Impact of the latest 22Ne+α reaction rates on nucleosynthesis in massive stars and galactic chemical evolution
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arXiv
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| Natura: | Preprint |
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2025
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| author | Kotar, Emma Ota, Shuya Dewey, Allyson Millman, Joshua Roberti, Lorenzo Pignatari, Marco |
| author_facet | Kotar, Emma Ota, Shuya Dewey, Allyson Millman, Joshua Roberti, Lorenzo Pignatari, Marco |
| contents | In massive stars (initial mass of > 9 solar masses), the weak s (slow neutron capture) process produces elements between Fe and Zr, enriching the Galaxy with these elements through core-collapse supernova explosions. The weak s-process nucleosynthesis is driven by neutrons produced in the 22Ne(α, n)25Mg reaction during convective He-core and C-shell burning. The yields of heavy elements thus depend on the 22Ne(α, n)25Mg and the competitive 22Ne(α, γ)26Mg reaction rates which are dominated by several narrow-resonance reactions. While the accuracy of these rates has been under debate for decades, recent experimental efforts, including ours, drastically reduced these uncertainties. In this work, we use a set of 280 massive star nucleosynthesis models calculated using different 22Ne(α, n)25Mg and 22Ne(α, γ)26Mg rates, and a galactic chemical evolution (GCE) study to probe their impact on the weak s-process elemental abundances in the Galaxy. The GCE was computed with the OMEGA+ code, using the new sets of stellar yields with different 22Ne+α rates. From GCE, we find that these rates are causing up to 0.45 dex of variations in the [Cu/Fe], [Ga/Fe], and [Ge/Fe] ratios predicted at solar metallicity. The greatest impact on the stellar nucleosynthesis and GCE results derives from uncertainties in the (α,n) strength (ωγ(α,n)) of the Ex=11.32 MeV resonance. We show that the variations observed in the GCE calculations for the weak s-proess elements become negligibly smaller than dispersions found in observations once the ωγ(α,n) is accurately determined within the uncertaintiy of 10 to 20% (typically reported experimental errors for the resonance) in future nuclear physics experiments. |
| format | Preprint |
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arxiv_https___arxiv_org_abs_2509_19583 |
| institution | arXiv |
| publishDate | 2025 |
| record_format | arxiv |
| spellingShingle | Impact of the latest 22Ne+α reaction rates on nucleosynthesis in massive stars and galactic chemical evolution Kotar, Emma Ota, Shuya Dewey, Allyson Millman, Joshua Roberti, Lorenzo Pignatari, Marco Solar and Stellar Astrophysics In massive stars (initial mass of > 9 solar masses), the weak s (slow neutron capture) process produces elements between Fe and Zr, enriching the Galaxy with these elements through core-collapse supernova explosions. The weak s-process nucleosynthesis is driven by neutrons produced in the 22Ne(α, n)25Mg reaction during convective He-core and C-shell burning. The yields of heavy elements thus depend on the 22Ne(α, n)25Mg and the competitive 22Ne(α, γ)26Mg reaction rates which are dominated by several narrow-resonance reactions. While the accuracy of these rates has been under debate for decades, recent experimental efforts, including ours, drastically reduced these uncertainties. In this work, we use a set of 280 massive star nucleosynthesis models calculated using different 22Ne(α, n)25Mg and 22Ne(α, γ)26Mg rates, and a galactic chemical evolution (GCE) study to probe their impact on the weak s-process elemental abundances in the Galaxy. The GCE was computed with the OMEGA+ code, using the new sets of stellar yields with different 22Ne+α rates. From GCE, we find that these rates are causing up to 0.45 dex of variations in the [Cu/Fe], [Ga/Fe], and [Ge/Fe] ratios predicted at solar metallicity. The greatest impact on the stellar nucleosynthesis and GCE results derives from uncertainties in the (α,n) strength (ωγ(α,n)) of the Ex=11.32 MeV resonance. We show that the variations observed in the GCE calculations for the weak s-proess elements become negligibly smaller than dispersions found in observations once the ωγ(α,n) is accurately determined within the uncertaintiy of 10 to 20% (typically reported experimental errors for the resonance) in future nuclear physics experiments. |
| title | Impact of the latest 22Ne+α reaction rates on nucleosynthesis in massive stars and galactic chemical evolution |
| topic | Solar and Stellar Astrophysics |
| url | https://arxiv.org/abs/2509.19583 |