Type II supernovae from prompt explosions

Evidence is cited that supernova 1987A involved a large explosion energy, {}(2--3)×{}10⁵¹ ergs. Such a large explosion energy has not come from delayed shocks to date, nor is it likely to. Improved physics in the presupernova evolution, especially the inclusion of Coulomb interactions, has brought the iron-core mass down by {}0.1M_ in the 13M_ star which has recently been evolved. We find that supernova explosion energies up to 3×{}10⁵¹ ergs can be obtained by the prompt-explosion mechanism, provided that a somewhat soft equation of state is used at supranuclear densities.