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Session 97 - Supernovae.
Oral session, Wednesday, January 17
Salon del Rey Central, Hilton

[97.06] Silicon Burning I: The Importance of Neutronization to the Physics of Quasi-Equilibrium

W. R. Hix (UT Austin), F. -K. Thielemann (Univ. of Basel)

As the most tightly bound nuclei, the `Iron Peak' nuclei are the culmination of nuclear energy generation in astrophysical environments and the result of Nuclear Statistical Equilibrium (NSE). Our re-examination of silicon burning, the mechanism by which the nuclei of the iron peak are produced, has revealed a number of potential improvements to our understanding of this ultimate stage of astrophysical nuclear energy generation. We will discuss results gleaned from simulation work done with a large nuclear network (300 nuclei and 3000 reactions) and from independent calculations of equilibrium abundance distributions, which offer new insights into the quasi-equilibrium mechanism and the approach to NSE. We find that the degree to which the matter has been neutronized is of great importance, not only to the final products, but also to the rate of energy generation and the membership of the quasi-equilibrium groups. Furthermore, we find that, as a result of quasi-equilibrium, incomplete silicon burning results in neutron richness among the isotopes of the iron group much larger than the global neutronization would indicate. In light of our findings, we will also discuss the applicability of approximations for silicon burning commonly employed in hydrodynamic simulations.

Program listing for Wednesday