| Research Abstract |
I discuss the oscillation features of the rapidly oscillating Ap stars, the Blazhko effect of the RR Lyrae stars, and β Cephei and interpret them as being a manifestation of a magnetic perturbation to the oscillation eigenfunctions of the stars.
1. The pulsation amplitude of the roAp stars varies synchronously with the magnetic variation, and the amplitude maximum phase coincides with the magnetic maximum phase. I discuss what kind of information is available and outline how it is deduced from the observational data.
2. I discuss the oscillation features of β Cephei, which is a magnetic star in which the magnetic axis seems to be oblique to the rotation axis. I interpret the observed equi-distant fine structure of the frequency spectrum as a manifestation of a magnetic perturbation of an eigenmode, which would be a radial mode in the absence of the magnetic field. Besides these frequency components, I interpret another peak in the frequency spectrum as an independent quadrupole mode. By this mode identification, I deduce the mass, the evolutionary stage, the rotational frequency, the magnetic field strength, and the geometrical configuration of β Cephei.
3. By assuming that RR Lyrae stars have fairly strong dipole magnetic fields with symmetry axis oblique to the rotation axis of the star, I show that the oscillation mode which would be a pure radial oscillation in absence of the magnetic field has a quadrupole component, whose symmetry axis coincides with the magnetic axis. The aspect angle of the quadrupole component changes due to the stellar rotation, and this apparent amplitude variation is interpreted as the Blazhko effect in RR Lyrae stars. It is shown that, in the case of off-axis magnetic field, the phase modulation is expected. I list up some theoretical predictions based on this model, which would observationally examine this hypothesis.
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