In Core-collapse Supernovae: Sensitivity to the Rates of the Triple Alpha and C(α, Γ)o Reactions

We have studied the sensitivity to variations in the the triple alpha and C(α, γ)O reaction rates of the production of Al, Ti, and Fe in core-collapse supernovae. We used the KEPLER code to model the evolution of 15M⊙, 20M⊙, and 25M⊙ stars to the onset of core collapse and simulated the ensuing supernova explosion using a piston model for the explosion. Calculations were performed for the Anders and Grevesse (1989) and Lodders (2003) abundances. Over a range of ±2σ for each helium-burning rate the production of Al, Fe, and their ratio vary by factors of five or more. For some species, similar variations were observed for much smaller rate changes, 0.5σ or less. The production of Ti was less sensitive to changes in the helium-burning rates. Production of all three isotopes depended on the solar abundance set used for the initial stellar composition. Subject headings: gamma-rays: general, nuclear reactions, nucleosynthesis, abundances, supernovae: