Full computation of massive AGB evolution. I. The large impact of convection on nucleosynthesis

TL;DR

This paper investigates how different models of convection in luminous AGB stars significantly influence nucleosynthesis outcomes, highlighting the importance of convection treatment in stellar evolution and chemical enrichment predictions.

Contribution

It provides detailed evolutionary calculations showing the impact of convection prescriptions on nucleosynthesis during the AGB phase, emphasizing the uncertainty's role in chemical yields.

Findings

Convection treatment drastically affects nucleosynthesis results.

Different convection models lead to varied chemical yields.

Uncertainties in convection influence predictions of stellar polluters.

Abstract

It is well appreciated that the description of overadiabatic convection affects the structure of the envelopes of luminous asymptotic giant branch (AGB) stars in the phase of ``hot bottom burning '' (HBB). We stress that this important uncertainty in the modeling plays a role which is much more dramatic than the role which can be ascribed, e.g., to the uncertainty in the nuclear cross-sections. Due to the role tentatively attributed today to the HBB nucleosynthesis as the site of self-enrichment of Globular Clusters stars, it is necessary to explore the difference in nucleosynthesis obtained by different prescriptions for convection. We present results of detailed evolutionary calculations of the evolution of stars of intermediate mass during the AGB phase. We follow carefully the nucleosynthesis at the base of the external convective region, showing that very different results can be obtained according to the presciption adopted to find out the temperature gradient within the instability regions. We discuss the uncertainties in the yields of the various chemical species and the role which these sources can play as polluters of the interstellar medium.