Observational evidence of radial mode resonances and of nonspherical symmetry in some variable stars of δ Scuti and related types

  • W. S. Fitch
1. δ Scuti Stars
Part of the Lecture Notes in Physics book series (LNP, volume 125)


(1) For 29 (and possibly 30) multimode radial variables in the Cepheid instability strip I suggest that necessary and sufficient conditions for the existence of their multimode excitation may be that the excited periods be close to a direct resonance with each other and that their excitation growth rates be relatively small. (2) Discussion of the observational evidence on nonradial modes observed in δ Scuti and B Cephei stars suggests that radial mode excitation is always dominant when nonspherical perturbations are small or variable and that nonradial modes only appear when figure perturbations are significant, so that one seldom (or perhaps never) observes in these stars the first order m-splitting discussed by Ledoux for the case of slow rotation.


Nonlinear Coupling Mode Excitation Radial Mode Period Ratio Double Mode 
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Copyright information

© Springer-Verlag 1980

Authors and Affiliations

  • W. S. Fitch
    • 1
  1. 1.Steward ObservatoryUniversity of ArizonaTucsonArizona

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