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Astron. Astrophys. 339, 525-530 (1998)
On the origin of shock waves in the ![[FORMULA]](../../../entities/lbeta.gif)
Cephei star BW Vulpeculae
*
P. Mathias 1,
D. Gillet 2,
A.B. Fokin 2, 3 and
T. Cambon 1
1 Observatoire de la Côte d'Azur, Département
Fresnel, UMR 6528, BP 4229, F-06304 Nice Cedex 04, France
2 Observatoire de Haute-Provence, F-04870 St Michel
l'Observatoire, France
3 Institute for Astronomy of the Russia Academy of
Sciences, 48 Pjatnitskaja, 109017 Moscow, Russia
Received 3 July 1998 / Accepted 12 August 1998
Abstract
New high temporal and spectral resolution observations of BW Vul
are presented. The line doubling phases, occurring twice per pulsation
cycle during the velocity discontinuities, are interpreted in terms of
shock waves. The first and largest doubling is seemingly due to the
formation of a shock wave during the supersonic infalling motion of
the atmosphere. The famous observed stillstand would be only the last
phase of the ballistic motion which seems marked by a small bounce of
the atmospheric layers on the photosphere. Then, a new shock wave,
probably initiated by the iron ![[FORMULA]](img2.gif)
-mechanism, sweeps
the layers upward. There is some indications that the amplitude of the
motion of atmospheric layers changes from one pulsation cycle to
another one.
Key words: line:
profiles 
shock waves
stars: individual:
BW Vulpeculae
stars: oscillations
* Based on observations obtained at the Observatoire de Haute Provence (France)
Send offprint requests to: P. Mathias
Contents
- 1. Introduction
- 2. Observations and data reductions
- 3. Line doubling phenomena
- 4. Shock wave origins
- 5. Conclusion
- Acknowledgements
- References
© European Southern Observatory (ESO) 1998
Online publication: October 21, 1998
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