Regular and Chaotic Pulsations of Convective Cepheid Envelopes

Abstract

Linear and nonlinear pulsational properties of convective stellar envelopes relevant for Population II Cepheids are surveyed. All models show the same trend to pass from regular to irregular behavior when a control parameter, the effective temperature, is changed. It is shown that the bifurcations to chaotic behavior persist when convection is taken into account. The transition to irregular pulsation follows well known, systematic routes to chaos, just as in the radiative case. Interestingly the inclusion of time dependent convection shifts the onset of chaos closer to the observed values of luminosity and effective temperature and thus period.