Modeling extinction and reddening effects by radiative torque disruption of dust grains in the Betelgeuse envelope

Dust is believed to form in the circumstellar envelope around the Asymptotic Giant Branch (AGB) and Red Supergiant (RSG) stars. The formation and evolution of circumstellar dust could be affected by the radiative and mechanical feedback. In this poster, we showed that the intense radiation from evolved stars could modify the grain-size distribution through the RAdiative Torque Disruption (RATD) mechanism. Then we modelled the extinction curve of the Betelgeuse envelope as a case study. Our model showed that the extinction decreases at near-UV, optical, and infrared wavelengths while increasing at far-UV wavelengths due to the abundance of small grains produced by the RATD mechanism. The consequent flux well reproduced the observations from the near-UV to near-IR range, which suggested the scenario of driving stellar winds by smaller grains a < 0.1 um. Our model can be used to explain dust extinction and reddening in other RSG/AGB spectra.