The Be Star Newsletter, Volume 37 - June 2003

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Interactions between Rotation and Pulsation

R. H. D. Townsend

Department of Physics & Astronomy, University College London, Gower Street, London WC1E 6BT, UK

In this contribution, I will examine the interaction between stellar rotation and pulsation. I begin with a brief review of the non-rotating case, emphasizing the character of pulsations as azimuthally-propagating waves. I then go on to discuss how these waves are modified under the influence of the centrifugal and Coriolis forces. Through simple arguments, I outline the conditions under which each force can become significant in determining the wave dynamics. Particular attention is paid to the Coriolis force, since it is responsible for the formation of a waveguide, which confines the pulsation to a narrow band centered on the stellar equator. Using the example of a prograde sectoral pulsation mode, I explain the basic physical principles underlying this trapping.

The Coriolis force is also responsible for the existence of Rossby waves, which are not found in non-rotating stars. I demonstrate how these waves may be understood in terms of a conservation law for angular momentum, and review their most important characteristics. I then examine how rotation modifies the frequencies of pulsation, and explain how observations of such modifications can provide information regarding a star's rotation rate. To conclude, I focus on the converse of the pulsation-rotation interaction: how the transport of angular momentum by pulsation might be important in determining the evolution of a star's rotation profile.

To appear in Proc. IAUS 215, Stellar Rotation
Preprints from rhdt@star.ucl.ac.uk
Or on the web at http://www.star.ucl.ac.uk/~rhdt/publications/


Last modified: June 3, 2003

David McDavid
dam3ma@virginia.edu