2023•Frontiers in Astronomy and Space SciencesOpen access
Photochemical origin of SiC2 in the circumstellar envelope of carbon-rich AGB stars revealed by ALMA
Yanan Feng, Xiaohu Li, Tom J. Millar, R. Szczerba, Ke Wang, Donghui Quan, Sheng‐Li Qin, Xuan Fang, Juan Tuo, Zhenzhen Miao, Rong Ma, Fengwei Xu, Jingfei Sun, Biwei Jiang, Qiang Chang, Jianchao Yang, Gao‐Lei Hou, Fangfang Li, Yong Zhang
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Abstract
The fact that whether SiC2 is a parent species, formed in the photosphere or as a by-product of high-temperature dust formation, or a daughter species, formed in chemistry driven by the photodestruction of the parent species in the outer envelope, has been debated for a long time. In this study, we analyze the Atacama Large Millimeter Array (ALMA) observations of four SiC2 transitions in the circumstellar envelopes (CSEs) of three C-rich asymptotic giant branch (AGB) stars (AI Vol, II Lup, and RAFGL 4211) and find that SiC2 exhibits an annular, shell-like distribution in these targets, suggesting that SiC2 can be a daughter species in the CSEs of carbon-rich AGB stars. The results may provide important references for future chemical models.
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