1994A&A...292..133F

The nonlinear pulsations of luminous 0.6M_☉ models for RV Tauri stars are studied by numerical simulation. We find typical RV Tauri behavior in a number of models within 3123≤L/L_☉≤7000 and a wide range of T_eff below 5400K, whereas hotter models exhibit pulsations in the first or second overtone. Fourier analysis of the alternating RV Tauri models reveals two strong peaks with 2:1 frequency ratio, but the origin of the low-frequency peak can hardly be explained by the period doubling hypothesis. As comparison with the linear results shows, those peaks are more likely due to the fundamental mode and the first overtone. This result supports the long-standing hypothesis of the 2:1 resonance between these modes in RV Tauri stars. The phase space reconstructions of RV Tauri models reveal chaotic behavior similar to that found in the semiregular W Virginis models. The principal physical processes in the envelopes of alternating models are discussed, and a possible explanation for the secondary variability of RVb stars is presented.