Rates of Observable Black Hole Emergence in Supernovae

Abstract

A newly formed black hole may be directly identified if late-time accretion of material from the base of the ejected envelope generates a luminosity that is observable in the tail of the supernova light curve. In this work we estimate the rate at which events where the black hole ``emerges'' in the supernova light curve can be detected with present capabilities. Our investigation is based on an analytical model of the accretion luminosity at emergence as a function of progenitor mass, coupled to the inferred rate of observed Type II supernovae in nearby galaxies. We find through a parameter survey that under optimistic assumptions the potential rate of observable events can be as high as several per year. However, supernovae which produce black holes are also likely to be low energy explosions and therefore subluminous, as was the case for the best candidate to date, SN1997D. If black hole-forming supernovae are underdetected owing to lower luminosities, the rate of observing black hole emergence is probably not larger than once every few years. We therefore emphasize the importance of dedicated searches for nearby supernovae as well as faint supernovae projects for improving the prospects of observationally certifying the supernova--black hole connection.