A spectral line survey of IRC +10216 between 13.3 and 18.5 GHz^⋆

¹ CAS Key Laboratory for Research in Galaxies and Cosmology, Department of Astronomy, University of Science and Technology of China, Hefei 230026, PR China
e-mail: xyz1128@mail.ustc.edu.cn; zhuqf@ustc.edu.cn
² School of Astronomy and Space Science, University of Science and Technology of China, Hefei 230026, PR China
³ Department of Radio Science and Technology, Shanghai Astronomical observatory, 80 Nandan RD, Shanghai 200030, PR China
e-mail: lijuan@shao.ac.cn
⁴ Key Laboratory of Radio Astronomy, Chinese Academy of Sciences, PR China
⁵ Center for Astrophysics, Guangzhou University, Guangzhou 510006, PR China

Received: 16 March 2017
Accepted: 17 August 2017

Abstract

A spectral line survey of IRC +10216 between 13.3 and 18.5 GHz was carried out using the Shanghai Tian Ma 65 m Radio Telescope (TMRT-65 m) with a sensitivity of <7 mK. Thirty-five spectral lines of 12 different molecules and radicals were detected in total. Except for SiS, the detected molecules are all carbon-chain molecules, including HC₃N, HC₅N, HC₇N, HC₉N, C₆H, C₆H⁻, C₈H, SiC₂, SiC₄, c-C₃H₂, and l-C₅H. The presence of rich carbon-bearing molecules is consistent with the identity of IRC +10216 as a carbon-rich asymptotic giant branch (AGB) star. The excitation temperatures and column densities of the observed species are derived by assuming a local thermodynamic equilibrium and homogeneous conditions.