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Nonlinear Beat Cepheid Models

Z. Kollath·J. P. Beaulieu·J. R. Buchler·P. Yecko
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Abstract

The numerical hydrodynamic modelling of beat Cepheid behavior has been a longstanding quest in which purely radiative models have failed miserably. We find that beat pulsations occur naturally when turbulent convection is accounted for in our hydrodynamics codes. The development of a relaxation code and of a Floquet stability analysis greatly facilitates the search for and analysis of beat Cepheid models. The conditions for the occurrence of beat behavior can be understood easily and at a fundamental level with the help of amplitude equations. Here a discriminant D arises whose sign decides whether single mode or double mode pulsations can occur in a model, and this D depends only on the values of the nonlinear coupling coefficients between the fundamental and the first overtone modes. For radiative models D is always found to be negative, but with sufficiently strong turbulent convection its sign reverses.

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Z. Kollath, J. P. Beaulieu, J. R. Buchler, P. Yecko. 1998-05-19. Nonlinear Beat Cepheid Models. https://doi.org/10.1086/311484

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