Small carbon chains in circumstellar envelopes

TL;DR

This study uses high-resolution spectroscopy to measure small carbon chain molecules in circumstellar envelopes, revealing potential discrepancies with existing chemical models and advancing understanding of carbon chemistry in stellar environments.

Contribution

First measurements of C$_{3}$ and C$_{5}$ in multiple circumstellar envelopes, providing data to refine models of carbon molecule formation around evolved stars.

Findings

Detected C$_{3}$ in four envelopes, including IRC +10216.

Estimated C$_{5}$ and C$_{7}$ in IRC +10216, setting upper limits for others.

Results suggest current chemical models may underestimate small carbon chain abundances.

Abstract

Observations were made for a number of carbon-rich circumstellar envelopes using the Phoenix spectrograph on the Gemini South telescope to determine the abundance of small carbon chain molecules. Vibration-rotation lines of the $\nu_{3}$ antisymmetric stretch of C$_{3}$ near 2040 cm$^{-1}$ (4.902 $\mu$m) have been used to determine the column density for four carbon-rich circumstellar envelopes: CRL 865, CRL 1922, CRL 2023 and IRC +10216. We additionally calculate the column density of C$_{5}$ for IRC +10216, and provide an upper limit for 5 more objects. An upper limit estimate for the C$_{7}$ column density is also provided for IRC+10216. A comparison of these column densities suggest a revision to current circumstellar chemical models may be needed.