Open AccessR ‐modes of a neutron star with a magnetic dipole field
Author(s) -
Lee Umin
Publication year - 2005
Publication title -
monthly notices of the royal astronomical society
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.058
H-Index - 383
eISSN - 1365-2966
pISSN - 0035-8711
DOI - 10.1111/j.1365-2966.2004.08614.x
Subject(s) - physics , neutron star , magnetic field , magnetohydrodynamics , magnetic dipole , polytropic process , dipole , magnetohydrodynamic drive , astrophysics , classical mechanics , quantum electrodynamics , computational physics , quantum mechanics
We study r ‐modes of a rotating magnetized neutron star, assuming a magnetic dipole field whose axis is aligned with the axis of rotation. We approach the problem by applying a singular perturbation theory to the oscillations of rotating stars. In this treatment, we divide the star into a thin surface magnetic layer and a non‐magnetic core. We integrate linearized ideal magnetohydrodynamic (MHD) equations in the surface magnetic layer and non‐magnetic oscillation equations in the core, and match the two integrations at the interface to obtain a complete solution. For a polytropic neutron star model of mass M = 1.4 M ⊙ and radius R = 10 6 cm, the magnetic dipole field becomes effective on the modal properties of the r ‐modes only when the field strength B S is much greater than 10 14 G. We also find that the damping effects caused by very short magnetic perturbations in the surface layer are not important for the r ‐mode instability of rapidly rotating neutron stars if the field strength B S is smaller than 10 12 G.