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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Chandra Observations of the Newly Discovered Magnetar Swift J1818.0–1607
Harsha Blumer,Samar Safi-Harb +1 more
TL;DR: In this paper, the authors report on the Chandra observations of Swift J1818.0-1607, which allowed for a high-resolution imaging and spectroscopic study of the magnetar and its environment.
Journal ArticleDOI
A phase-variable absorption feature in the X-ray spectrum of the magnetar SGR 0418+5729
Andrea Tiengo,Andrea Tiengo,Andrea Tiengo,Paolo Esposito,Sandro Mereghetti,Roberto Turolla,Roberto Turolla,L. Nobii,Fabio Gastaldello,D. Gotz,G. L. Israel,Nanda Rea,Luigi Stella,Silvia Zane,Giovanni F. Bignami,Giovanni F. Bignami +15 more
TL;DR: In this paper, an absorption feature, the properties of which strongly depend on the pulse phase, has been recently discovered in the X-ray spectrum of the soft gamma repeater SGR0418+5729 and its energy implies a magnetic field ranging from 2× 1014 G to more than 1015 G.
Journal ArticleDOI
Non-detection of pulsed radio emission from magnetar Swift J1834.9-0846: constraint on the fundamental plane of magnetar radio emission
TL;DR: In this article, it was shown that a magnetar's ability to emit radio emission may have little to do with the spin down luminosity and is related to the magnet's X-ray luminosity.
Journal ArticleDOI
Numerical simulation of oscillating magnetospheres with resistive electrodynamics
Yasufumi Kojima,Yugo E. Kato +1 more
TL;DR: In this paper, a model of the magnetosphere around an oscillating neutron star is presented, where electric charge and current induced by the stellar torsional mode are modeled using Ohm's law.
Journal ArticleDOI
On the possible wind nebula of magnetar Swift J1834.9-0846: a magnetism-powered synchrotron nebula
TL;DR: In this article, it was shown that the magnetar Swift J1834.9$-$0846 has a possible wind nebula and the required particle luminosity should be about $10,36, \,\rm erg \,s^{-1}$ to $10,38, \rm erg,s^{ −1},s −1].
References
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