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

TL;DR

This paper introduces the first s-process nucleosynthesis models for AGB stars at solar metallicity using the ATON code with a novel explicit numerical solver, providing new insights into stellar element formation.

Contribution

It presents a new post-processing s-process model with an advective scheme and a novel explicit solver, improving the accuracy of nucleosynthesis predictions in AGB stars.

Findings

The models favor the second s-process peak due to high 12C abundance.

Advective overshoot scheme leads to significant s-process nucleosynthesis in 5 M models.

Comparison shows the models align with some observations but differ in s-process peak dominance.

Abstract

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), including an advective scheme for the convective overshoot that leads to the formation of the main neutron source, 13C. Each model is post-processed with 3 different values of the free overshoot parameter. Included in the code snuppat is the novel Patankar-Euler-Deflhard explicit numerical solver, that 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 of12C in the He-rich intershell in aton results in as-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 diffusive numerical scheme for the convective overshoot results in significants-process nucleosynthesis also for the 5 M models, which may be in contradiction with observations.