The gamma ray burst - supernova connection
(PHYSorg.com Space & Earth)

A `core-collapse` supernova occurs when the iron core of a massive star collapses under the force of gravity and then rebounds, generating pressure waves and shocks that propagate outward. A superluminous supernovae is a rare class of core collapse supernovae whose luminosity, equal to 10-1000 billion suns, is too high to be powered by the usual process that drives supernovae, the radioactive decay of nickel (there is not enough nickel present to do it). The source of the energetics has been hotly contested, with suggestions including shocks from the ejected material or pulsating instabilities interacting with surrounding material. The most favored model, however, is the sustained injection of energy from a source like a spinning compact remnant: a neutron star or an accreting black hole.