Photometric nonadiabatic observables in rotating Cephei models

The photometric diagnostic diagrams, i.e. the amplitude ratio . phase difference dependences in different passbands, are most popular tools for mode identification in various pulsating stars. Following pioneering works (Balona & Stobie 1979, Stamford & Watson 1981) these tools have been applied mainly to Cep and Sct variables. Up to now the amplitudes and phases (photometric nonadiabatic observables) were calculated in the framework of linear nonadiabatic theory ignoring effects of rotation. With this approximation the modes with different degrees are located in well separated regions of the diagnostic diagrams. However this nice picture is spoiled by rotation, that couples modes of close frequencies and 's differing by 2. Using the third order perturbation theory (Soufi, Goupil, Dziembowski 1998) we calculated the photometric observables in and Strömgren passbands for a sequence of Cephei models. It turned out that a coupled mode is not located in the diagnostic diagrams between two (three) pure modes, as one can naively expect, but may get the position, where no pure mode ever appears. Mode position varies strongly with the inclination angle. Detailed forms of mode migration with aspect are illustrated in few representative examples.

 
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