A non-adiabatic analysis for axisymmetric pulsations of magnetic stars

Hideyuki Saio

Research output: Contribution to journalArticle

95 Citations (Scopus)

Abstract

This paper presents the results of a non-adiabatic analysis for axisymmetric non-radial pulsations including the effect of a dipole magnetic field. Convection is assumed to be suppressed in the stellar envelope, and the diffusion approximation is used to radiative transport. As in a previous adiabatic analysis, the eigenfunctions are expanded in a series of spherical harmonics. The analysis is applied to a 1.9-M, main-sequence model (log Teff = 3.913). The presence of a magnetic field always stabilizes low-order acoustic modes. All the low-order modes of the model that are excited by the K-mechanism in the He II ionization zone in the absence of a magnetic field are found to be stabilized if the polar strength of the dipole magnetic field is larger than about 1 kG. For high-order p modes, on the other hand, distorted dipole and quadrupole modes excited by the K-mechanism in the H ionization zone remain overstable, even in the presence of a strong magnetic field. It is found, however, that all the distorted radial high-order modes are stabilized by the effect of the magnetic field. Thus, our non-adiabatic analysis suggests that distorted dipole modes and distorted quadrupole modes are most likely excited in rapidly oscillating Ap stars. The latitudinal amplitude dependence is found to be in reasonable agreement with the observationally determined one for HR 3831. Finally, the expected amplitude of magnetic perturbations at the surface is found to be very small.

Original languageEnglish
Pages (from-to)1022-1032
Number of pages11
JournalMonthly Notices of the Royal Astronomical Society
Volume360
Issue number3
DOIs
Publication statusPublished - 2005 Jul 1

Keywords

  • Stars: chemically peculiar
  • Stars: magnetic fields
  • Stars: oscillations
  • Stars: variables: other

ASJC Scopus subject areas

  • Astronomy and Astrophysics
  • Space and Planetary Science

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