Molecular line observations of the carbon-rich circumstellar envelope cit6 at 7mm wavelengths

Abstract

We present a λ7mm spectral line survey of the carbon-rich circumstellar envelope (CSE) CIT6 using the 45m telescope at the Nobeyama Radio Observatory. A total of 25 spectral features belonging to five molecular species (HC3N, HC5N, HC7N, SiO, and CS) are detected, enabling us to investigate the chemistry of cyanopolyyne chains. The line strengths are compared with those of the proto-typical carbon-rich CSE IRC+10216. The results show that the cyanopolyyne molecules are enhanced in CIT6, suggesting that it is more evolved than IRC+10216. In order to investigate the structure of CIT6, we have constructed a three-dimensional spatiokinematic model. By comparing the observed line profiles with the models, we conclude that this envelope is asymmetric and is composed of several incomplete shells. © 2012. The American Astronomical Society. All rights reserved.