Gas temperature distribution in the IRC + 10216 circumstellar envelope

We construct a simple model for the emission-line profiles of CO from the circumstellar envelope (CSE) of the carbon-rich star IRC +10216. Using the Sobolev approximation, and a given gas temperature distribution (gTD) we construct simulated observations of this source. We find that the 'canoni...

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Bibliographic Details
Published in:Monthly notices of the Royal Astronomical Society 1997-04, Vol.286 (4), p.1003-1011
Main Authors: Doty, Steven D., Leung, Chun Ming
Format: Article
Language:English
Subjects:
circumstellar matter
radio lines: general
stars: carbon
stars: evolution
stars: individual: IRC +10216
stars: mass-loss
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Summary:We construct a simple model for the emission-line profiles of CO from the circumstellar envelope (CSE) of the carbon-rich star IRC +10216. Using the Sobolev approximation, and a given gas temperature distribution (gTD) we construct simulated observations of this source. We find that the 'canonical' gTD [T(r)∝r.0.7] cannot reproduce the observations. Guided by a strong correlation between telescope beamsize and peak intensity, we vary the gTD to fit the observations, and find that the data are best reproduced by T(r) ∝r−1. This power law is consistent with CO line radiation being the dominant coolant in the CSE. Differences between this and other results may be the result of a previous lack of high-resolution observations, the use of older CO collisional rates, or reduced mass-loss rate. Although an assumed source distance of 150 pc gives the best fit to the data, we cannot rule out the possibility of a larger source distance (e.g. 300 pc).
ISSN:0035-8711
1365-2966
DOI:10.1093/mnras/286.4.1003