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Session 78 - Stars - Young and Old, Large and Small.
Display session, Wednesday, January 15
Metropolitan Ballroom,

[78.02] Weak Interaction Rates in Convective Silicon Burning in Massive Stars

G. Bazan, D. Arnett (Steward Obs.)

Understanding the full effects of convective silicon burning are crucial towards the defining the initial state of core collapse. Since the convection which occurs is wholly dependent on the competition between nuclear energy and neutrino losses, we must determine the role of the individual processes which contribute toward the energy balance. The nuclear processes leading to nuclear statistical equilibrium are fairly well known, as are the neutrino energy losses from pair, photo, plasma, bremsstrahlung, and recombination processes. However, the role of neutrino losses from weak interactions among intermediate nuclei are not so well defined. The first problem is the rates themselves. Previous rate evaluations had a poor description of the Gamow-Teller resonance energy and width. We will present some new rates which account for individual low energy transitions as well as new theoretical descriptions of the Gamow-Teller resonance. New calculations of convective silicon burning are presented to study the dependencies on weak interaction rates. Both 1D hydrostatic models and 2D hydrodynamic models are married to a large nuclear network ( 160 nuclei) and employ the newly calculated weak interaction rates. The collective role of iron-peak nuclei as a sink of energy via neutrino losses from the weak interactions is emphasized along with any hydrodynamical effects that play upon the local flavor of the neutrino emission, which regulates the convection. Comparisons are drawn with models using schematic representations of energy generation and neutrino losses. The resulting behavior of core collapse

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