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Spinning-Down of Moving Magnetars in the Propeller Regime

O. D. Toropina·M. M. Romanova·R. V. Lovelace
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Abstract

We use axisymmetric magnetohydrodynamic simulations to investigate the spinning-down of magnetars rotating in the propeller regime and moving supersonically through the interstellar medium. The simulations indicate that magnetars spin-down rapidly due to this interaction, faster than for the case of a non-moving star. From many simulation runs we have derived an approximate scaling laws for the angular momentum loss rate, \dot{L} \propto \~η_m^{0.3}μ^{0.6}ρ^{0.8}{\cal M}^{-0.4} Ω_*^{1.5}, where ρis the density of the interstellar medium, \cal M is Mach number, μis the star's magnetic moment, Ω_* is its angular velocity, and η_m is magnetic diffusivity. A magnetar with a surface magnetic field of 10^{13} - 10^{15} G is found to spin-down to a period P > 10^5-10^6 s in \sim 10^4 - 10^5 years. There is however uncertainty about the value of the magnetic diffusivity so that the time-scale may be longer. We discuss this model in respect of Soft Gamma Repeaters (SGRs) and the isolated neutron star candidate RXJ1856.5-3754.

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O. D. Toropina, M. M. Romanova, R. V. Lovelace. 2006-06-12. Spinning-Down of Moving Magnetars in the Propeller Regime. https://doi.org/10.1111/j.1365-2966.2006.10667.x

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