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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Detection of spectral evolution in the bursts emitted during the 2008-2009 active episode of SGR J1550 - 5418
Andreas von Kienlin,David Gruber,Chryssa Kouveliotou,Jonathan Granot,Matthew G. Baring,Ersin Gogus,Daniela Huppenkothen,Yuki Kaneko,Lin Lin,Anna L. Watts,P. Narayana Bhat,Sylvain Guiriec,Sylvain Guiriec,Alexander J. van der Horst,Alexander J. van der Horst,Elisabetta Bissaldi,Jochen Greiner,Charles A. Meegan,William S. Paciesas,Robert D. Preece,Arne Rau +20 more
TL;DR: In this paper, the authors analyzed the Fermi Gamma-ray Burst Monitor (GBM) data for the first and last active bursts of the SGRJ1550 -5418 (1E 1547.0 - 5408, AXJ15 5052 - 5418, PSR J1550-5418) and found that their temporal characteristics are very similar to the ones of other SGR bursts, as well the ones reported for the bursts of main episode (average burst durations \sim 170 ms).
Journal ArticleDOI
A systematic study of soft X-ray pulse profiles of magnetars in quiescence
TL;DR: In this paper, the authors performed a systematic Fourier analysis of soft X-ray pulse profiles of magnetars and found that most magnetars have a single peaked profile and hence have low amplitudes of the second Fourier harmonics (A2).
Journal ArticleDOI
Anomalous X-ray pulsars: long-term monitoring and soft-gamma repeater like X-ray bursts
TL;DR: In this article, the Rossi X-ray Timing Explorer (RXTE) was used to monitor anomalous x-ray pulsars (AXPs) using phase-coherent timing, and the authors found a wide variety of behaviors among the sources, ranging from high stability (in 1E 2259.1+586 in quiescence and 4U 0142+61), to instabilities so severe that phase coherent timing is not possible (1E 1048.1-5937).
Journal ArticleDOI
Coherent Emission in Pulsars, Magnetars, and Fast Radio Bursts: Reconnection-driven Free Electron Laser
TL;DR: In this paper, a model of the generation of coherent radio emission in the Crab pulsar, magnetars and Fast Radio Bursts (FRBs) was developed, where emission is produced by a reconnection-generated beam of particles via a variant of Free Electron Laser (FEL) mechanism, operating in a weakly-turbulent, guide-field dominated plasma.
Journal ArticleDOI
Relaxation of the chiral imbalance and the generation of magnetic fields in magnetars
Maxim Dvornikov,Maxim Dvornikov +1 more
TL;DR: In this paper, a model for the generation of magnetic fields in a neutron star, based on the magnetic field instability caused by the electroweak interaction between electrons and nucleons, is developed.
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TL;DR: In this paper, the authors reported the discovery of pulsations in the persistent X-ray flux of SGR1806-20, with a period of 7.47 s and a spindown rate of 2.6 x 10(exp -3) s/yr.