Production of p Nuclei from r-Process Seeds: The νr Process

We present a new nucleosynthesis process that may take place on neutron -rich ejecta experiencing an intensive neutrino flux. The nucleosynthesis proceeds similarly to the standard r process, a sequence of neutron captures and beta decays with, however, charged -current neutrino absorption reactions on nuclei operating much faster than beta decays. Once neutron -capture reactions freeze out the produced r process, neutron -rich nuclei undergo a fast conversion of neutrons into protons and are pushed even beyond the beta stability line, producing the neutron -deficient p nuclei. This scenario, which we denote as the v r process, provides an alternative channel for the production of p nuclei and the short-lived nucleus 92 Nb. We discuss the necessary conditions posed on the astrophysical site for the v r process to be realized in nature. While these conditions are not fulfilled by current neutrino -hydrodynamic models of r -process sites, future models, including more complex physics and a larger variety of outflow conditions, may achieve the necessary conditions in some regions of the ejecta.