The $\hat{I}½$ process in the light of an improved understanding of supernova neutrino spectra

Abstract

We study the neutrino-induced production of nuclides in explosive supernova nucleosynthesis for progenitor stars with solar metallicity including neutrino nucleus reactions for all nuclei with charge numbers $Z<76$ with average neutrino energies in agreement with modern Supernova simulations. Considering progenitors with initial main sequence masses between 13~M${}_{\odot }$ and 30~M${}_{\odot }$, we find a significant production of ${}^{11}$B, ${}^{138}$La, and ${}^{180}$Ta by neutrino nucleosynthesis, despite the significantly reduced neutrino energies. The production of ${}^{19}$F turns out to be more sensitive to the progenitor mass and structure than to the $\hat{I}½$ process. With our complete set of cross sections we have identified effects of the $\hat{I}½$~process on several stable nuclei including ${}^{33}$S, ${}^{40}$Ar, ${}^{41}$K, ${}^{59}$Co, and ${}^{113}$In at the 10\% level. Neutrino-induced reactions contribute to a similar extent to the production of radioactive ${}^{26}$Al and increase the yield of ${}^{22}$Na by 50\%. Future ${\hat{I}}^3$~ray astronomy missions may reach the precision at which the contribution from the $\hat{I}½$~process becomes relevant. We find that the production of ${}^{22}$Na by the $\hat{I}½$~process could explain the Ne-E(L) component of meteoritic graphite grains. The $\hat{I}½$~process enhances the yield of ${}^{36}$Cl and we point out that the resulting ${}^{36}$Cl/${}^{35}$Cl ratio is in agreement with the values infrerred for the early solar system. Our extended set of neutrino-nucleus interactions also allows us to exclude any further effects of the $\hat{I}½$ process on stable nuclei and to quantify the effects on numerous, hitherto unconsidered radioactive nuclei, e.g., ${}^{36}$Cl, ${}^{72}$As, ${}^{84}$Rb, and ${}^{88}$Y.

18 pages, 14 figures, 3 tables; submitted to ApJ