Effect of initial thermal structure on the collapse and explosion of iron stellar cores

Abstract

We investigate the adiabatic collapse of 1.7 and 1.5 M/sub sun/ iron cores using the LLPR equation of state and Fermi gas electron capture rates, and assuming complete neutrino trapping. For a variety of initial configurtions, infall deleptonization leaves a homologous core of only 1 M/sub circle-solid/; the large overlay mass that the shock must penetrate and dissociate then prevents significant ejection of mass and kinetic energy. If all electron capture is artificially suppressed, we do obtain ejection of 0.1 M/sub circle-solid/, with 5 x 10/sup 50/ and 2 x 10/sup 52/ ergs kinetic energy for the 1.7 and 1.5 M/sub circle-solid/ initial cores, respectively. In stars of these masses, neutrino processes are not responsible for supernova explosion but instead kill the otherwise efficient thermal stiffening mechanism. The initial iron core configuration needed for a supernovva explosion must be cooler, and therefore lighter and more isentropic, than those cores heretofore considdered. Such a cooler pre-supernova configuration can evolve if hydrostatic electron capture leads to greater neutrino cooling before the contraction becomes dynamic.