New Asymptotic Giant Branch models for a range of metallicities

TL;DR

This paper introduces a comprehensive grid of new stellar models for the Asymptotic Giant Branch across various metallicities, incorporating detailed physics like carbon-enhancement and mass loss, to improve understanding of AGB star evolution.

Contribution

The authors present the most extensive set of AGB models to date, with consistent treatment of carbon-enhancement, updated opacities, and inclusion of post-AGB phases, advancing stellar evolution modeling.

Findings

Models agree with previous synthetic models on effective temperatures.

Good match with empirical carbon-star lifetimes.

Extended models into post-AGB phase for certain masses.

Abstract

We present a new grid of stellar model calculations for stars on the Asymptotic Giant Branch between 1.0 and 6.0 M_sun. Our grid consists of 5 chemical mixtures between Z=0.0005 and Z=0.04, with both solar-like and $\alpha$-element enhanced metal ratios. We treat consistently the carbon-enhancement of the stellar envelopes by using opacity tables with varying C/O-ratio and by employing theoretical mass loss rates for carbon stars. The low temperature opacities have been calculated specifically for this project. For oxygen stars we use an empirical mass loss formalism. The third dredge-up is naturally obtained by including convective overshooting. Our models reach effective temperatures in agreement with earlier synthetic models, which included approximative carbon-enriched molecular opacities and show good agreement with empirically determined carbon-star lifetimes. A fraction of the models could be followed into the post-AGB phase, for which we provide models in a mass range supplementing previous post-AGB calculations. Our grid constitutes the most extensive set of AGB-models, calculated with the latest physical input data and treating carbon-enhancement due to the third dredge-up most consistently.