Explosive Hydrogen Burning of ²⁷Si, ³¹S, ³⁵Ar, and ³⁹Ca in Novae and X-Ray Bursts

Stellar reaction rates for proton captures on the nuclei ²⁷Si, ³¹S, ³⁵Ar, and ³⁹Ca are estimated from the most recent nuclear structure information available. Reliable mirror-state correspondences are found by using the isobaric multiplet mass equation. An improved method for calculating proton partial widths is applied. Systematic comparisons of excitation energies, spectroscopic factors, proton partial widths, and γ-ray partial widths for states of the same isospin multiplet are presented. Stellar reaction-rate uncertainties are deduced, and our reaction rates are compared to previous estimates. Reaction network calculations are performed to investigate implications of the new reaction rates for nucleosynthesis in novae and X-ray bursts. Our recommended reaction rates are varied within their assigned uncertainties, and we find only minor effects on the nuclear energy generation and the final abundances after the outbursts. Thus, contrary to previous claims, we find no compelling reason for measuring the proton capture reactions on ²⁷Si, ³¹S, ³⁵Ar, and ³⁹Ca by using radioactive ion beams.