First models of the s process in AGB stars of solar metallicity for the stellar evolutionary code ATON with a novel stable explicit numerical solver

Yagüe López, A.; García-Hernández, D. A.; Ventura, P.; Doherty, C. L.; den Hartogh, J. W.; Jones, S. W.; Lugaro, M.
Bibliographical reference

Astronomy and Astrophysics

Advertised on:
1
2022
Number of authors
7
IAC number of authors
1
Citations
4
Refereed citations
4
Description

Aims: We describe the first s-process post-processing models for asymptotic giant branch (AGB) stars of masses 3, 4, and 5 M⊙ at solar metallicity (Z = 0.018) computed using the input from the stellar evolutionary code ATON.
Methods: The models are computed with the new code SNUPPAT (S-process NUcleosynthesis Post-Processing code for ATON), which includes an advective scheme for the convective overshoot that leads to the formation of the main neutron source, 13C. Each model is post-processed with three different values of the free overshoot parameter. Included in the code SNUPPAT is the novel Patankar-Euler-Deflhard explicit numerical solver, which we use to solve the nuclear network system of differential equations.
Results: The results are compared to those from other s-process nucleosynthesis codes (Monash, FRUITY, and NuGrid), as well as observations of s-process enhancement in AGB stars, planetary nebulae, and barium stars. This comparison shows that the relatively high abundance of 12C in the He-rich intershell in ATON results in an s-process abundance pattern that favours the second over the first s-process peak for all the masses explored. Also, our choice of an advective as opposed to a diffusive numerical scheme for the convective overshoot results in significant s-process nucleosynthesis for the 5 M⊙ models as well, which may be in contradiction with observations.
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Nucleosynthesis and molecular processes in the late stages of Stellar Evolution
Low- to intermediate-mass (M < 8 solar masses, Ms) stars represent the majority of stars in the Cosmos. They finish their lives on the Asymptotic Giant Branch (AGB) - just before they form planetary nebulae (PNe) - where they experience complex nucleosynthetic and molecular processes. AGB stars are important contributors to the enrichment of the
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