Discovery of methyl silane and confirmation of silyl cyanide in IRC +10216

J. Cernicharo , M. Agúndez , L. Velilla Prieto , M. Guélin , J. R. Pardo , C. Kahane (1) , C. Marka , C. Kramer , S. Navarro , G. Quintana-Lacaci , J. P. Fonfría , N. Marcelino , B. Tercero , E. Moreno , S. Massalkhi , M. Santander-García , M. C. Mccarthy , C. A. Gottlieb , J. L. Alonso

1 IPAG - Institut de Planétologie et d'Astrophysique de Grenoble

We report the discovery in space of methyl silane, CH₃SiH₃, from observations of ten rotational transitions between 80 and 350 GHz (J_u from 4 to 16) with the IRAM 30 m radio telescope. The molecule was observed in the envelope of the C-star IRC +10216. The observed profiles and our models for the expected emission of methyl silane suggest that the it is formed in the inner zones of the circumstellar envelope, 1-40 R_∗, with an abundance of (0.5-1) × 10^-8 relative to H₂. We also observed several rotational transitions of silyl cyanide (SiH₃CN), confirming its presence in IRC +10216 in particular, and in space in general. Our models indicate that silyl cyanide is also formed in the inner regions of the envelope, around 20 R_∗, with an abundance relative to H₂ of 6 × 10^-10. The possible formation mechanisms of both species are discussed. We also searched for related chemical species but only upper limits could be obtained.

This work was based on observations carried out with the IRAM 30-m telescope. IRAM is supported by INSU/CNRS (France), MPG (Germany), and IGN (Spain).

Keywords: stars: individual: IRC+10216; stars: carbon; astrochemistry; stars: AGB and post-AGB

Domains: Sciences of the Universe [physics]; Astrophysics [astro-ph]

J. Cernicharo, M. Agúndez, L. Velilla Prieto, M. Guélin, J. R. Pardo, et al.. Discovery of methyl silane and confirmation of silyl cyanide in IRC +10216. Astronomy and Astrophysics - A&A, 2017, 606, ⟨10.1051/0004-6361/201731672⟩. ⟨insu-03692477⟩