Modeling the impact of radiative feedback from a red supergiant on circumstellar dust

Abstract

Evolved stars (AGB and RSG stars) are one of the main sources of complex molecules and dust in the universe. They form dust by condensation of gas species in their circumstellar envelopes (CSEs). The extinction of the stellar light by circumstellar dust is vital for interpreting RSG/AGB observations and determining high mass RSG progenitors of core collapse supernovae. Nevertheless, circumstellar dust properties (size distribution and materials) are not well understood. Modern understanding of dust evolution suggests that intense stellar radiation can significantly impact the dust properties through the RAdiative Torque Disruption (RATD) mechanism. This thesis studies the impact of stellar radiation on circumstellar dust and model its e↵ects on the observational properties of RSGs. With the presence of the RATD mechanism, larger grains are disrupted into smaller species of size a < 0.5 µm. Consequently, the extinction increases at UV, optical, and IR wavelengths while decreasing at FUV wavelengths. The dust extinction model obtained with RATD was well-fitted with the Betelgeuse observed flux at UV-optical regimes and suggested the scenario of driving stellar winds by smaller grains a . 0.1 µm. Our works contributed to explaining dust extinction and circumstellar dust reddening in other RSG/AGB spectra. This leads to our further studies of interpreting observations of the VLT/SPHERE for extinction properties of circumstellar dust.