AUTHOR=Feng Yanan , Li Xiaohu , Millar Tom J. , Szczerba Ryszard , Wang Ke , Quan Donghui , Qin Shengli , Fang Xuan , Tuo Juan , Miao Zhenzhen , Ma Rong , Xu Fengwei , Sun Jingfei , Jiang Biwei , Chang Qiang , Yang Jianchao , Hou Gao-Lei , Li Fangfang , Zhang Yong 

TITLE=Photochemical origin of SiC2 in the circumstellar envelope of carbon-rich AGB stars revealed by ALMA

JOURNAL=Frontiers in Astronomy and Space Sciences

VOLUME=10

YEAR=2023

URL=https://www.frontiersin.org/journals/astronomy-and-space-sciences/articles/10.3389/fspas.2023.1215642

DOI=10.3389/fspas.2023.1215642

ISSN=2296-987X

ABSTRACT=<p>The fact that whether SiC<sub>2</sub> 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 SiC<sub>2</sub> 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 SiC<sub>2</sub> exhibits an annular, shell-like distribution in these targets, suggesting that SiC<sub>2</sub> can be a daughter species in the CSEs of carbon-rich AGB stars. The results may provide important references for future chemical models.</p>