S. Kahana

Collapse of 9 solar mass stars

General relativistic hydrodynamical calculations of the collapse of O + Ne + Mg cores of a 9 solar mass star are reported. Collapse is induced by rapid electron captures as the O + Ne + Mg is burned to nuclear statistical equilibrium. The high entropy in the core after burning leads to a large abundance of free protons which readily capture electrons. This leads to large neutrino losses and a correspondingly small infalling homologous core. The hydrodynamic shock thus forms at a small mass point. The shock stalls before reaching the edge of the O + Ne + Mg core and thereby fails to produce a successful supernova explosion by the direct mechanism. No enhancement in the shock energy due to nuclear burning is found. 16 references.

Collapsing white dwarfs

The results of the hydrodynamic collapse of an accreting C + O white dwarf are presented. Collapse is induced by electron captures in the iron core behind a conductive deflagration front. The shock wave produced by the hydrodynamic bounce of the iron core stalls at about 115 km, and thus a neutron star formed in such a model would be formed as an optically quiet event. 19 references.

P ANNIHILATION IN AU + AU AT 11 GEV/C. AUTHORS' REPLY

Antinucleon production in heavy ion collisions is potentially an excellent signal for unusual phenomena in hot and dense matter. However, at the low energies available at the AGS the annihilation process must be handled with care. In this Comment, we consider the case of Au + Au collisions at approximately 11 GeV/c, applying the ARC treatment of pbar production and annihilation to the analysis of experiment E878. It is apparent that classical screening introduced for Si + Au is crucial in the understanding of data obtained with the more massive projectile. Unfortunately, there seems no necessity for invoking unusual behaviour in the Au + Au system.

{ovr {ital p}} Annihilation in Au+Au at 11GeV/{ital c}

Antinucleon production in heavy ion collisions is potentially an excellent signal for unusual phenomena in hot and dense matter. However, at the low energies available at the AGS the annihilation process must be handled with care. In this Comment, we consider the case of Au + Au collisions at approximately 11 GeV/c, applying the ARC treatment of pbar production and annihilation to the analysis of experiment E878. It is apparent that classical screening introduced for Si + Au is crucial in the understanding of data obtained with the more massive projectile. Unfortunately, there seems no necessity for invoking unusual behaviour in the Au + Au system.

Pbar Annihilation in Au+Au at AGS Energies

Antinucleon production in heavy ion collisions is potentially an excellent signal for unusual phenomena in hot and dense matter. However, at the low energies available at the AGS the annihilation process must be handled with care. In this Comment, we consider the case of Au + Au collisions at approximately 11 GeV/c, applying the ARC treatment of pbar production and annihilation to the analysis of experiment E878. It is apparent that classical screening introduced for Si + Au is crucial in the understanding of data obtained with the more massive projectile. Unfortunately, there seems no necessity for invoking unusual behaviour in the Au + Au system.

Successful Supernovae, the Anatomy of Shocks: Neutrino Emission and the Adiabatic Index

Hydrodynamic calculations of stellar collapse in Type II Supernova are described using a variable nuclear adiabatic index and compressibility for the nuclear equation of state at high density. Initial models employing a relatively small mass core with low central entropy are necessary to achieve viable shocks; near success the models are sensitive to both neutrino emission and the high density equation of state. The treatment of neutrino production and transport is sketched and recent results reported.