Full computation of massive AGB evolution. II. The role of mass loss and cross-sections

TL;DR

This study investigates how uncertainties in nuclear reaction rates and mass loss affect the modeling of intermediate-mass star evolution during the AGB phase, highlighting the impact on chemical yields and the role of these stars in globular cluster pollution.

Contribution

It provides a comprehensive analysis of the effects of different nuclear cross-sections and mass loss rates on AGB star evolution and nucleosynthesis, emphasizing the uncertainties in predictive modeling.

Findings

Na23 nucleosynthesis is more efficient with NACRE cross-sections.

Magnesium isotope ratios vary with different nuclear data.

C+N+O remains roughly constant despite model uncertainties.

Abstract

In the course of a systematic exploration of the uncertainties associated to the input micro- and macro-physics in the modeling of the evolution of intermediate mass stars during their Asymptotic Giant Branch (AGB) phase, we focus on the role of the nuclear reactions rates and mass loss. We consider masses 3<M/Msun<6.5 for a metallicity typical for Globular Cluster, Z=0.001, and compare the results obtained by computing the full nucleosynthesis with hot bottom burning (HBB), for a network of 30 elements, using either the NACRE or the Cameron & Fowler (1988) cross-sections. The results differ in particular with respect to the Na23 nucleosynthesis (which is more efficient in the NACRE case) and the magnesium isotopes ratios. For both choices, however, the CNO nucleosynthesis shows that the C+N+O is constant within a factor of two, in our models employing a very efficient convection treatment. Different mass loss rates alter the physical conditions for HBB and the length of the AGB phase, changing indirectly the chemical yields. These computations show that the predictive power of our AGB models is undermined by these uncertainties. In particular, it appears at the moment very difficult to strongly accept or dismiss that these sources play a key-role in the pollution of Globular Clusters (GCs)