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Astron. Astrophys. 358, 575-582 (2000)
The contribution of the micro-turbulent velocity on the modelling of chromospheric lines in late type dwarfs *
D. Jevremovi
1,2,
J.G. Doyle 1 and
C.I. Short 3
1 Armagh Observatory, College Hill, Armagh BT61 9DG, N. Ireland (djc,jgd@star.arm.ac.uk)
2 Belgrade Observatory, Volgina 7, 11160 Belgrade 74, Yugoslavia
3 Department of Physics and Astronomy, University of Georgia, Athens, GA 30602-2451, USA
Received 29 October 1999 / Accepted 11 April 2000
Abstract
We discuss the influence of the non-thermal velocity
(micro-turbulence) on the formation of chromospheric lines in the
atmospheres of late type dwarfs. A review of previous work shows a
variety of different approaches to the problem leading to different
atmospheric structures and consequently different computed line
profiles. In that light, we re-examine the formation of the Hydrogen
Balmer lines and Na I D lines using twelve different
distributions of the micro-turbulent velocity throughout the
atmosphere. Our results show a wide range of possible line shapes.
Using the analogy with the solar case and the latest results of the
non-thermal component widths as derived from instruments on-board SOHO
we model H![[FORMULA]](img1.gif)
and the Na I
D lines in an active dMe star Gl 616.2.
Key words: line:
formation 
line: profiles
turbulence
stars: activity
stars:
chromospheres
stars: late-type
* Based in part on observations made at Observatoire de Haute Provence (CNRS), France and SOHO
Send offprint requests to: D. Jevremovi
Contents
- 1. Introduction
- 2. Construction of models and details of the calculations
- 3. Results
- 4. Comparison with the observations - the case of CR Dra
- 5. Conclusions
- Acknowledgements
- References
© European Southern Observatory (ESO) 2000
Online publication: June 8, 2000
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