S20A0118abst
S20A0118
Mass loss from stars in the last stages of life governs their ultimate destiny as a supernovae or PNe, and is crucial for galactic chemical enrichment. But the mechanisms driving the mass loss for these AGB stars remain poorly understood; to accelerate a dust-driven wind requires grains to form too close to the star, while aspheric and clumpy envelopes require some additional mechanism. Moreover, stellar pulsations also play a key role. Here we propose to directly image a) the pulsation-induced shocks formed in the outer atmospheres via their Hα emission, b) the dusty mass-loss shell directly surrounding (as close as 1.5 R⋆) the star and c) the extended mass-loss nebula. This is enabled via SCExAO’s unique capabilities: milliarcsecond-scale super-diffraction-limited imaging in differential polarisation and emission line wavelengths using VAMPIRES, and high-contrast, spectrally resolved imaging using CHARIS. By directly examining the mass-loss process at its source (the inner circumstellar environment), these powerful observations will yield critical insight into the mystery of the mass-loss process. Initial observations in S19A demonstrated excellent results, and here we propose to expand the program to a representative sample of stars, measure another point in the pulsation cycle.
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