NewP30(p,γ)S31resonances and oxygen-neon nova nucleosynthesis

Abstract

Enriched isotopic abundance ratios of $^{30}\mathrm{Si}$/$^{28}\mathrm{Si}$ in several presolar SiC and graphite grains qualitatively indicate massive oxygen-neon (ONe) nova origins but fall short of hydrodynamic ONe nova model ejecta predictions by as much as an order of magnitude. The astrophysical $^{30}\mathrm{P}$($p,\ensuremath{\gamma}$)$^{31}\mathrm{S}$ reaction rate uncertainty at ONe nova temperatures ($0.10lTl0.35$ GK) spans several orders of magnitude through which the predicted amount of ejected $^{30}\mathrm{Si}$ can vary by a factor of 100. By measuring triton momenta from the $^{31}\mathrm{P}$($^{3}\mathrm{He}$,$t$)$^{31}\mathrm{S}$ reaction at 20 MeV, the energies of $^{30}\mathrm{P}$ $+p$ resonances in the Gamow window for ONe novae have been determined to better than \ifmmode\pm\else\textpm\fi{}3 keV, and two new resonances at ${E}_{\mathrm{c}.\mathrm{m}.}=194.0(25)$ and 266.4(27) keV that likely dominate the $^{30}\mathrm{P}$($p,\ensuremath{\gamma}$)$^{31}\mathrm{S}$ rate for $0.08lTl0.25$ GK have been resolved. A resulting increase in the experimentally determined $^{30}\mathrm{P}$($p,\ensuremath{\gamma}$)$^{31}\mathrm{S}$ reaction rate puts it in accord with Hauser-Feshbach statistical model estimates for $0.08lTl0.40$ GK, supporting conclusions drawn from ONe nova model studies that employed a Hauser-Feshbach rate.