Oscillations of rotating magnetized neutron stars with purely toroidal magnetic fields

S. K. Lander, D. I. Jones, A. Passamonti

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32 Citations (Scopus)

Abstract

We investigate the oscillation spectrum of rotating Newtonian neutron stars endowed with purely toroidal magnetic fields, using a time-evolution code to evolve linear perturbations in the Cowling approximation. The background star is generated by numerically solving the magnetohydrodynamics equilibrium equations and may be non-spherical by virtue of both rotation and magnetic effects; hence, our perturbations and background are fully consistent. Whilst the background field is purely toroidal, the perturbed field is mixed poloidal-toroidal. From Fourier analysis of the perturbations, we are able to identify a number of magnetically restored Alfvén (or a) modes. We show that in a rotating star pure inertial and a-modes are replaced by hybrid magneto-inertial modes, which reduce to a-modes in the non-rotating limit and inertial modes in the non-magnetic limit. We show that the r-mode instability is suppressed by magnetic fields in sufficiently slowly rotating stars. In addition, we determine magnetic frequency shifts in the f-mode. We discuss the astrophysical relevance of our results, in particular for magnetar oscillations.

Original languageEnglish
Pages (from-to)318-328
Number of pages11
JournalMonthly Notices of the Royal Astronomical Society
Volume405
Issue number1
DOIs
Publication statusPublished - 1 Jun 2010

Keywords

  • MHD
  • Stars: magnetic fields
  • Stars: neutron
  • Stars: oscillations
  • Stars: rotation

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