Theory for the Distorted Dipole Modes of the Rapidly Oscillating AP Stars: A Refinement of the Oblique Pulsator Model
Abstract
Recently, one of the rapidly oscillating Ap stars, HR 3831, has been found to have an equally split frequency septuplet, though its oscillation seems to be essentially an axisymmetric dipole mode with respect to the magnetic axis, which is oblique to the rotation axis (Kurtz 1992, Monthly Notices Roy. Astron. Soc., 259, 701; Kurtz et al. 1993, Monthly Notices Roy. Astron. Soc., 260, 343). In order to explain this fine structure, we consider the magnetic stars by taking account of the perturbations due to the magnetic fields and the rotation. We show that the effect of the magnetic field on the axisymmetric dipole modes distorts the dipole oscillation pattern to have axisymmetric octupole components, so that the frequency pattern becomes a septuplet rather than a triplet, and that the additional effect of the rotation causes the frequency pattern to be asymmetric. The formula allow us to obtain information concerning the magnetic fields, rotation, and geometrical configuration of the star from the oscillation data.
- Publication:
-
Publications of the Astronomical Society of Japan
- Pub Date:
- August 1993
- Bibcode:
- 1993PASJ...45..617S
- Keywords:
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- A Stars;
- Magnetic Stars;
- Peculiar Stars;
- Stellar Magnetic Fields;
- Stellar Oscillations;
- Stellar Rotation;
- Eigenvalues;
- Eigenvectors;
- Magnetic Dipoles;
- Perturbation Theory;
- Seismology;
- Stellar Structure;
- Astrophysics;
- ASTEROSEISMOLOGY;
- STARS: MAGNETIC;
- STARS: PECULIAR A;
- STARS: PULSATION;
- STARS: ROTATION