A molecular line survey of the extreme carbon star crl3068 at millimeter wavelengths

Abstract

We present the results of a molecular line survey of the extreme carbon star CRL3068. The observations were carried out with the Arizona Radio Observatory (ARO) 12m telescope and the Heinrich Hertz Submillimeter Telescope (SMT) at the λ 2mm and λ 1.3mm atmospheric windows. The observations cover the frequency bands from 130 to 162GHz and 219.5 to 267.5GHz. The typical sensitivities achieved are T R < 15mK and T R < 7mK for the ARO 12m and SMT, respectively. Seventy-two individual emission features belonging to 23 molecular species and isotopologues were detected. Only three faint lines remain unidentified. The species c-C 3H, CH 3CN, SiC 2, and the isotopologues, C 17O, C 18O, HC 15N, HN 13C, C 33S, C 34S, 13CS, 29SiS, and 30SiS are detected in this object for the first time. Rotational-diagram analysis is carried out to determine the column densities and excitation temperatures. The isotopic ratios of the elements C, N, O, S, and Si have also been estimated. The results are consistent with stellar CNO processing and suggest that CRL3068 is more carbon rich than IRC+10216 and CIT6. It is also shown that the chemical composition in CRL3068 is somewhat different from that in IRC+10216 with a more extensive synthesis of cyclic and long-chain molecules in CRL3068. The results will provide valuable clues for better understanding circumstellar chemistry © 2009 The American Astronomical Society.