The spectra of evolved stars at 20--25\,GHz: tracing circumstellar chemistry during the asymptotic giant branch to planetary nebula transition

Abstract

We report an unbiased radio line survey towards the circumstellar envelopes of evolved stars at the frequency range from 20 to 25 GHz, aiming to obtain a more complete unbiased picture of the chemical evolution in the final stages of stellar evolution. The observation sample includes the asymptotic giant branch (AGB) star IRC+10216, the proto-planetary nebulae (PPNs) CRL\,2688 and CRL\,618, and the young planetary nebula (PN) NGC\,7027, representing an evolutionary sequence spanning about 10,000 years. Rotational transitions from cyanopolyyne chains and inversion lines from ammonia are detected in the AGB star and PPNs, while the PN displays several recombination lines. The different spectral behaviors of these evolved stars clearly reflect the evolution of circumstellar chemistry during the AGB-PPN-PN transitions.

37 pages. 8 figures, Accepted for publication in PASJ

References in corpus (6)

• A spectral line survey in the 2 mm and 1.3 mm windows toward the carbon rich envelope of IRC +10216
• A spectral line survey of NGC 7027 at millimeter wavelengths
• A 1.3 cm line survey toward IRC +10216
• A molecular line survey of the extreme carbon star CRL 3068 at millimeter wavelengths
• A spectral line survey of IRC +10216 between 13.3 and 18.5 GHz
• Shock-enhanced ammonia emission in the Egg nebula

Cited by in corpus (2)

• Molecules in the carbon-rich protoplanetary nebula CRL 2688
• A 3 mm Molecular Line Survey toward The C-star Envelope CIT 6