Electrodynamics of Magnetars: Implications for the Persistent X-ray Emission and Spindown of the Soft Gamma Repeaters and Anomalous X-ray Pulsars
Reads0
Chats0
TLDR
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
More filters
Journal ArticleDOI
X-Ray Observations of High-B Radio Pulsars
S. A. Olausen,Weiwei Zhu,Julia Vogel,V. M. Kaspi,Andrew Lyne,Cristobal M. Espinoza,Ben Stappers,Richard N. Manchester,Maura McLaughlin +8 more
TL;DR: In this paper, a deep XMM-Newton observation of PSR J1734-3333 was performed to detect no X-ray pulsations from the source, setting a 1σ upper limit on the pulsed fraction of 60% in the 0.5-3-keV band, supporting the hypothesis that the magnetic field affects the observed thermal properties of pulsars.
Journal ArticleDOI
Magnetars: Time evolution, superfluid properties, and the mechanism of magnetic field decay
TL;DR: In this article, the authors calculate the coupled thermal evolution and magnetic field decay in relativistic model neutron stars threaded by superstrong magnetic fields (B > 1015 G), and evaluate how such "magnetars" evolve with time and how field decay modifies the transitions to core superfluidity.
Journal ArticleDOI
On the Nature of Quasi-periodic Oscillations in the Tail of Soft Gamma Repeater Giant Flares
TL;DR: In this paper, a model for the quasi-periodic component of magnetar emission during the tail phase of giant flares is presented, which invokes modulation of the particle number density in the magnetosphere.
Journal ArticleDOI
On the trigger mechanisms for SGR giant flares
Ramandeep Gill,Jeremy S. Heyl +1 more
TL;DR: In this paper, the authors examined two trigger mechanisms, one internal and the other external to the neutron star, that give rise to the intense soft gamma-ray repeater (SGR) giant flares.
Journal ArticleDOI
Chandra observations of the high-magnetic-field radio pulsar j1718–3718
Weiwei Zhu,Victoria M. Kaspi,Victoria M. Kaspi,Maura McLaughlin,Maura McLaughlin,George G. Pavlov,Chi-Yung Ng,Richard N. Manchester,Bryan Gaensler,Peter M. Woods +9 more
TL;DR: In this article, Chandra observations of the high-magnetic-field pulsar J1718-3718 (B = 7.4 × 1013 G) were used to study the relationship between magnetars and radio pulsars.
References
More filters
Journal ArticleDOI
Formation of very strongly magnetized neutron stars - Implications for gamma-ray bursts
TL;DR: In this article, it is argued that a convective dynamo can also generate a very strong dipole field after the merger of a neutron star binary, but only if the merged star survives for as long as about 10-100 ms.
Journal ArticleDOI
Theory of pulsars: polar gaps, sparks, and coherent microwave radiation
Ruderman,P.G. Sutherland +1 more
Journal ArticleDOI
The soft gamma repeaters as very strongly magnetized neutron stars - I. Radiative mechanism for outbursts
Journal ArticleDOI
The Soft Gamma Repeaters as Very Strongly Magnetized Neutron Stars. II. Quiescent Neutrino, X-Ray, and Alfvén Wave Emission
TL;DR: In this article, the decay rate of the core field is a very strong function of temperature and therefore of the magnetic flux density, which is not present in the decay of the weaker fields associated with ordinary radio pulsars.
Journal ArticleDOI
An X-ray pulsar with a superstrong magnetic field in the soft γ-ray repeater SGR1806 − 20
Chryssa Kouveliotou,Chryssa Kouveliotou,S. Dieters,S. Dieters,Tod E. Strohmayer,Tod E. Strohmayer,J. van Paradijs,Gerald J. Fishman,Charles A. Meegan,Kevin Hurley,Jefferson M. Kommers,Ian Smith,Dale A. Frail,Toshio Murakami +13 more
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.