Volume 454, Number 2, August I 2006
APEX Special Booklet
|Page(s)||L103 - L106|
|Published online||11 July 2006|
Letter to the Editor
Mass-loss properties of S-stars on the AGB
Stockholm Observatory, AlbaNova University Center, 106 91 Stockholm, Sweden e-mail: email@example.com
2 Onsala Space Observatory, 439 92 Onsala, Sweden
3 European Southern Observatory, Casilla 19001, Santiago 19, Chile
Accepted: 12 May 2006
We have used a detailed non-LTE radiative transfer code to model new APEX CO(J = 3 2) data, and existing CO radio line data, on a sample of 40 AGB S-stars. The derived mass-loss-rate distribution has a median value of 2 10 yr-1, and resembles values obtained for similar samples of M-stars and carbon stars. Possibly, there is a scarcity of high-mass-loss-rate (≥10 yr-1) S-stars. The distribution of envelope gas expansion velocities is similar to that of the M-stars, the median is 7.5 km s-1, while the carbon stars, in general, have higher gas expansion velocities. The mass-loss rate correlates well with the gas expansion velocity, in accordance with results for M-stars and carbon stars.
Key words: stars: AGB and post-AGB / stars: circumstellar matter / stars: late-type / stars: mass-loss
© ESO, 2006
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