Nucleosynthesis in the Hot Convective Bubble in Core‐Collapse Supernovae

As an explosion develops in the collapsed core of a massive star, neutrinoemission drives convection in a hot bubble of radiation, nucleons, and pairsjust outside a proto-neutron star. Shortly thereafter, neutrinos drive awind-like outflow from the neutron star. In both the convective bubble and theearly wind, weak interactions temporarily cause a proton excess (Ye > 0.5) todevelop in the ejected matter. This situation lasts for at least the firstsecond, and the approximately 0.05 - 0.1 solar masses that is ejected has anunusual composition that may be important for nucleosynthesis. Using tracerparticles to follow the conditions in a two-dimensional model of a successfulsupernova explosion calculated by Janka, Buras & Rampp (2003), we determine thecomposition of this material. Most of it is helium and 56Ni. The rest isrelatively rare species produced by the decay of proton-rich isotopes unstableto positron emission. In the absence of pronounced charged-current neutrinocapture, nuclear flow will be held up by long-lived waiting point nuclei in thevicinity of 64Ge. The resulting abundance pattern can be modestly rich in a fewinteresting rare isotopes like 45Sc, 49Ti, and 64Zn. The present calculationsimply yields that, when compared with the production of major species in therest of the supernova, are about those needed to account for the solarabundance of 45Sc and 49Ti. Since the synthesis will be nearly the same instars of high and low metallicity, the primary production of these species mayhave discernible signatures in the abundances of low metallicity stars. We alsodiscuss uncertainties in the nuclear physics and early supernova evolution towhich abundances of interesting nuclei are sensitive.