Explosive hydrogen burning of Si-27, S-31, Ar-35, and Ca-39 in novae and X-ray bursts

Stellar reaction rates for proton captures on the nuclei Si-27, S-31, Ar-35 , and Ca-39 are estimated from the most recent nuclear structure informatio n available. Reliable mirror-state correspondences are found by using the i sobaric multiplet mass equation. An improved method for calculating proton partial widths is applied. Systematic comparisons of excitation energies, s pectroscopic factors, proton partial widths, and gamma-ray partial widths f or stales of the same isospin multiplet are presented. Stellar reaction-rat e uncertainties are deduced, and our reaction rates are compared to previou s estimates. Reaction network calculations are performed to investigate imp lications of the new reaction rates for nucleosynthesis in novae and X-ray bursts. Our recommended reaction rates are varied within their assigned unc ertainties, and we find only minor effects on the nuclear energy generation and the final abundances after the outbursts. Thus, contrary to previous c laims, ive find no compelling reason for measuring the proton capture react ions on Si-27, S-31, Ar-35, and Ca-39 by using radioactive ion beams.