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A radio molecular line search for evidence of an O-rich environment around binary in silicate carbon stars

Zhao, Z, Chen, X, Ellingsen, SP ORCID: 0000-0002-1363-5457, Sobolev, AM and Ouyang, X 2020 , 'A radio molecular line search for evidence of an O-rich environment around binary in silicate carbon stars' , Astrophysical Journal, vol. 890, no. 1 , pp. 1-11 , doi: 10.3847/1538-4357/ab6594.

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We report observations of oxygen-rich (O-rich) radio molecular line tracers, including H2CO, H2O, and HCO+ toward 28 silicate carbon stars (SCSs). SCSs are special evolved star systems that consist of a carbon star associated with peculiar O-rich circumstellar material. Absorption in the 6 cm H2CO transition was detected from seven SCSs using the Shanghai 65 m Tianma radio telescope. In order to further investigate their O-rich material, several 3 mm molecular lines including HCO+ and CO were also observed with the Purple Mountain Observatory 13.7 m telescope. Double-peak profiles in some of these lines suggest the possible presence of a companion in the SCS system. A negative association between H2O masers and H2CO absorption was found in our sample of SCSs. The H2O maser sources may correspond to an earlier evolutionary stage when the circumstellar envelope (CSE) material is O-rich and limited to a compact and denser region. As the star evolves the CSE gradually expands and carbon abundance is enhanced, resulting in the H2O masers disappearing and H2CO absorption arising.

Item Type: Article
Authors/Creators:Zhao, Z and Chen, X and Ellingsen, SP and Sobolev, AM and Ouyang, X
Keywords: evolved stars, silicon stars, circumstellar envelopes, circumstellar matter, binary stars, asymptotic giant branch stars, post-asymptotic giant branch stars, carbon stars, chemically peculiar stars
Journal or Publication Title: Astrophysical Journal
Publisher: Univ Chicago Press
ISSN: 0004-637X
DOI / ID Number: 10.3847/1538-4357/ab6594
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Copyright 2020 The American Astronomical Society

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