Rapidly oscillating AP stars.
Abstract
The discovery of rapid light variations with periods in the range of 6-12 min in five cool magnetic Ap stars is reported. It is noted that all of the data for these stars are consistent with the hypothesis that they are pulsating in l = 1 or l = 2 nonradial p-modes of very high overtone, k, with their pulsation axes and magnetic axes aligned. By extension of the oblique rotator model, the oblique pulsator model is suggested, this model predicts from the frequencies and amplitudes of pulsation the values of i (the inclination of the rotation axis to the line-of-sight), beta (the inclination of the magnetic axis to the rotation axis), and Prot (the rotation period of the star). A polarity-reversing magnetic field is predicted for the star HD 83368. A discussion is included of the possibility that these stars are Delta Scuti stars or, alternatively, that pulsation in many high overtone modes is common among stars, but that only some stars pulsate in just a few modes, making it possible to detect their integrated variations. It is suggested that either the magnetic field structure or density discontinuities in the atmospheres of these stars create a trap for just these few modes. The possible temperature range of the rapidly oscillating Ap stars is considered, with attention given to 21 Com in this context.
- Publication:
-
Monthly Notices of the Royal Astronomical Society
- Pub Date:
- September 1982
- DOI:
- 10.1093/mnras/200.3.807
- Bibcode:
- 1982MNRAS.200..807K
- Keywords:
-
- A Stars;
- Magnetic Field Configurations;
- Magnetic Stars;
- Peculiar Stars;
- Stellar Models;
- Stellar Oscillations;
- Atmospheric Density;
- Light Curve;
- Spectral Energy Distribution;
- Stellar Atmospheres;
- Stellar Magnetic Fields;
- Stellar Temperature;
- Variable Stars;
- Astrophysics