a single simulation. We fi nd that while in typical. Type II supernovae heating by radioactive decays dominates the late-time light curve, low-energy explosions of more massive stars should provide an important exception where the accretion luminosity will emerge while it is still relatively large. Our main focus is on the on ly current candidate for such an observation, the very unusual SN 1997D. Ow ing to the low energy of the explosion and the very small (2 x 10(-3) M-cir cle dot) inferred mass of Co-56 in the ejected envelope, we find that accre tion should become the dominant source of its luminosity during the year 20 00. The total luminosity at emergence is expected to he in the range 0.5-3 x 10(36) ergs s(-1), potentially detectable with the Hubble Space Telescope . We also discuss the more favorable case of explosions that eject negligib le amounts of radioactive isotopes and find that the black hole is likely t o emerge a few tens of days after the explosion, with a luminosity of simil ar to 10(37) ergs s(-1).