New Post-AGB star models as tools to understand AGB evolution and nucleosynthesis

TL;DR

This study uses new post-AGB star models and Gaia data to analyze stellar evolution, chemical enrichment, and nucleosynthesis, providing insights into different star classes and their evolutionary histories.

Contribution

The paper introduces new post-AGB models combined with Gaia data to better understand AGB evolution, nucleosynthesis, and the chemical history of individual stars.

Findings

Luminosity and surface carbon are key indicators of stellar history.

Different star classes can be distinguished based on chemical and luminosity data.

The approach offers new insights into debated aspects of AGB evolution.

Abstract

We study a sample of post-AGB stars in the Galaxy, with known surface chemical composition and s-process enrichment. The recent determination of the luminosities of these sources, based on Gaia parallaxes, allows for the fist time a deep investigation of Galactic post-AGB stars, with the possibility of characterising the individual objects in terms of mass, chemical composition and age of the progenitors. To this aim we used available evolutionary sequences of AGB stars, extended to the post-AGB phase, complemented by new models, specifically calculated for the present study. The combined knowledge of the surface carbon and of the luminosity proves the most valuable indicator of the previous history of the star, particularly for what regards the efficiency of the various mechanisms able to alter the surface chemical composition and the growth of the core mass. This kind of analysis allows dissecting different classes of stars, such as low-mass objects, that evolved as M-type stars for the whole AGB lifetime, carbon stars, massive AGB stars that experienced hot bottom burning. The potentialities of this approach to shed new light on still debated issues related to the AGB evolution are also commented.