The Rates of Hypernovae and Gamma-Ray Bursts: Implications for their   Progenitors
  A critical comparison of estimates for the rates of hypernovae (HNe) and gamma-ray bursts (GRBs) is presented. Within the substantial uncertainties, the estimates are shown to be quite comparable and give a Galactic rate of $10^{-6}$ -- $10^{-5} $yr$^{-1}$ for both events. These rates are several orders of magnitude lower than the rate of core-collapse supernovae, suggesting that the evolution leading to a HN/GRB requires special circumstances, very likely due to binary interactions. Various possible binary channels are discussed, and it is shown that these are generally compatible with the inferred rates. 
Ph. Podsiadlowski, P. A. Mazzali, K. Nomoto, D. Lazzati, E. Cappellaro