Constraining the ³⁰P(p,γ)³¹S reaction rate in ONe nova nucleosynthesis via ³¹Cl β-delayed proton decay using GADGET

Classical novae occur in stellar binaries involving a white dwarf and a hydrogen-rich companion star. Accreted material from the donor star is compressed, heated, and mixed with the outer layers of the underlying white dwarf until it ignites in a thermonuclear runaway. For the most massive oxygen-neon (ONe) white dwarfs, the ³⁰P(p,γ)³¹S reaction rate has been identified as the largest remaining nuclear uncertainty for modeling A>29 nucleosynthesis. The β⁺ decay of ³¹Cl strongly populates a 260-keV resonance which dominates the total rate for proton capture on ³⁰P. The Gaseous Detector with Germanium Tagging (GADGET) was built to measure the proton branching ratio of this resonance via ³¹Cl(βp)³⁰P. Here we present the results of an experiment at the National Superconducting Cyclotron Laboratory, in which we measured the weakest β-delayed proton intensity ever for resonances below 400 keV. With this result, shell model calculations for the lifetime, and past work on other resonances, we computed the thermonuclear rate for ³⁰P(p,γ)³¹S. Simulations were performed using this newly constrained rate to predict the chemical and isotopic abundances of ONe nova ejecta. We compare these expected ratios with presolar grain data and astronomical observations to calibrate nuclear thermometers.