Ultra-deep 31.0-50.3 GHz spectral survey of IRC+10216

TL;DR

This ultra-deep spectral survey of IRC+10216 in the 31.0-50.3 GHz range reveals an extensive molecular inventory, including new species, providing detailed insights into the star's circumstellar chemistry and physical conditions.

Contribution

It presents the most sensitive Q-band spectral survey of IRC+10216, identifying numerous molecular transitions and discovering new species and vibrational modes.

Findings

Detected 652 spectral features from 81 species

Identified 713 transitions, with only 57 unknown lines

Provided detailed molecular and physical characterization of IRC+10216

Abstract

Context. IRC+10216, the carbon-rich envelope of the asymptotic giant branch (AGB) star CW Leo, is one of the richest molecular sources in the sky. Available spectral surveys below 51 GHz are more than 25 years old and new work is needed. Aims. Characterizing the rich molecular content of this source, specially for heavy species, requires to carry out very sensitive spectral surveys at low frequencies. In particular in this work we have achieved an rms in the range 0.2-0.6 mK per MHz. Methods. long Q-band (31.0-50.3 GHz) single dish integrations were carried out with the Yebes 40m telescope using specifically built receivers. State of the art line catalogs are used for line identification. Results. A total of 652 spectral features corresponding to 713 transitions from 81 species (we count as different the isomers, isotopologues and ortho/para species) are present in the data. Only 57 unidentified lines remain with signal to noise ratios >3. Some new species and/or vibrational modes have been discovered for the first time with this survey. Conclusions. This IRC+10216 spectral survey is, by far, the most sensitive one carried out to this date in the Q-band. It therefore provides the most complete view of IRC+10216 from 31.0 to 50.3 GHz, giving unique information on its molecular content, specially for heavy species. Rotational diagrams built from the data provide valuable information on the physical conditions and chemical content of this circumstellar envelope.