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arXiv · 1910.11401

Stellar Pulsation and the Production of Dust and Molecules in Galactic Carbon Stars

Kathleen E. Kraemer·G. C. Sloan·Luke D. Keller·Iain McDonald·Albert A. Zijlstra·Martin A. T. Groenewegen
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Abstract

New infrared spectra of 33 Galactic carbon stars from FORCAST on SOFIA reveal strong connections between stellar pulsations and the dust and molecular chemistry in their circumstellar shells. A sharp boundary in overall dust content, which predominantly measures the amount of amorphous carbon, separates the semi-regular and Mira variables, with the semi-regulars showing little dust in their spectra and the Miras showing more. In semi-regulars, the contribution from SiC dust increases rapidly as the overall dust content grows, but in Miras, the SiC dust feature grows weaker as more dust is added. A similar dichotomy is found with the absorption band from CS at $\sim$7.3 $\mu$m, which is generally limited to semi-regular variables. Observationally, these differences make it straightforward to distinguish semi-regular and Mira variables spectroscopically without the need for long-term photometric observations or knowledge of their distances. The rapid onset of strong SiC emission in Galactic carbon stars in semi-regulars variables points to a different dust-condensation process before strong pulsations take over. The break in the production of amorphous carbon between semi-regulars and Miras seen in the Galactic sample is also evident in Magellanic carbon stars, linking strong pulsations in carbon stars to the strong mass-loss rates which will end their lives as stars across a wide range of metallicities.

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Kathleen E. Kraemer, G. C. Sloan, Luke D. Keller, Iain McDonald, Albert A. Zijlstra, Martin A. T. Groenewegen. 2019-10-24. Stellar Pulsation and the Production of Dust and Molecules in Galactic Carbon Stars. https://doi.org/10.3847/1538-4357%2Fab4f6b

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