Dust Production in Galactic & Magellanic Carbon Stars
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Kathleen Kraemer
Boston College
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New SOFIA/FORCAST spectra of Galactic carbon stars have revealed strong ties between the stellar pulsations that these stars are undergoing and the dust and molecular gas that surround them. A fundamental issue in stellar astrophysics is the role such evolved low- and  intermediate-mass stars play in the chemical enrichment of the Universe. Carbon stars, asymptotic giant branch stars where the C/O ratio is >1, may be the dominant source of dust contributed by stars back into the ISM. Recent studies of carbon stars, though, have concentrated on the metal-poor Magellanic Clouds, as the Galactic studies were hampered by limited samples and unknown distances. To address this, we observed 33 Galactic carbon stars with FORCAST, focusing on underrepresented types, the semi-regular variables (SRVs) and longest-period Miras. We find that the Miras, with their strong pulsations, are producing substantial amounts of amorphous carbon dust. The SRVs, on the other hand, show much less dust, and most of that is silicon carbide (SiC). The molecular gas also shows sharp distinctions between the Miras and the SRVs. We discuss these findings and compare them to the dust and gas seen around Magellanic carbon stars.

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