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Astron. Astrophys. 336, 553-564 (1998)

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Turbulent convective cepheid models: linear properties

P.A. Yecko 1, Z. Kolláth 2 and J.R. Buchler 1

1 Physics Department, University of Florida, Gainesville, FL 32611, USA
2 Konkoly Observatory, Budapest, Hungary

Received 10 March 1998 / Accepted 28 April 1998

Abstract

A one-dimensional turbulent convection model in the form of a time-dependent diffusion equation for the turbulent energy is incorporated into our numerical pulsation code. The effect of turbulent convection on the structural rearrangement of the static equilibrium star is taken into account, and the linear eigenvalues (periods and growth-rates) for the complete turbulent convective nonadiabatic pulsations of the equilibrium models are calculated. The linearized code allows us to perform efficiently a systematic survey of the stability of Cepheid models for a wide range of astrophysical parameters (L,M,[FORMULA]) and the turbulent convective parameters.

A sensitivity analysis of the properties of several sequences of Galactic Cepheids is performed with the goal of using observational constraints, such as the shape and location of the fundamental and first overtone instability strips, to make a first calibration of the turbulent convective parameters. The locations of the red and blue edges of the fundamental and first overtone instability strips and the overall strip widths are largely determined by the parameters that determine the mixing length, and strengths of the eddy viscosity and of the convective flux. The remaining parameters can be used for fine-tuning agreement with observations.

Key words: stars: oscillations – stars: variables: RR Lyr – stars: variables: cepheids – turbulence – convection – instabilities

Send offprint requests to: J.R. Buchler

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© European Southern Observatory (ESO) 1998

Online publication: July 20, 1998
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