Impact of the uncertainty in α-captures on 22Ne on the weak s-process in massive stars

Nishimura, N.; Hirschi, R.; Pignatari, M.; Herwig, F.; Beard, M.; Imbriani, G.; Görres, J.; Deboer, R. J.; Wiescher, M.

Abstract

Massive stars at solar metallicity contribute to the production of heavy elements with atomic masses between A = 60 and A = 90 via the so-called weak s-process (which takes place during core He and shell C burning phases). Furthermore, recent studies have shown that rotation boosts the s-process production in massive stars at low metallicities, with a production that may reach the barium neutron-magic peak. These results are very sensitive to neutron source and neutron poison reaction rates. For the weak s-process, the main neutron source is the reaction 22Ne(α,n)25Mg, which is in competition with 22Ne(α,γ)26Mg. The uncertainty of both rates strongly affects the nucleosynthesis predictions from stellar model calculations. In this study, we investigate the impact of the uncertainty in α-captures on 22Ne on the s-process nucleosynthesis in massive stars both at solar and at very low metallicity. For this purpose, we post-process, with the Nugrid mppnp code, non-rotating and rotating evolutionary models 25M ⊙ stars at two different metallicities: Z = Z ⊙ and Z = 10 -5 Z ⊙ , respectively. Our results show that uncertainty of 22Ne(α,n)25Mg and 22Ne(α,γ)26Mg rates have a significant impact on the final elemental production especially for metal poor rotating models. Beside uncertainties in the neutron source reactions, for fast rotating massive stars at low metallicity we revisit the impact of the neutron poisoning effect by the reaction chain 16 O(n,γ) 17 O(α, γ)21Ne, in competition with the 17 O(α,n)20Ne, recycling the neutrons captured by 16 O. © 2014 AIP Publishing LLC.

Citation

Nishimura, N., Hirschi, R., Pignatari, M., Herwig, F., Beard, M., Imbriani, G., Görres, J., Deboer, R. J., & Wiescher, M. Impact of the uncertainty in α-captures on 22Ne on the weak s-process in massive stars. Presented at ORIGIN OF MATTER AND EVOLUTION OF GALAXIES 2013: Proceedings of the 12th International Symposium on Origin of Matter and Evolution of Galaxies (OMEG12), Tsukuba, Japan

• Presentation Conference Type: Conference Paper (published)
• Conference Name: ORIGIN OF MATTER AND EVOLUTION OF GALAXIES 2013: Proceedings of the 12th International Symposium on Origin of Matter and Evolution of Galaxies (OMEG12)
• Acceptance Date: Jun 1, 2014
• Publication Date: Jan 1, 2014
• Deposit Date: Jun 29, 2018
• Journal: AIP Conference Proceedings
• Print ISSN: 0094-243X
• Publisher: American Institute of Physics
• Peer Reviewed: Peer Reviewed
• Volume: 1594
• Issue: 1
• Pages: 146-151
• ISBN: 9780735412286
• DOI: https://doi.org/10.1063/1.4874059
• Public URL: https://hull-repository.worktribe.com/output/561313
• Publisher URL: https://aip.scitation.org/doi/abs/10.1063/1.4874059