The Evolution of Stars with Variable Mass

Stellar evolution models are fundamental to modern astrophysics, providing critical insights into the life cycles of stars, the ages of star clusters and galaxies, nucleosynthesis, cosmic chemical evolution, and the prediction of phenomena such as supernovae and gravitational waves. However, these models are sensitive to uncertainties in mass-loss rates, particularly during late evolutionary phases including the asymptotic giant branch (AGB), during which the stellar evolution is driven by the star’s decreasing mass. We thus suffer significant challenges in modelling AGB stars due to the poorly constrained mass-loss rates, which critically influence the duration of the thermally pulsing phase. In this thesis, we focus on improving the modelling of AGB stars using the open-source stellar evolution code MESA. This allows us, and future researchers, to better constrain the dependence of thermal pulse properties on the variable stellar mass, which in turn is essential to constrain the contribution of AGB stars to galactic chemical evolution.