New ²⁶P(p, )²⁷S Thermonuclear Reaction Rate and Its Astrophysical Implications in the rp-process

Accurate nuclear reaction rates for P-26(p, gamma)S-27 are pivotal for a comprehensive understanding of the rp-process nucleosynthesis path in the region of proton-rich sulfur and phosphorus isotopes. However, large uncertainties still exist in the current rate of P-26(p, gamma)S-27 because of the lack of nuclear mass and energy level structure information for S-27. We reevaluate this reaction rate using the experimentally constrained S-27 mass, together with the shell model predicted level structure. It is found that the P-26(p, gamma)S-27 reaction rate is dominated by a direct capture reaction mechanism despite the presence of three resonances at E = 1.104, 1.597, and 1.777 MeV above the proton threshold in S-27. The new rate is overall smaller than the other previous rates from the Hauser-Feshbach statistical model by at least 1 order of magnitude in the temperature range of X-ray burst interest. In addition, we consistently update the photodisintegration rate using the new S-27 mass. The influence of new rates of forward and reverse reaction in the abundances of isotopes produced in the rp-process is explored by postprocessing nucleosynthesis calculations. The final abundance ratio of S-27/P-26 obtained using the new rates is only 10% of that from the old rate. The abundance flow calculations show that the reaction path P-26(p, gamma)S-27(beta (+),nu)P-27 is not as important as previously thought for producing P-27. The adoption of the new reaction rates for P-26(p, gamma)S-27 only reduces the final production of aluminum by 7.1% and has no discernible impact on the yield of other elements.