The p-process in exploding rotating massive stars

Choplin, A.; Goriely, S.; Hirschi, R; Tominaga, N.; Meynet, G.

Abstract

Context. The p-process nucleosynthesis can explain proton-rich isotopes that are heavier than iron, which are observed in the Solar System, but discrepancies still persist (e.g. for the Mo and Ru p-isotopes), and some important questions concerning the astrophysical site(s) of the p-process remain unanswered.

Aims. We investigate how the p-process operates in exploding rotating massive stars that have experienced an enhanced s-process nucleosynthesis during their life through rotational mixing.

Methods. With the Geneva stellar evolution code, we computed 25 M-circle dot stellar models at a metallicity of Z = 10(-3) with different initial rotation velocities and rates for the still largely uncertain O-17(alpha,gamma)Ne-21 reaction. The nucleosynthesis calculation, followed with a network of 737 isotopes, was coupled to stellar evolution, and the p-process nucleosynthesis was calculated in post-processing during both the final evolutionary stages and spherical explosions of various energies. The explosions were modelled with a relativistic hydrodynamical code.

Results. In our models, the p-nuclides are mainly synthesized during the explosion, but not much during the ultimate hydrostatic burning stages. The p-process yields mostly depend on the initial number of trans-iron seeds, which in turn depend on the initial rotation rate. We found that the impact of rotation on the p-process is comparable to the impact of rotation on the s-process. From no to fast rotation, the s-process yields of nuclides with mass number A < 140 increase by 3-4 dex, and so do the p-process yields. Fast rotation with a lower O-17(alpha, gamma) rate significantly produces s- and p-nuclides with A >= 140. The dependence of the p-process yields on the explosion energy is very weak.

Conclusions. Our results suggest that the contribution of core-collapse supernovae from massive stars to the solar (and Galactic) p-nuclei has been underestimated in the past, and more specifically, that the contribution from massive stars with sub-solar metallicities may even dominate. A more detailed study including stellar models with a wide range of masses and metallicities remains to be performed, together with a quantitative analysis that is based on the chemical evolution of the Galaxy.

Citation

Choplin, A., Goriely, S., Hirschi, R., Tominaga, N., & Meynet, G. (2022). The p-process in exploding rotating massive stars. Astronomy & Astrophysics, 661, Article A86. https://doi.org/10.1051/0004-6361/202243331

• Journal Article Type: Article
• Acceptance Date: Mar 25, 2022
• Publication Date: May 5, 2022
• Journal: Astronomy & Astrophysics
• Print ISSN: 0004-6361
• Publisher: EDP Sciences
• Peer Reviewed: Peer Reviewed
• Volume: 661
• Article Number: A86
• DOI: https://doi.org/10.1051/0004-6361/202243331
• Keywords: stars: massive / stars: rotation / stars: interiors / stars: abundances / nuclear reactions, nucleosynthesis, abundances
• Publisher URL: https://www.aanda.org/articles/aa/full_html/2022/05/aa43331-22/aa43331-22.html