Weekly Astronomy Seminar - The evolution of DARWIN; the current status of wind models for AGB stars

Asymptotic giant branch (AGB) stars are luminous, cool giants with substantial mass loss. Dust formed in the stellar atmospheres plays a key role for the mass-loss mechanism: radial pulsations of the surface layers of the stars levitate material to distances where dust can form, which then is accelerated outward by radiation pressure. AGB stars are significant dust donors in the universe, feeding newly produced elements into the surrounding interstellar medium in the form of gas and dust through these stellar winds.

To model these dense outflows we use the DARWIN (Dynamic Atmosphere and Radiation-driven Wind models based on Implicit Numerics) code. The mass-loss process is modelled from first principles, with frequency-dependent radiation-hydrodynamics, and dust growth and evaporation. The DARWIN models have successfully been able produce outflows with dynamical and photometric properties compatible with observations, for both C-type and M-type AGB stars (e.g. Eriksson et al. 2014, Bladh et al. 2015). In this talk I will present the recent development in the DARWIN wind models: I will show results from a new large grid of M-type AGB star models, spanning a wide range in effective temperature, mass and lumiosity, as well as results from models for C-type AGB stars at low metallicities, compatible to those in LMC and SMC.