Proton vs. neutron captures in the neutrino winds of core-collapse supernovae

Abstract

Recent one-dimensional (1D) hydrodynamical simulations of core-collapse supernovae (CCSNe) with a sophisticated treatment of neutrino transport indicate the neutrino-driven winds being proton-rich all the way until the end of their activity. This seems to exclude all possibilities of neutron-capture nucleosynthesis, but provide ideal conditions for the νp-process, in neutrino winds. New 2D explosion simulations of electron-capture supernovae (ECSNe; a subset of CCSNe) exhibit, however, convective neutron-rich lumps, which are absent in the 1D case. Our nucleosynthesis calculations indicate that these neutron-rich lumps allow for interesting production of elements between iron group and N = 50 nuclei (Zn, Ge, As, Se, Br, Kr, Rb, Sr, Y, Zr, with little Ga). Our models do not confirm ECSNe as sources of the strong r-process (but possibly of a weak r-process up to Pd, Ag, and Cd in the neutron-rich lumps) nor of the νp-process in the subsequent proton-rich outflows. We further study the νp-process with semi-analytic models of neutrino winds assuming the physical conditions for CCSNe. We also explore the sensitivities of some key nuclear reaction rates to the nucleosynthetic abundances. Our result indicates that the ν/p-process in CCSNe (other than ECSNe) can be the origin of p-nuclei up to A = 108, and even up to A = 152 in limiting conditions.