Small Carbon Chains In Circumstellar Envelopes

Observations were made of a number of carbon-rich circumstellar envelopes using the Phoenix spectrograph on the Gemini South telescope to determine the presence of small carbon chain molecules. The circumstellar envelope of IRC+10216 (CRL 1381) has been extensively studied, due to its brightness in the infrared, and \chem{C_3} and \chem{C_5} have previously been observed\footnote{Hinkle, K.W., Keady, J.J., \& Bernath, P.F. 1988, \textit{Science}, 241, 1319}\footnote{Bernath, P.F., Hinkle, K.H., \& Keady, J.J. 1989, \textit{Science}, 244, 562}. Vibration-rotation lines of the \nub{3} antisymmetric stretch of \chem{C_3} near 2040 \wn have been used to determine the column density of \chem{C_3} in three new circumstellar envelopes: CRL 865, CRL 1922 and CRL 2023. Our new observations support the column density determined from CRL 1381 and also demonstrate that \chem{C_3} is common in carbon-rich circumstellar shells. We additionally determine upper limits for the small carbon chains, \chem{C_5} and \chem{C_7}