Speaker
Description
The asymptotic giant branch (AGB) is a late evolutionary stage of stars with masses between 0.8-8 solar masses. AGB stars have grown to radii of around 300 times their original sizes, have non-spherically symmetric surfaces, immense convection zones, and strong dust-driven winds that are initiated when dense dust clouds form in regions close to the stellar surface. These winds are important for the transport of newly formed elements from the stellar interior to the interstellar medium.
We translate models of a 1 solar mass oxygen-rich AGB star, and its dust-driven wind, from time dependent 3D radiation-hydrodynamical simulations with CO5BOLD, into the input for radiative transfer computations with RADMC-3D, to create time dependent synthetic observables. A major goal is to simulate observable effects due to non-spherical structures and clumpy dust formation, primarily at the visual and near-infrared wavelength regimes. Here, we prioritise images at 10um to capture emission from Mg2SiO4 dust.
We find that optical interferometry with VLTI/MATISSE, would be able to detect emission from dust clouds in the vicinity of O-rich AGB stars within distances of around 500 pc. Dust formation is common, but sporadic, and one can expect observable dust clouds to appear within 5 Rstar above the stellar surface with a periodicity of as low as 2 yrs, or as long as several decades. This period and the detection probability depend on the dust formation efficiency of the star, which is also connected to the star's mass loss rate. Finally, we find that low mass-loss rate stars, where almost no dust-driven wind is expected, can still produce temporary and localised gusts of such winds that, in large spatial and time scales, appear as a spherically symmetric and sustained wind.