New ³⁰P(p,γ)³¹S resonances and oxygen-neon nova nucleosynthesis

Enriched isotopic abundance ratios of ³⁰Si/²⁸Si 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 ³⁰P(p,γ)³¹S 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 ³⁰Si can vary by a factor of 100. By measuring triton momenta from the ³¹P(³He,t)³¹S reaction at 20 MeV, the energies of ³⁰P +p resonances in the Gamow window for ONe novae have been determined to better than ±3 keV, and two new resonances at E_c.m.=194.0(25) and 266.4(27) keV that likely dominate the ³⁰P(p,γ)³¹S rate for 0.08<T<0.25 GK have been resolved. A resulting increase in the experimentally determined ³⁰P(p,γ)³¹S 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.