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Sulphur-bearing mol...
Sulphur-bearing molecules in AGB stars : II. Abundances and distributions of CS and SiS
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- Danilovich, T. (author)
- Katholieke Univ Leuven, Dept Phys & Astron, Inst Astron, Celestijnenlaan 200D, B-3001 Leuven, Belgium;Fund Sci Res FWO, Flanders, Belgium
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- Ramstedt, Sofia (author)
- Uppsala universitet,Teoretisk astrofysik
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- Gobrecht, D. (author)
- Katholieke Univ Leuven, Dept Phys & Astron, Inst Astron, Celestijnenlaan 200D, B-3001 Leuven, Belgium
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- Decin, L. (author)
- Katholieke Univ Leuven, Dept Phys & Astron, Inst Astron, Celestijnenlaan 200D, B-3001 Leuven, Belgium
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- De Beck, E. (author)
- Chalmers Univ Technol, Onsala Space Observ, Dept Space Earth & Environm, S-43992 Onsala, Sweden
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- Olofsson, H. (author)
- Chalmers Univ Technol, Onsala Space Observ, Dept Space Earth & Environm, S-43992 Onsala, Sweden
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(creator_code:org_t)
- 2018-10-01
- 2018
- English.
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In: Astronomy and Astrophysics. - : EDP SCIENCES S A. - 0004-6361 .- 1432-0746. ; 617
- Related links:
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https://www.aanda.or...
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https://urn.kb.se/re...
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https://doi.org/10.1...
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Abstract
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- Context: Sulphur has long been known to form different molecules depending on the chemical composition of its environment. More recently, the sulphur-bearing molecules SO and H2S have been shown to behave differently in oxygen-rich asymptotic giant branch (AGB) circumstellar envelopes of different densities.Aims: By surveying a diverse sample of AGB stars for CS and SiS emission, we aim to determine in which environments these sulphur bearing molecules most readily occur. We include sources with a range of mass-loss rates and carbon-rich, oxygen-rich, and mixed S-type chemistries. Where these molecules are detected, we aim to determine their CS and SiS abundances.Methods: We surveyed 20 AGB stars of different chemical types using the APEX telescope, and combined this with an IRAM 30 m and APEX survey of CS and SiS emission towards over 30 S-type stars. For those stars with detections, we performed radiative transfer modelling to determine abundances and abundance distributions.Results: We detect CS towards all the surveyed carbon stars, some S-type stars, and the highest mass-loss rate oxygen-rich stars, (M > 5 x 10(-6) M-circle dot yr(-1)). SiS is detected towards the highest mass-loss rate sources of all chemical types (M >= similar to 8 x 10(-7) M-circle dot yr(-1)). We find CS peak fractional abundances ranging from similar to 4 x 10(-7) to similar to 2 x 10(-5) for the carbon stars, from similar to 3 x 10(-8) to similar to 1 x 10(-7) for the oxygen-rich stars, and from similar to 1 x 10(-7) to similar to 8 x 10(-6) for the S-type stars. We find SiS peak fractional abundances ranging from similar to 9 x 10(-6) to similar to 2 x 10(-5) for the carbon stars, from similar to 5 x 10(-7) to similar to 2 x 10(-6) for the oxygen-rich stars, and from similar to 2 x 10(-7) to similar to 2 x 10(-6) for the S-type stars.Conclusions: Overall, we find that wind density plays an important role in determining the chemical composition of AGB circumstellar envelopes. It is seen that for oxygen-rich AGB stars both CS and SiS are detected only in the highest density circumstellar envelopes and their abundances are generally lower than for carbon-rich AGB stars by around an order of magnitude. For carbon-rich and S-type stars SiS was also only detected in the highest density circumstellar envelopes, while CS was detected consistently in all surveyed carbon stars and sporadically among the S-type stars.
Subject headings
- NATURVETENSKAP -- Fysik -- Astronomi, astrofysik och kosmologi (hsv//swe)
- NATURAL SCIENCES -- Physical Sciences -- Astronomy, Astrophysics and Cosmology (hsv//eng)
Keyword
- stars: AGB and post-AGB
- circumstellar matter
- stars: mass-loss
- stars: evolution
Publication and Content Type
- ref (subject category)
- art (subject category)
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