Particular Properties of Dense Supernova Matter

Abstract

Dense supernova matter composed of n, p, e-, e+, lie and ile is investigated in detail by solving self-consistently a set of finite-temperature Hartree-Fock equations with an effective nucleon interac­ tion. The effective interaction includes a phenomenological three-nucleon interaction to assure the saturation property of symmetric nuclear matter. Results of thermodynamic quantities and mixing ratios of respective components are analyzed and tabulated for wide region of density (p=(1-6)po) and temperature ( T=(10-40) MeV) by choosing the lepton fraction Y,=(0.3, 0.35, 0.4). We discuss particular properties of the matter such as the constancy of composition, the large proton fraction expressed by Yp(2/3) Yz+0.05 and the stiffened equation of state, and also discuss remarkable features of hot neutron stars at birth such as the fat density profile and the increasing temperature ·toward the center. It is shown that these features are caused essentially by the effects of neutrino trapping to generate the high and constant lepton fraction and isentropic nature, the effects which are absent in neutron star matter. A study on supernova matter is of increasing interest in relation to the mechanism of neutron star formation and the problems of newborn hot neutron stars. Supernova matter, which exists in a collapsing supernova core and eventually forms a hot neutron star at birth, is a new form of nucleon matter distinguished in the participa­ tion of degenerate neutrinos as well as electrons. It is characterized by almost constant entropy per baryon S ( =1.0-1.5) 1 > throughout the density p*> and also by a high and almost constant lepton fraction Yz ( =0.3-0.4),ll- 3 > in contrast with ordinary neutron star matter where S ~ 0 and Yz :S 0.05. These characteristics come from the effect that neutrinos begin to be trapped in a supernova core when p exceeds 10 11 12 g/ cc and thereby further collapse proceeds adiabatically keeping Yz almost constant. 4 >- 6 >