Understanding the mass-loss process of evolved Sun-like stars using high-angular-resolution observations

Research Project, 2020 – 2023

Stars with masses between roughly one and eight solar masses go through the asymptotic giant branch (AGB) phase at the end of their lives. During the AGB phase, they present strong mass loss that has an important effect on the evolution of the individual stars and also on the chemical evolution of galaxies. The widely-accepted paradigm for the mass-loss process consists of a two-step process. First, stellar convections and pulsations lift material to high distances in the atmosphere where dust can form. Then, radiation pressure acting on the newly-formed dust grains drives the outflow. It is not possible to predict the mass-loss rate of a given star from first principles, however, because of our poor knowledge of many important details, such as convective motions in the envelope, pulsations, and the dust formation process.The goal of this research proposal is to advance our understanding of the processes that cause the mass loss. This will be done by using the exquisite capabilities of instruments that can spatially-resolve the dust formation region, and even the stellar photospheres, of close-by AGB stars. The observations allow for studies to be carried out in unprecedented detail. The results will provide important constraints to theoretical models, such as the density, temperature, and velocity distributions of the gas and the size and distribution of the dust grains in the innermost regions, paving the way to a quantitative understanding of the AGB mass-loss process.