Magnetar

About: Magnetar is a research topic. Over the lifetime, 2905 publications have been published within this topic receiving 106806 citations.

High Magnetic Field Rotation‐powered Pulsars

Abstract: Anomalous X‐ray pulsars and soft gamma repeaters have recently emerged as a unified class of neutron stars, identified by dramatic X‐ray and gamma‐ray outbursts and via luminous X‐ray pulsations, both thought to be powered by the decay of an enormous internal magnetic field. This “magnetar” hypothesis has raised the question of these objects’ physical relationship with conventional rotation‐powered pulsars (RPPs). The highest magnetic‐field RPPs might therefore be expected to be transition objects between the two populations. The recently reported magnetar‐like outburst of PSR J1846–0258, previously thought to be purely rotation‐powered, clearly supports this suggestion. Here we review the observational properties of the highest magnetic‐field RPPs known, and show some common characteristics that are notable among RPPs, which are plausibly related to their high fields. Using these objects, we consider the evidence for proposed “magneto‐thermal evolution” in neutron stars, and argue that while some exists, it is not yet conclusive.

New three-parameter correlation for gamma-ray bursts with a plateau phase in the afterglow

Abstract: Aims. Gamma ray bursts (GRBs) offer strong advantages because of their huge burst energies, luminosities, and high redshifts in probing the Universe. A few interesting luminosity correlations of GRBs have been used to test cosmology models. Especially, for a subsample of long GRBs with known redshifts and a plateau phase in the afterglow, a correlation between the end time of the plateau phase (in the GRB rest frame) and the corresponding X-ray luminosity has been found. Here, we add the isotropic γ-ray energy release as a third parameter to get a tighter three-parameter correlation. Methods. We reanalyzed the subsample and found that a significantly tighter correlation exists when we add the isotropic γ-ray energy release into the consideration. We used the Markov-chain Monte Carlo techniques to get the best-fit coefficients. Results. A new three-parameter correlation is found for the GRBs with an obvious plateau phase in the afterglow. The best fit correlation is found to be LX ∝ T −0.87 a E 0.88 γ,iso . Additionally, both long and intermediate duration GRBs are consistent with the same three-parameter correlation equation. Conclusions. We argue that the new three-parameter correlation is consistent with the hypothesis that the subsample of GRBs with a plateau phase in the afterglow is associated with the birth of rapidly rotating magnetars and that the plateau is due to the continuous energy-injection from the magnetar. It is suggested that the newly born millisecond magnetars associated with GRBs might provide a good standard candle in the Universe.

Global Crustal Dynamics of Magnetars in Relation to their Bright X-ray Outbursts

Abstract: This paper considers the yielding response of a neutron star crust to smooth, unbalanced Maxwell stresses imposed at the core-crust boundary, and the coupling of the dynamic crust to the external magnetic field. Stress buildup and yielding in a magnetar crust is a global phenomenon: an elastic distortion radiating from one plastically deforming zone is shown to dramatically increase the creep rate in distant zones. Runaway creep to dynamical rates is shown to be possible, being enhanced by in situ heating and suppressed by thermal conduction and shearing of an embedded magnetic field. A global and time-dependent model of elastic, plastic, magnetic, and thermal evolution is developed. Fault-like structures develop naturally, and a range of outburst timescales is observed. Transient events with time profiles similar to giant magnetar flares (millisecond rise, $\sim$ 0.1 s duration, and decaying power-law tails) result from runaway creep that starts in localized sub-km-sized patches and spreads across the crust. A one-dimensional model of stress relaxation in the vertically stratified crust shows that a modest increase in applied stress allows embedded magnetic shear to escape the star over $\sim$ 3-10 ms, dissipating greater energy if the exterior field is already sheared. Several such zones coupled to each other naturally yield a burst of duration $\sim$ 0.1 s, as is observed over a wide range of burst energies. The collective interaction of many plastic zones forces an overstability of global elastic modes of the crust, consistent with QPO activity extending over $\gtrsim$ 100 s. Giant flares probably involve sudden meltdown in localized zones, with high-frequency ($\gg$ 100 Hz) QPOs corresponding to standing Alfven waves within these zones.

Neutron Stars with Hyperons subject to Strong Magnetic Field

Abstract: Neutron stars are one of the most exotic objects in the universe and a unique laboratory to study the nuclear matter above the nuclear saturation density. In this work, we study the equation of state of the nuclear matter within a relativistic model subjected to a strong magnetic field. We then apply this EoS to study and describe some of the physical characteristics of neutron star, especially the mass-radius relation and chemical compositions. To study the influence of a the magnetic field and the hyperons in the stellar interior, we consider altogether four solutions: two different values of magnetic field to obtain a weak and a strong influence, and two configurations: a family of neutron stars formed only by protons, electrons and neutrons and a family formed by protons, electrons, neutrons, muons and hyperons. The limit and the validity of the results found are discussed with some care. In all cases the particles that constitute the neutron star are in $\beta$ equilibrium and zero total net charge. Our work indicates that the effect of a strong magnetic field has to be taken into account in the description of magnetars, mainly if we believe that there are hyperons in their interior, in which case, the influence of the magnetic field can increase the mass by more than 10%. We have also seen that although a magnetar can reach 2.48$M_{\odot}$, a natural explanation of why we do not know pulsars with masses above 2.0$M_{\odot}$ arises. We also discuss how the magnetic field affects the strangeness fraction in some standard neutron star masses and, to conclude our paper, we revisit the direct URCA process related to the cooling of the neutron stars and show how it is affected by the hyperons and the magnetic field.

NuSTAR observations of magnetar 1E 1841-045

Abstract: We report new spectral and temporal observations of the magnetar 1E 1841-045 in the Kes 73 supernova remnant obtained with the Nuclear Spectroscopic Telescope Array (NuSTAR). Combined with new Swift and archival XMM-Newton and Chandra observations, the phase-averaged spectrum is well characterized by a blackbody plus double power-law model, in agreement with previous, multi-mission X-ray results. However, we are unable to reproduce the spectral results reported using Suzaku observations. The pulsed fraction of the source is found to increase with photon energy. The measured rms pulsed fraction is ~12% and ~17% at ~20 keV and ~50 keV, respectively. We detect a new feature in the 24--35 keV band pulse profile that is uniquely double-peaked. This feature may be associated with a possible absorption or emission feature in the phase-resolved spectrum. We fit the X-ray data using the recently developed electron-positron outflow model of Beloborodov (2013) for the hard X-ray emission from magnetars. This produces a satisfactory fit allowing a constraint on the angle between the rotation and magnetic axes of the neutron star of ~20 degrees and on the angle between the rotation axis and line-of-sight of ~50 degrees. In this model, the soft X-ray component is inconsistent with a single blackbody; adding a second blackbody or a power-law component fits the data. The two-blackbody interpretation suggests a hot spot of temperature kT~0.9 keV occupying ~1% of the stellar surface.