We report on the nonnegligible energy released by the 13C(α, n)16O reaction and the related neutron capture reactions in interior convective shells developed during the thermal pulsation phase of asymptotic giant branch (AGB) stars of low mass and low metallicity. Over 104 L⊙ are generated within a thermal pulse convective shell from the combination of the 13C(α, n)16O, neutron capture, and beta decay reactions. The inclusion of this energy source in the theoretical evolution of an AGB thermal pulse is shown to alter the evolution of the convective shell boundaries and, hence, how the 13C is ingested into the convective shell. By iterating between a nucleosynthesis code and a stellar model, we find a "converged" model in which the neutron density arising from the 13C source is substantially higher and the overall mean exposure of the irradiated material is lower than cases where no energy is taken into account. With these modifications in s-process parameters, the calculated abundance ratios for r-only to s-only nuclei at the same mass number remains surprisingly constant, but still does not eliminate the overproduction of 96Zr, which disagrees with observation.
- Nuclear reactions, nucleosynthesis, abundances
- Stars: Interiors