SIMBAD references

1994A&A...285..247B - Astronomy and Astrophysics, volume 285, 247-271 (1994/5-1)

Molecular observations of O- and C-rich circumstellar envelopes.


Abstract (from CDS):

We present observations of 10 microwave transitions of the molecules SiO, HCN, HNC, SiS, HC3N, CS, SO, and 13CO in a total sample of 47 evolved stars. The studied sources are mainly O- and C-rich standard AGB stars, as well as O-rich red supergiants, S-type stars, protoplanetary nebulae and detached envelopes. We also take into account observations of these transitions, as well as of 12CO J=1-0, from the literature. We find that the molecules can be classified as "O-like" (SiO and SO) and "C-like" (HCN, HNC, SiS, HC3N and CS). The emission of O-like molecules is significantly stronger in O-rich stars than in C-rich sources, and the opposite holds for C-like species. The behaviour of 12CO and 13CO is found to be intermediate between those of O-/C-like species. We have estimated the molecular abundances in most of the studied objects. Our results indicate that the abundance of the carbon-bearing molecules HCN, HNC and CS in O-rich circumstellar envelopes can only be explained assuming the presence of an active photochemistry in their outer layers. In other cases, such as HCN and CS in C-rich AGB stars, the derived abundances are compatible with LTE chemical models. The SiO and SiS abundances in O-rich and C-rich standard sources can also be explained by LTE chemistry if we assume moreover some depletion onto grains. We finally discuss the chemical properties of some individual interesting sources.

Abstract Copyright:

Journal keyword(s): stars: abundances - stars: circumstellar matter - stars: late type - stars: AGB, post-AGB - radio lines: stars

VizieR on-line data: <Available at CDS (J/A+A/285/247): tables 3,4,5,6,7,8>

Simbad objects: 47

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