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S19B0063abst

S19B0063

We propose to make COMICS N-band low-resolution spectroscopic observations of red giants that are less evolved, but with significant mid-infrared excess. Their COMICS spectra are essential to prove that their mid-infrared excess is from circumstellar dust and not from plasma free-free emission, emission from shells of molecular gas (i.e., MOLsphere), nor extremely large silicate grains, and also to determine the species and quantity of the dust formed. Current understanding of dust production in the envelopes of red giants involves stellar pulsation that generates shock waves running through the star’s atmosphere, creating conditions of pressure and temperature suitable for dust formation. However, less evolved red giants are not in general large amplitude pulsators. This fact issues a challenge to the current understanding of dust production. How non-variable less evolved red giants can form dust? How much and what kind of dust do they form? The proposed observational study will address these questions.

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