Improved thermonuclear rate of 42Ti(p,?)43V and its astrophysical implication in the rp process

Context. Accurate Ti-42(p,gamma)V-43 reaction rates are crucial for understanding the nucleosynthesis path of the rapid capture process (rp process) that occurs in X-ray bursts. Aims. We aim to improve the thermonuclear rates of Ti-42(p,gamma)V-43 based on more complete resonance information and a more accurate direct component, together with the recently released nuclear masses data. We also explore the impact of the newly obtained rates on the rp process. Methods. We reevaluated the reaction rate of Ti-42(p,gamma)V-43 by the sum of the isolated resonance contribution instead of the Hauser-Feshbach statistical model. We used a Monte Carlo method to derive the associated uncertainties of new rates. The nucleosynthesis simulations were performed via the NuGrid post-processing code ppn. Results. The new rates di ffer from previous estimations due to the use of a series of updated resonance parameters and a direct S factor. Compared with the previous results from the Hauser-Feshbach statistical model, which assumes compound nucleus V-43 with a su fficiently high-level density in the energy region of astrophysical interest, large di fferences exist over the entire temperature region of rp-process interest, up to two orders of magnitude. We consistently calculated the photodisintegration rate using our new nuclear masses via the detailed balance principle, and found the discrepancies among the different reverse rates are much larger than those for the forward rate, up to ten orders of magnitude at the temperature of 10(8) K. Using a trajectory with a peak temperature of 1.95x10(9) K, we performed the rp-process nucleosynthesis simulations to investigate the impact of the new rates. Our calculations show that the adoption of the new forward and reverse rates result in abundance variations for Sc and Ca of 128% and 49%, respectively, compared to the variations for the statistical model rates. On the other hand, the overall abundance pattern is not significantly a ffected. The results of using new rates also confirm that the rp-process path does not bypass the isotope V-43. Conclusions. Our study found that the Hauser-Feshbach statistical model is inappropriate to the reaction rate evaluation for Ti-42(p,gamma)V-43. The adoption of the new rates confirms that the reaction path of Ti-42(p,gamma)V-43(p,gamma)Cr-44(beta(+))V-44 is a key branch of the rp process in X-ray bursts.

Automated summary

The accurate evaluation of Ti-42(p,gamma)V-43 reaction rates is crucial for understanding the rp process in X-ray bursts. This study aimed to improve the rates using updated resonance parameters, direct S factor, and nuclear masses data. The results showed significant differences in the rates compared to previous estimations and confirmed the importance of the Ti-42(p,gamma)V-43 reaction path in the rp process.