On the Frequency and Remnants of Hypernovae

Under the hypothesis that some fraction of massive stellar core collapses give rise to unusually energetic events termed hypernovae, I examine the required rates assuming that some fraction of such events yield gamma-ray bursts. I then discuss evidence from studies of pulsars and r-process nucleosynthesis that independently suggests the existence of a class of unusually energetic events. Finally, I describe a scenario that links these different lines of evidence as support for the hypernova hypothesis.