2004ApJ...601L.167M

Gamma-ray bursts can appear to be 100 times as luminous as supernovae, but their underlying energy source(s) have remained a mystery. However, there has been evidence for some time now of an association of gamma-ray bursts with supernovae of Type Ib and Ic, a fact that has been exploited by a number of models to explain the gamma-ray burst phenomenon. Here we interpret the results of basic observations of SN 1987A and of pulsars in globular clusters to propose the energy source, which powers at least some long-duration gamma-ray bursts, as core collapse following the merger of two white dwarfs, either as stars or as stellar cores. The beaming and intrinsic differences among gamma-ray bursts arise, at least in part, from differing amounts and composition of the gas in the merged stellar common envelopes, with the more energetic bursts resulting from mergers within less massive envelopes. In order for the beams/jets associated with gamma-ray bursts to form in mergers within massive common envelopes (as with SN 1987A), much of the intervening stellar material in the polar directions must be cleared out by the time of core collapse or the beams/jets themselves must clear their own path. The core collapse produces supernovae of Type Ib, Ic, or II (as with SN 1987A, a Type IIp supernova), leaving a weakly magnetized neutron star remnant with a spin period near 2 ms. There is no compelling reason to invoke any other model to account for gamma-ray bursts. Far from being an unusual event, SN 1987A is typical, having the same merger source of initiation as 95% of all supernovae, the rare exceptions being Type Ia supernovae induced via gradual accretion from a binary companion and Fe catastrophe Type II supernovae.