Volume 566, June 2014
|Number of page(s)||13|
|Section||Interstellar and circumstellar matter|
|Published online||17 June 2014|
Dusty shells surrounding the carbon variables S Scuti and RT Capricorni⋆
Department of AstrophysicsUniversity of Vienna,
2 Koninklijke Sterrenwacht van België, Ringlaan 3, 1180 Brussels, Belgium
3 Instituut voor Sterrenkunde, KU Leuven, Celestijnenlaan, 200D, 3001 Leuven, Belgium
4 Department of Physics and Astrophysics, Vrije Universiteit Brussel, Pleinlaan 2, 1050 Brussels, Belgium
Accepted: 5 May 2014
For the Mass-loss of Evolved StarS (MESS) programme, the unprecedented spatial resolution of the PACS photometer on board the Herschel Space Observatory was employed to map the dusty environments of asymptotic giant branch (AGB) and red supergiant (RSG) stars. Among the morphologically heterogeneous sample, a small fraction of targets is enclosed by spherically symmetric detached envelopes. Based on observations in the 70 μm and 160 μm wavelength bands, we investigated the surroundings of the two carbon semiregular variables S Sct and RT Cap, which both show evidence for a history of highly variable mass-loss. S Sct exhibits a bright, spherically symmetric detached shell, 138″ in diameter and co-spatial with an already known CO structure. Moreover, weak emission is detected at the outskirts, where the morphology seems indicative of a mild shaping by interaction of the wind with the interstellar medium, which is also supported by the stellar space motion. Two shells are found around RT Cap that were not known so far in either dust emission or from molecular line observations. The inner shell with a diameter of 188″ shows an almost immaculate spherical symmetry, while the outer ~5′ structure is more irregularly shaped. MoD, a modification of the DUSTY radiative transfer code, was used to model the detached shells. Dust temperatures, shell dust masses, and mass-loss rates are derived for both targets.
Key words: stars: AGB and post-AGB / stars: carbon / stars: mass-loss / infrared: stars / stars: individual: S Sct / stars: individual: RT Cap
Appendices are available in electronic form at http://www.aanda.org
© ESO, 2014
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