Electrodynamics of Magnetars: Implications for the Persistent X-ray Emission and Spindown of the Soft Gamma Repeaters and Anomalous X-ray Pulsars
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In this paper, the authors considered the structure of neutron star magnetospheres threaded by large-scale electrical currents and the effect of resonant Compton scattering by the charge carriers (both electrons and ions) on the emergent X-ray spectra and pulse profiles.Abstract:
(ABBREVIATED) We consider the structure of neutron star magnetospheres threaded by large-scale electrical currents, and the effect of resonant Compton scattering by the charge carriers (both electrons and ions) on the emergent X-ray spectra and pulse profiles. In the magnetar model for the SGRs and AXPs, these currents are maintained by magnetic stresses acting deep inside the star. We construct self-similar, force-free equilibria of the current-carrying magnetosphere with a power-law dependence of magnetic field on radius, B ~ r^(-2-p), and show that a large-scale twist softens the radial dependence to p < 1. The spindown torque acting on the star is thereby increased in comparison with a vacuum dipole. We comment on the strength of the surface magnetic field in the SGR and AXP sources, and the implications of this model for the narrow measured distribution of spin periods. A magnetosphere with a strong twist, B_\phi/B_\theta = O(1) at the equator, has an optical depth ~ 1 to resonant cyclotron scattering, independent of frequency (radius), surface magnetic field strength, or charge/mass ratio of the scattering charge. When electrons and ions supply the current, the stellar surface is also heated by the impacting charges at a rate comparable to the observed X-ray output of the SGR and AXP sources, if B_{dipole} ~ 10^{14} G. Redistribution of the emerging X-ray flux at the ion and electron cyclotron resonances will significantly modify the emerging pulse profile and, through the Doppler effect, generate a non-thermal tail to the X-ray spectrum. The sudden change in the pulse profile of SGR 1900+14 after the 27 August 1998 giant flare is related to an enhanced optical depth to electron cyclotron scattering, resulting from a sudden twist imparted to the external magnetic field.read more
Citations
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Journal ArticleDOI
Dynamics of Relativistic Reconnection
TL;DR: In this article, the steady state Sweet-Parker-type reconnection is analyzed in the relativistic regime when energy density in the inflowing region is dominated by the magnetic field.
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X-ray spectra from magnetar candidates – I. Monte Carlo simulations in the non-relativistic regime
TL;DR: In this paper, the authors present 3D Monte Carlo simulations of photon propagation in a twisted magnetosphere, based on a simplified treatment of the charge carrier velocity distribution which however accounts for the particle collective motion, in addition to the thermal one.
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A long-lived remnant neutron star after GW170817 inferred from its associated kilonova
TL;DR: In this article, a model of hybrid energy sources for the kilonova AT2017gfo associated with GW 170817 was proposed, which indicated that a long-lived remnant NS, which must own a very stiff equation of state, had been formed during the merger event.
Book
Physics of Space Plasma Activity
TL;DR: In this paper, a unified theory of steady states is presented. But it does not consider the effect of magnetic reconnection on the steady states of the plasmas and does not account for the effects of magnetohydrodynamic states.
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The magnetar XTE J1810-197: Variations in torque, radio flux density and pulse profile morphology
Fernando Camilo,Ismaël Cognard,Scott M. Ransom,Jules P. Halpern,John Reynolds,Neil Zimmerman,Eric V. Gotthelf,David J. Helfand,Paul Demorest,Gilles Theureau,Don Backer +10 more
TL;DR: In this article, the authors report on 9 months of observations of the radio-emitting anomalous X-ray pulsar XTE J1810-197 starting in 2006 May using the Nancay, Parkes, Green Bank Telescope, and VLA telescopes mainly at a frequency of 1.4 GHz.
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An X-ray pulsar with a superstrong magnetic field in the soft γ-ray repeater SGR1806 − 20
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