Magnetic perturbations to the acoustic modes of roAp stars

• Type: Article in International Scientific Journal
• Date: 2000

Authors

Cunha, MS (Author) FCUP; Gough, D (Author) Other

Journal

Title: Monthly Notices of the Royal Astronomical Society

Vol. 319

Pages: 1020-1038

ISSN: 0035-8711

Publisher: Oxford University Press

Indexing

ISI Web of Knowledge - 108 Citations

Scopus - 89 Citations

Other information

Authenticus ID: P-000-Y5W

DOI: 10.1046/j.1365-8711.2000.03896.x

Abstract (EN): We study the effect of a large-scale surface magnetic field on the non-radial acoustic modes of roAp stars. Special attention is given to the use of a variational principle which is used for determining the shifts in the frequencies with relative ease, enabling us to avoid having to calculate the perturbed eigenfunctions. With knowledge of the frequency shifts we then estimate the eigenfunctions in a simpler, albeit approximate way. The results indicate frequency shifts of the order of few mu HZ, which depend on the order, degree and azimuthal order of the mode. The loss of energy through Alfven waves is also estimated from the imaginary parts of the frequency shifts. The results indicate that the loss is particularly high near specific frequencies. This might indicate the presence of a selection effect, which could make some modes more likely to be excited than others. However, our results do not explain why the modes observed appear always to be aligned with the axis of the magnetic field. Finally, the estimated perturbed eigenfunctions contain strong components of spherical harmonics that differ from those of the original unperturbed modes.

Language: English

Type (Professor's evaluation): Scientific

No. of pages: 19