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The wind of W Hydra...
The wind of W Hydrae as seen by Herschel I. The CO envelope
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- Khouri, T. (författare)
- Anton Pannekoek Institute for Astronomy
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- de Koter, A. (författare)
- Anton Pannekoek Institute for Astronomy,Katholieke Universiteit Leuven
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- Decin, L. (författare)
- Katholieke Universiteit Leuven,Anton Pannekoek Institute for Astronomy
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- Waters, Lbfm (författare)
- Netherlands Institute for Space Research (SRON),Anton Pannekoek Institute for Astronomy
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- Lombaert, R. (författare)
- Katholieke Universiteit Leuven
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- Royer, P. (författare)
- Katholieke Universiteit Leuven
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- Swinyard, B. (författare)
- STFC Rutherford Appleton Laboratory,University College London (UCL)
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- Maercker, Matthias, 1979 (författare)
- University College London (UCL),Chalmers tekniska högskola,Chalmers University of Technology,Max Planck Gesellschaft zur Förderung der Wissenschaften e.V. (MPG),Max Planck Society for the Advancement of Science (MPG),Polish Academy of Sciences
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- Alcolea, J. (författare)
- Observatorio Astronómico Nacional (OAN),Spanish National Observatory (OAN),University College London (UCL)
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- Blommaert, Jadl (författare)
- Vrije Universiteit Brüssel (VUB),Vrije Universiteit Brussel (VUB),Katholieke Universiteit Leuven
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- Bujarrabal, V. (författare)
- Observatorio Astronómico Nacional (OAN),Spanish National Observatory (OAN),Katholieke Universiteit Leuven
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- Cernicharo, J. (författare)
- Centro de Astrobiologia (CAB)
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- Groenewegen, M. A. T. (författare)
- Royal Observatory of Belgium
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- Justtanont, Kay, 1965 (författare)
- Chalmers tekniska högskola,Chalmers University of Technology
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- Kerschbaum, F. (författare)
- Universität Wien,University of Vienna
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- Maercker, Matthias, 1979 (författare)
- Chalmers tekniska högskola,Chalmers University of Technology
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- Marston, A. P. (författare)
- European Space Astronomy Centre (ESAC),Observatorio Astronómico Nacional (OAN),Spanish National Observatory (OAN)
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- Matsuura, M. (författare)
- University College London (UCL)
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- Melnick, G. J. (författare)
- Harvard-Smithsonian Center for Astrophysics
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- Menten, K. M. (författare)
- Max Planck Gesellschaft zur Förderung der Wissenschaften e.V. (MPG),Max Planck Society for the Advancement of Science (MPG)
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- Olofsson, Hans, 1952 (författare)
- Stockholms universitet,Institutionen för astronomi,Chalmers University of Technology, Sweden,Chalmers tekniska högskola
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- Planesas, P. (författare)
- Observatorio Astronómico Nacional (OAN),Spanish National Observatory (OAN)
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- Polehampton, E. T. (författare)
- University of Lethbridge,STFC Rutherford Appleton Laboratory
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- Posch, T. (författare)
- Universität Wien,University of Vienna
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- Schmidt, M. (författare)
- Polish Academy of Sciences
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- Szczerba, R. (författare)
- Polish Academy of Sciences
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- Vandenbussche, B. (författare)
- Katholieke Universiteit Leuven
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- Yates, J. A. (författare)
- University College London (UCL)
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(creator_code:org_t)
- 2013-12-17
- 2014
- Engelska.
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Ingår i: Astronomy and Astrophysics. - : EDP Sciences. - 0004-6361 .- 1432-0746. ; 561, s. Article no. A5-
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Abstract
Ämnesord
Stäng
- Context. Asymptotic giant branch (AGB) stars lose their envelopes by means of a stellar wind whose driving mechanism is not understood well. Characterizing the composition and thermal and dynamical structure of the outflow provides constraints that are essential for understanding AGB evolution, including the rate of mass loss and isotopic ratios. Aims. We characterize the CO emission from the wind of the low mass-loss rate oxygen-rich AGB star W Hya using data obtained by the HIFI, PACS, and SPIRE instruments on board the Herschel Space Observatory and ground-based telescopes. (CO)-C-12 and (CO)-C-13 lines are used to constrain the intrinsic C-12/C-13 ratio from resolved HIFI lines. Methods. We combined a state-of-the-art molecular line emission code and a dust continuum radiative transfer code to model the CO lines and the thermal dust continuum. Results. The acceleration of the outflow up to about 5.5 km s(-1) is quite slow and can be represented by a beta-type velocity law with index beta = 5. Beyond this point, acceleration up the terminal velocity of 7 km s(-1) is faster. Using the J = 10-9, 9-8, and 6-5 transitions, we find an intrinsic C-12/C-13 ratio of 18 +/- 10 for W Hya, where the error bar is mostly due to uncertainties in the (CO)-C-12 abundance and the stellar flux around 4.6 mu m. To match the low-excitation CO lines, these molecules need to be photo-dissociated at similar to 500 stellar radii. The radial dust emission intensity profile of our stellar wind model matches PACS images at 70 mu m out to 20 '' (or 800 stellar radii). For larger radii the observed emission is substantially stronger than our model predicts, indicating that at these locations there is extra material present. Conclusions. The initial slow acceleration of the wind may imply inefficient dust formation or dust driving in the lower part of the envelope. The final injection of momentum in the wind might be the result of an increase in the opacity thanks to the late condensation of dust species. The derived intrinsic isotopologue ratio for W Hya is consistent with values set by the first dredge-up and suggestive of an initial mass of 2 M-circle dot or more. However, the uncertainty in the isotopologic ratio is large, which makes it difficult to set reliable limits on W Hya's main-sequence mass.
Ämnesord
- NATURVETENSKAP -- Fysik -- Astronomi, astrofysik och kosmologi (hsv//swe)
- NATURAL SCIENCES -- Physical Sciences -- Astronomy, Astrophysics and Cosmology (hsv//eng)
Nyckelord
- radiative-transfer
- mu-m
- molecular inventory
- Hydrae
- rich agb stars
- line: formation
- stars: individual: W
- isotope ratios
- open clusters
- circumstellar matter
- feature
- stars: AGB and post-AGB
- giant branch stars
- semiregular variables
- radiative transfer
- circumstellar water-vapor
- evolved stars
- stars: mass-loss
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- Av författaren/redakt...
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Khouri, T.
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de Koter, A.
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Decin, L.
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Waters, Lbfm
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Lombaert, R.
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Royer, P.
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visa fler...
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Swinyard, B.
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Maercker, Matthi ...
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Alcolea, J.
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Blommaert, Jadl
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Bujarrabal, V.
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Cernicharo, J.
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Groenewegen, M. ...
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Justtanont, Kay, ...
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Kerschbaum, F.
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Marston, A. P.
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Matsuura, M.
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Melnick, G. J.
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Menten, K. M.
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Olofsson, Hans, ...
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Planesas, P.
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Polehampton, E. ...
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Posch, T.
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Schmidt, M.
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Szczerba, R.
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Vandenbussche, B ...
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Yates, J. A.
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