TURBULENT CONVECTIVE CEPHEID MODELS - LINEAR PROPERTIES

A one-dimensional turbulent convection model in the form of a time-dep endent diffusion equation for the turbulent energy is incorporated int o our numerical pulsation code. The effect of turbulent convection on the structural rearrangement of the static equilibrium star is taken i nto account, and the linear eigenvalues (periods and growth-rates) for the complete turbulent convective nonadiabatic pulsations of the equi librium models are calculated. The linearized code allows us to perfor m efficiently a systematic survey of the stability of Cepheid models f or a wide range of astrophysical parameters (L,M,T-eff) and the turbul ent 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 ca libration 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 para meters that determine the mixing length, and strengths of the eddy vis cosity and of the convective flux. The remaining parameters can be use d for fine-tuning agreement with observations.