r-modes in accreting neutron stars with magnetoviscous boundary layers

Kinney, J. B., Mendell, G. (January 2003) r-modes in accreting neutron stars with magnetoviscous boundary layers. Physical Review D, 67 (2). ISSN 0556-2821

URL: http://journals.aps.org/prd/abstract/10.1103/PhysR...
DOI: 10.1103/PhysRevD.67.024032


We explore the dynamics of the r-modes in accreting neutron stars in two ways. First, we explore how dissipation in the magnetoviscous boundary layer (MVBL) at the crust-core interface governs the damping of r-mode perturbations in the fluid interior. Two models are considered: one assuming an ordinary-fluid interior, the other taking the core to consist of superfluid neutrons, type II superconducting protons, and normal electrons. We show, within our approximations, that no solution to the magnetohydrodynamic equations exists in the superfluid model when both the neutron and proton vortices are pinned. However, if just one species of vortex is pinned, we can find solutions. When the neutron vortices are pinned and the proton vortices are unpinned there is much more dissipation than in the ordinary-fluid model, unless the pinning is weak. When the proton vortices are pinned and the neutron vortices are unpinned the dissipation is comparable or slightly less than that for the ordinary-fluid model, even when the pinning is strong. We also find in the superfluid model that relatively weak radial magnetic fields ∼109G(108K/T)2 greatly affect the MVBL, though the effects of mutual friction tend to counteract the magnetic effects. Second, we evolve our two models in time, accounting for accretion, and explore how the magnetic field strength, the r-mode saturation amplitude, and the accretion rate affect the cyclic evolution of these stars. If the r-modes control the spin cycles of accreting neutron stars we find that magnetic fields can affect the clustering of the spin frequencies of low mass x-ray binaries and the fraction of these that are currently emitting gravitational waves.

Item Type: Paper
Subjects: physics
CSHL Authors:
Communities: CSHL labs > Kinney lab
Depositing User: Matt Covey
Date: 15 January 2003
Date Deposited: 30 Apr 2015 18:35
Last Modified: 30 Apr 2015 18:35
URI: http://repository.cshl.edu/id/eprint/31370

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