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 ${}^{30}\mathrm{P}$($p,\gamma$)${}^{31}\mathrm{S}$ reaction rate uncertainty at ONe nova temperatures ($0.10<T<0.35$ 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 ±3 keV, and two new resonances at $E_{\mathrm{c}.\mathrm{m}.}=194.0(25)$ and 266.4(27) keV that likely dominate the ${}^{30}\mathrm{P}$($p,\gamma$)${}^{31}\mathrm{S}$ rate for $0.08<T<0.25$ GK have been resolved. A resulting increase in the experimentally determined ${}^{30}\mathrm{P}$($p,\gamma$)${}^{31}\mathrm{S}$ reaction rate puts it in accord with Hauser-Feshbach statistical model estimates for $0.08<T<0.40$ GK, supporting conclusions drawn from ONe nova model studies that employed a Hauser-Feshbach rate.

• Received 12 August 2007

DOI:https://doi.org/10.1103/PhysRevC.76.052802