The impact of asymmetric neutrino emissions on nucleosynthesis in core-collapse supernovae

Abstract

We investigate the impact of asymmetric neutrino emissions on the explosive nucleosynthesis in neutrino-driven core-collapse supernovae (CCSNe). We find that the asymmetric emissions tend to yield larger amounts of proton-rich ejecta (electron fraction, $Y_e > 0.51$) in the hemisphere of the higher $\\nu_{\\rm e}$ emissions, meanwhile neutron-rich matter ($Y_e < 0.49$) are ejected in the opposite hemisphere of the higher ${\\bar \\nu}_{\\rm e}$ emissions. For larger asymmetric cases with $\\ge 30\\%$, the neutron-rich ejecta is abundantly produced, in which there are too much elements heavier than Zn compared to the solar abundances. This may place an upper limit of the asymmetric neutrino emissions in CCSNe. The characteristic features are also observed in elemental distribution; (1) abundances lighter than Ca are insensitive to the asymmetric neutrino emissions: (2) the production of Zn and Ge is larger in the neutron-rich ejecta even for smaller asymmetric cases with $\\le 10\\%$. We discuss these observational consequences, which may account for the (anti-)correlations among asymmetries of heavy elements and neutron star kicks in supernova remnants (SNRs). Future SNR observations of the direct measurement for the mass and spatial distributions of $\\alpha$ elements, Fe, Zn and Ge will provide us the information on the asymmetric degree of neutrino emissions.