Long, Cold, Early r Process? Neutrino-Induced Nucleosynthesis in He Shells Revisited

We revisit a ν-driven r-process mechanism in the He shell of a core-collapse supernova, finding that it could succeed in early stars of metallicity Z10^-3Z_, at relatively low temperatures and neutron densities, producing A~130 and 195 abundance peaks over ~10--20 s. The mechanism is sensitive to the ν emission model and to ν oscillations. We discuss the implications of an r process that could alter interpretations of abundance data from metal-poor stars, and point out the need for further calculations that include effects of the supernova shock.