Outflows from asymptotic giant branch stars

Supervisor: Franz Kerschbaum (Department of Astrophysics) in collaboration with Josef Hron (Department of Astrophysics), Matthias Maercker (Chalmers University of Technology), and Sofia Ramstedt (Uppsala University)

Funding Situation: supervisor has secured funding

Project outline: For low-mass and intermediate-mass stars, mass loss (ML) on and shortly after the asymptotic giant branch (AGB) is a dominating factor in stellar evolution. The outflows show rich molecular chemistry and are formation sites of dust. ML plays a crucial role within the cosmic cycle of matter. Basic questions are still unanswered: What is the temporal evolution of the ML? What is the geometry of the ML? There is observational evidence that ML is varying with thermal pulses every 10.000+ years. High spatial resolution observations have shown thin detached shells, indicative of short phases of intense ML during thermal pulses, colliding with a previous, slower wind. Binarity further complicates outflows, and high spatial resolution observations of gas and dust (mm-CO, near-IR, far-IR) are needed to determine the morphology and evolution of ML. The PhD project will combine information on AGB outflows on different spatial scales. The high potential of IR spectro-interferometry has been demonstrated e.g. by observations of the atmospheric dynamics and granulation. We are partners in the new VLTI instrument MATISSE, which is powerful enough to image clumpiness of the outflows and co-spatiality of dust and gas emission. Our membership in the ALMA DEATHSTAR ACA Large Program consortium together with our Herschel GT material provides us with the multiscale observational picture. This project will combine observables and state-of-the-art model efforts to quantify the roles of AGB stars in stellar feedback. In turn, this provides essential inputs to studies of the evolution of interstellar gas and dust on galactic and extragalactic scales.