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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The first outburst of the new magnetar candidate SGR 0501+4516
Nanda Rea,G. L. Israel,Roberto Turolla,Roberto Turolla,Paolo Esposito,Paolo Esposito,Sandro Mereghetti,Diego Götz,Silvia Zane,Andrea Tiengo,Kevin Hurley,Marco Feroci,M. Still,Vladimir Yershov,C. Winkler,Rosalba Perna,Federico Bernardini,Pietro Ubertini,Luigi Stella,Sergio Campana,M. van der Klis,P. M. Woods +21 more
TL;DR: In this paper, the authors studied the phase-resolved spectral evolution of the soft gamma-ray repeater SGR 0501+4516 with XMM-Newton observations for a 3-month period and found that the source flux decreased exponentially with a time-scale of t(c) = 23.8 d.
Journal ArticleDOI
Systematic study of magnetar outbursts
TL;DR: This work is supported by grants AYA2015-71042-P and SGR2014-1073 and by the Netherlands Organization for Scientific Research (NWO) Vidi award (PI: N. Rea).
Journal ArticleDOI
Resonant Cyclotron Scattering in Three Dimensions and the Quiescent Non-thermal X-ray Emission of Magnetars
TL;DR: In this paper, a Monte Carlo approach was proposed to calculate the redistribution of thermal seed photons in frequency and angle by multiple resonant scattering in the magnetosphere, including the full angular dependence of the cyclotron scattering cross section, the relativistic Doppler effect due to the motion of the charges, and allowing for an arbitrary particle velocity distribution and magnetic field geometry.
Journal ArticleDOI
The magnetar 1E 1547.0-5408: radio spectrum, polarimetry, and timing
TL;DR: In this paper, the radio emission from the anomalous X-ray pulsar 1E 1547.0-5408 (PSR J1550-5418) was investigated using the Parkes telescope and the Australia Telescope Compact Array.
Journal ArticleDOI
Spin-down Measurement of PSR J1852+0040 in Kesteven 79: Central Compact Objects as Anti-Magnetars
TL;DR: In this article, phase-connected timing of the 105 ms X-ray pulsar PSR J1852+0040 was obtained for the first measurement of the spin-down rate of a member of the class of Central Compact Objects (CCOs) in supernova remnants.
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