| dc.description.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. | en_US |
