IRC +10216 is the prototypical  carbon star exhibiting an extended molecular circumstellar envelope. Its  spectral properties are therefore the template for an entire class of  objects. So far, the 1.3 cm wavelength (e.g. radio "K" band) is still  not explored in an unbiased view. Therefore, we carried out a spectral  line survey with the Effelsberg-100 m telescope toward IRC +10216 to  study its 1.3 cm spectral line characteristics. In the circumstellar  shell of IRC +10216, we find 78 spectral lines, among which 12 remain  unidentified (Overview of the 1.3 cm line survey is displayed in Fig.  1.). The identified lines are assigned to 18 different molecules and  radicals. A total of 23 lines from species known to exist in this  envelope are detected for the first time outside the solar system and  there are additional 20 lines first detected in IRC +10216. The  potential orgin of "U" lines is also discussed. Assuming local  thermodynamic equilibrium (LTE), we then determine rotational  temperatures and column densities of 17 detected molecules. Molecular  abundances relative to H2 are also estimated. A non-LTE analysis of NH3  shows that the bulk of its emission arises from the inner envelope with a  kinetic temperature of 70 ± 20 K. Evidence for NH3 emitting gas with  higher kinetic temperature is also obtained, and potential abundance  differences between various 13C-bearing isotopologues of HC5N are  evaluated. Overall, the isotopic 12C/13C ratio is estimated to be 49 ±  9. Finally, a comparison of detected molecules in the 1.3 cm wavelength  with the dark cloud TMC-1 indicates that silicate-bearing molecules are  more predominant in IRC +10216. 

  This  work by Yan Gong, Christian Henkel, Silvia Spezzano, Sven Thorwirth,  Karl M. Menten, Friedrich Wyrowski, Ruiqing Mao, and Bernd Klein has  been published in the Astronomy and Astrophysics. The detailed  information can be found in http://adsabs.harvard.edu/abs/2015A%26A.574A.56G 

By with GONG Yan 

    Fig  1. Comparison of the column densities and rotational temperatures of  different molecules. The labels for column densities are blue on the  left side, while those for rotational temperatures are red on the right  side. Here, a Trot of 39.1 K has been taken for para and ortho NH3 (see  Sect. 4.1 and Table 4).