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- Justtanont, Kay, 1965, et al.
(författare)
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W Hya through the Eye of Odin
- 2005
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Ingår i: Astronomy & Astrophysics. ; 439, s. 627-633
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Tidskriftsartikel (refereegranskat)
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| 4. |
- Justtanont, K., et al.
(författare)
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W Hya through the eye of Odin. Satellite observations of circumstellar submillimetre H2O line emission
- 2005
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Ingår i: Astronomy and Astrophysics. - : EDP Sciences. - 0004-6361 .- 1432-0746. ; 439, s. 627-633
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Tidskriftsartikel (refereegranskat)abstract
- We present Odin observations of the AGB star W Hya in the ground-state transition of ortho-H{2}O, 1{10}-101, at 557 GHz. The line is clearly of circumstellar origin. Radiative transfer modelling of the water lines observed by Odin and ISO results in a mass-loss rate of (2.5±0.5)×10-7 Mȯ yr-1, and a circumstellar H{2}O abundance of (2.0±1.0)×10-3. The inferred mass-loss rate is consistent with that obtained from modelling the circumstellar CO radio line emission, and also with that obtained from the dust emission modelling combined with a dynamical model for the outflow. The very high water abundance, higher than the cosmic oxygen abundance, can be explained by invoking an injection of excess water from evaporating icy bodies in the system. The required extra mass of water is quite small, on the order of 0.1 Moplus.
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- Maercker, Matthias, et al.
(författare)
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Circumstellar water vapour in M-type AGB stars: constraints from H2O(1,10-1,01) lines obtained with odin
- 2009
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Ingår i: Astronomy and Astrophysics. - : EDP Sciences. - 0004-6361 .- 1432-0746. ; 494, s. 243-252
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Tidskriftsartikel (refereegranskat)abstract
- Context. A detailed radiative transfer code has been previously used to model circumstellar ortho-H2O line emission towards six M-type asymptotic giant branch stars using Infrared Space Observatory Long Wavelength Spectrometer data. Collisional and radiative excitation, including the v(2) = 1 state, was considered. Aims. Spectrally resolved circumstellar H2O(1(10)-1(01)) lines have been obtained towards three M-type AGB stars using the Odin satellite. This provides additional strong constraints on the properties of circumstellar H2O, in particular on the chemistry in the stellar atmosphere, and the photodissociation in the outer envelope. Methods. Infrared Space Observatory and Odin satellite H2O line data are used as constraints for radiative transfer models. Special consideration is taken to the spectrally resolved Odin line profiles, and the effect of excitation to the first excited vibrational states of the stretching modes (v(1) = 1 and v(3) = 1) on the derived abundances is estimated. A non-local, radiative transfer code based on the accelerated lambda iteration formalism is used. A statistical analysis is performed to determine the best-fit models. Results. The H2O abundance estimates are in agreement with previous estimates. The inclusion of the Odin data sets stronger constraints on the size of the H2O envelope. The H2O(1(10)-1(01)) line profiles require a significant reduction in expansion velocity compared to the terminal gas expansion velocity determined in models of CO radio line emission, indicating that the H2O emission lines probe a region where the wind is still being accelerated. Including the v(3) = 1 state significantly lowers the estimated abundances for the low-mass-loss-rate objects. This shows the importance of detailed modelling, in particular the details of the infrared spectrum in the range 3 to 6 mu m, to estimate accurate circumstellar H2O abundances. Conclusions. Spectrally resolved circumstellar H2O emission lines are important probes of the physics and chemistry in the inner regions of circumstellar envelopes around asymptotic giant branch stars. Predictions for H2O emission lines in the spectral range of the upcoming Herschel/HIFI mission indicate that these observations will be very important in this context.
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| 6. |
- Maercker, M., et al.
(författare)
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Detached Shells of Dust and Gas around Carbon Stars
- 2011
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Ingår i: Why Galaxies Care about AGB Stars II.
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Konferensbidrag (refereegranskat)abstract
- We present observations of dust-scattered light of the carbon stars U Ant, R Scl, and U Cam taken with the EFOSC2 camera on the ESO 3.6-m telescope and the ACS on the Hubble Space Telescope. The observations show the detached shells around these stars in unprecedented detail, revealing a distinctively clumpy structure in the HST images of R Scl, and a separation of the dust and gas in the ground-based data for U Ant. This allows us to investigate the detached shells and their origin with exceptional precision.
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| 7. |
- Maercker, Matthias, 1979, et al.
(författare)
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Modelling of Circumstellar H2O Line Emission from M-type AGB Stars
- 2007
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Ingår i: Proceedings of "Why galaxies care about AGB stars: their importance as actors and probes", eds. F. Kerschbaum, C. Charbonnel and R.F. Wing, Vienna, August 2006, ASP Conference Series. - 9781583813188 ; 378, s. 317-318
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)
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| 9. |
- Ramstedt, S., et al.
(författare)
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The Physics and Chemistry of Circumstellar Envelopes of S Stars on the AGB
- 2007
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Ingår i: Proceedings of " Why galaxies care about stars: their importance as actors and probes", eds. F. Kerschbaum, C. Charbonnel and R.F. Wing, Vienna, August 2006, ASP Conference Series. - 9781583813188 ; 378, s. 335-336
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)
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| 10. |
- Ryde, Nils, et al.
(författare)
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Probing the mass loss history of carbon stars using CO line and dust continuum emission
- 2002
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Ingår i: Astronomy and Astrophysics. ; 391, s. 577-
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Tidskriftsartikel (refereegranskat)abstract
- We have modelled radio and far-infrared rotational lines of (CO)-C-12 and (CO)-C-13 Obtained from the circumstellar envelope of the infrared-bright carbon star IRAS 15194-5115. Eleven rotational lines between J=1-0 and 21-20 and nine rotational lines betw
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