ACES 1st evidence of correlation between angular sep's of high-frequency SiO masers from AGB stars
First evidence of a correlation between angular separations of high-frequency SiO masers from AGB stars and mass-loss rates
Bannawit Pimpanuwat
National Astronomical Research Institute of Thailand, Thailand
SiO masers are useful tracers for probing the inner circumstellar envelopes (CSEs) of evolved stars where convection and pulsation shocks are damped and dust formation commences (R ∼ a few R⋆). Here, we present results from ALMA Band 6 observations (213-270 GHz) of high-rotational
transition number J, J=5-4, 6-5, SiO masers towards oxygen-rich AGB stars, carried out as part of the ATOMIUM Large Programme (PI: L. Decin) in 2018-2020. We found evidence of a strong correlation between flux-weighted angular separation of maser components from the star and mass-loss rate based on linear regression models, with the correlation coefficients determined to be 0.50 (v=1, J=5-4), 0.85 (v=1, J=6-5) and 0.71 (v=2, J=5-4), all of which are commonly detected across the ATOMIUM sample. However, with limited 3D geometric considerations, it is impossible to rule out the possibility of the correlation existing by chance without multi-epoch
observations. We will test whether any de-projection techniques can be applied to determine the true separations of the maser components from the star and investigate how the locations of the masers may be related to the physio-chemical processes observed/predicted by wind models.
