Observations of NH3, HC5N and HC7N toward AFGL 2688.
Abstract
The authors report new detections toward AFGL 2688 (Egg nebula) of a series of metastable (3,3), (4,4), (5,5) and non-metastable (3,2) transitions of NH3 as well as the cyanopolyyne HC5N (J = 8-7 and 9-8) and HC7N (J = 22-21) lines, using the 100-m Effelsberg telescope. Using an LTE model and combining the data with those of NH3 (1,1) and (2,2) and HC7N (J = 21-20) obtained previously, the authors derive the temperature and the density of the molecular envelopes. The ammonia and cyanopolyyne spectra are interpreted in terms of an optically-thick circumstellar disk and an optically-thin sphere, respectively. The HC5N and HC7N emissions are found to be ≡3 times more extended than that of NH3, in agreement with recent results of interferometric (VLA) mapping. The NH3 abundance is higher than that of HC5N and HC7N by one and two orders of magnitude, respectively.
- Publication:
-
Astronomy and Astrophysics
- Pub Date:
- June 1988
- Bibcode:
- 1988A&A...199..291T
- Keywords:
-
- Abundance;
- Interstellar Chemistry;
- Molecular Spectra;
- Nebulae;
- Stellar Composition;
- Stellar Envelopes;
- Ammonia;
- Cyano Compounds;
- Molecular Clouds;
- Radio Astronomy;
- Very Large Array (Vla);
- Astrophysics