One-proton breakup of 24Si and the 23Al( p, γ )24Si reaction in type I x-ray bursts
Abstract
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 23Al(p, γ )24Si using indirect methods and, as a consequence, evaluate if sequential 2p capture on 22Mg seed nuclei is significant at high temperatures. Method: Nonresonant radiative proton capture on 23Al is investigated using the one-proton breakup of 24Si at 61 MeV/nucleon and the asymptotic normalization coefficient (ANC) for 24Sigs → 23Al + p is deduced. Results: From the ANC, the nonresonant component of the astrophysical S-factor for the 23Al(p, γ )24Si reaction is determined and, using other new experimental data the resonant component is re-evaluated. Conclusions: The 23Al(p, γ )24Si reaction is of interest for type I XRB nucleosynthesis and its reaction rate can affect both the 22Na abundance and the total energy output. New determinations of the rates for the 22Mg(p, γ )23Al(p, γ )24Si reaction chain are provided here and we point to the need that they be included in XRB scenarios.