One-proton breakup of24Si and the23Al(p,γ)24Si reaction in type I x-ray bursts

Abstract

Background: To understand explosive hydrogen burning in stars and to explore various explosive scenarios such as type I x-ray bursts (XRBs), reliable reaction rates are needed. The cross sections for radiative proton capture on near-dripline nuclei are necessary for the determination of the reaction rates, but cannot be measured directly.Purpose: To determine the reaction rate for the radiative proton capture reaction ${}^{23}\mathrm{Al}{(p,\ensuremath{\gamma})}^{24}\mathrm{Si}$ using indirect methods and, as a consequence, evaluate if sequential $2p$ capture on ${}^{22}$Mg seed nuclei is significant at high temperatures.Method: Nonresonant radiative proton capture on ${}^{23}$Al is investigated using the one-proton breakup of ${}^{24}$Si at 61 MeV/nucleon and the asymptotic normalization coefficient (ANC) for ${}^{24}{\mathrm{Si}}_{\mathrm{gs}}\ensuremath{\rightarrow}{}^{23}\mathrm{Al}+p$ is deduced.Results: From the ANC, the nonresonant component of the astrophysical $S$-factor for the ${}^{23}\mathrm{Al}{(p,\ensuremath{\gamma})}^{24}\mathrm{Si}$ reaction is determined and, using other new experimental data the resonant component is re-evaluated.Conclusions: The ${}^{23}\mathrm{Al}{(p,\ensuremath{\gamma})}^{24}\mathrm{Si}$ reaction is of interest for type I XRB nucleosynthesis and its reaction rate can affect both the ${}^{22}$Na abundance and the total energy output. New determinations of the rates for the ${}^{22}\mathrm{Mg}{(p,\ensuremath{\gamma})}^{23}\mathrm{Al}{(p,\ensuremath{\gamma})}^{24}\mathrm{Si}$ reaction chain are provided here and we point to the need that they be included in XRB scenarios.