A spectral line survey in the 2 mm and 1.3 mm windows toward the carbon rich envelope of IRC +10216

TL;DR

This spectral line survey of IRC +10216 in the 2 mm and 1.3 mm bands detected 377 lines, identified most molecules, and provided new isotopic and spectroscopic data, enhancing understanding of this carbon-rich star's envelope.

Contribution

First detection of isotopomers 13CCH and HN13C in IRC +10216, and improved spectroscopic parameters for several molecules, advancing molecular knowledge of this star's envelope.

Findings

Detected 377 spectral lines, 360 assigned to known molecules.

First detection of 13CCH and HN13C isotopomers in IRC +10216.

Confirmed formaldehyde presence and reported isotopic abundance differences.

Abstract

We present the results of our spectral line surveys in the 2 mm and 1.3 mm windows toward the carbon rich envelope of IRC +10216. Totally 377 lines are detected, among which 360 lines are assigned to 57 known molecules (including 29 rare isotopomers and 2 cyclic isomers). Only 17 weak lines remain unidentified. Rotational lines of isotopomers 13CCH and HN13C are detected for the first time in IRC +10216. The detection of the formaldehyde lines in this star is also confirmed. Possible abundance difference among the three 13C substituted isotopic isomers of HC3N is reported. Isotopic ratios of C and O are confirmed to be non-solar while those of S and Si to be nearly solar. Column densities have been estimated for 15 molecular species. Modified spectroscopic parameters have been calculated for NaCN, Na13CN, KCN and SiC2. Transition frequencies from the present observations were used to improve the spectroscopic parameters of Si13CC, 29SiC2 and 30SiC2.