| 1. |
|
|
| 2. |
- Gustafsson, Bengt
(författare)
-
Towards a satisfactory understanding of AGB-Star Atmospheres
- 2007
-
Ingår i: Why galaxies care about AGB stars. - 9781583813188 ; , s. 60-70
-
Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- The understanding and the modelling of the atmospheres of AGB stars are discussed and found to be unsatisfactory for most purposes. A number of developments and possible actions to improve this situation are considered.
|
|
| 3. |
- Höfner, Susanne
(författare)
-
Headwind: Modelling Mass Loss of AGB Stars, Against All Odds
- 2007
-
Ingår i: Why Galaxies Care About AGB Stars: Their Importance as Actors and Probes. - 9781583813188 ; , s. p.145-155
-
Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- The intricate interplay of atmospheric shock waves and a complex, variable radiation field with non-equilibrium dust formation presents a considerable challenge to self-consistent modelling of atmospheres and winds of AGB stars. Nevertheless it is clear that realistic models predicting mass loss rates and synthetic spectra are crucial for our understanding of this important phase of stellar evolution. While a number of questions are still open, significant progress has been achieved in recent years. In particular, self-consistent models for atmospheres and winds of C-stars have reached a level of sophistication which allows direct quantitative comparison with observations. In the case of stars with C/O < 1, however, recent work points to serious problems with the dust-driven wind scenario. This contribution analyzes the basic ingredients of this scenario with analytical estimates, focusing on dust formation, non-grey effects, and differences between C-rich and O-rich environments, as well as discussing the status of detailed dynamical wind models and current trends in this field.
|
|
| 4. |
- Lederer, Michael, et al.
(författare)
-
Water Opacity in M Stars
- 2007
-
Ingår i: Why Galaxies Care About AGB Stars: Their Importance as Actors and Probes. - 9781583813188 ; , s. 127-128
-
Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- We compare the recently published BT2 water line list tep{2006MNRAS.368.1087B} with other available lists -- NASA Ames tep{partridge:4618} and SCAN tep{2001A&A...372..249J} -- and examine the impact on hydrostatic as well as dynamic models for cool M-type stars. Emerging spectra are compared to ISO-SWS observations of semiregular and Mira variables.
|
|
| 5. |
- Maercker, Matthias, 1979, et al.
(författare)
-
Modelling of Circumstellar H2O Line Emission from M-type AGB Stars
- 2007
-
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
-
Konferensbidrag (övrigt vetenskapligt/konstnärligt)
|
|
| 6. |
- Mattsson, Lars, et al.
(författare)
-
On the Connection between Mass Loss and Evolution of C-rich AGB Stars
- 2007
-
Ingår i: Why Galaxies Care About AGB Stars: Their Importance as Actors and Probes. - 9781583813188 ; , s. 239-243
-
Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- The mass-loss properties of carbon rich AGB stars are not very well constrained at present. A variety of empirical or theoretical formulae with different parameterisations are available in the literature and the agreement between them is anything but good. These simple mass-loss prescriptions are nonetheless used in many models of stellar evolution without much consideration of their applicability in various cases. We present here an on-going project aiming at a better description of the mass loss, that could be used to improve stellar evolution models -- especially the evolution during the TP-AGB phase. As a first step, we have considered the mass-loss evolution during a He-shell flash. Using stellar parameters sampled from a stellar evolutionary track, we have computed the time evolution of the atmospheric layers and wind acceleration region during a flash event with detailed frequency-dependent radiation-hydrodynamical models including dust formation. We find that existing simple mass-loss prescriptions imply mass-loss evolutions different than our model. Based on these results, we have also simulated the subsequent long-term dynamical evolution of the circumstellar envelope (CSE), including the formation of a detached shell. The second step of the project deals with the dependence of mass loss on the basic stellar parameters. At the moment we are computing a large grid of wind models for C-rich AGB stars. Preliminary results show that simple parameterisations are difficult to obtain in certain regions of the parameter space considered, due to strong non-linearities in the wind mechanism.
|
|
| 7. |
- Nowotny, Walter, et al.
(författare)
-
Tracing AGB Mass Loss by (Synthetic) High-Resolution IR Spectroscopy
- 2007
-
Ingår i: Why Galaxies Care About AGB Stars: Their Importance as Actors and Probes. - 9781583813188 ; , s. 325-326
-
Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- We report on recent advances in line profile modelling of different near-infrared (NIR) molecular absorption features based on dynamic model atmospheres for pulsating and mass-losing AGB stars (Mira variables).
|
|
| 8. |
- Ramstedt, S., et al.
(författare)
-
The Physics and Chemistry of Circumstellar Envelopes of S Stars on the AGB
- 2007
-
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
-
Konferensbidrag (övrigt vetenskapligt/konstnärligt)
|
|
| 9. |
|
|
| 10. |
- Wahlin, Rurik, et al.
(författare)
-
Carbon stars in the Bulge -- or beyond it?
- 2007
-
Ingår i: Why Galaxies Care About AGB Stars: Their Importance as Actors and Probes.. - 9781583813188 ; , s. 410-415
-
Konferensbidrag (övrigt vetenskapligt/konstnärligt)
|
|
