The termination shock of a magnetar wind: a possible origin of gamma-ray burst X-ray afterglow emission

Mao, Zhu; Yu, Yun-Wei; Dai, Z. G.; Pi, C. M.; Zheng, Xiaoping

doi:10.1051/0004-6361/200913252

Cited by 13 publications

(25 citation statements)

References 41 publications

(37 reference statements)

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“…The comoving magnetic field strength in the emission regions is a critical parameter for the synchrotron radiation. For Region 2 (the forward-shocked medium), because the ambient medium is usually unmagnetized, the downstream magnetic field may be produced by the relativistic two-stream instability (Medvedev & Loeb 1999). This magnetic field strength is quantified by the equipartition parameter ε B, f , i.e., the ratio of magnetic energy density to the total energy density behind the forward shock.…”

Section: Discussionmentioning

confidence: 99%

“…In this scenario, a reverse shock develops and produces additional radiation signals (Dai 2004;Yu & Dai 2007;Mao et al 2010;Wang & Dai 2013;Wang et al 2015). In some cases, however, the magnetar wind may remain rather strongly magnetized at large radii.…”

Section: Modelmentioning

confidence: 99%

“…Under ideal MHD conditions, owing to the induction equation the magnetic field in the wind is dominated by its toroidal component (Fan et al 2004;Zhang & Kobayashi 2005;Mao et al 2010). Both n 4 and B 2 4 would decrease as R −2 , and as a result the magnetization parameter σ can be regarded as a constant.…”

Section: Modelmentioning

confidence: 99%

“…The connection of the two sides of the shocks can be described by the shock jump conditions (Coroniti 1990;Zhang & Kobayashi 2005;Mao et al 2010) e 2 n 2 m p c 2 = Γ 2 − 1, n 2 n 1 = 4Γ 2 + 3,…”

Section: Modelmentioning

confidence: 99%

“…The RS, arising from the interaction of the wind with the merger ejecta and external medium, depends on the magnetization of the magnetar wind (Fan et al 2004;Zhang & Kobayashi 2005;Mimica et al 2009Mimica et al , 2010Mao et al 2010). The strong magnetic fields would suppress the RS in the magnetized wind (Fan et al 2004;Zhang & Kobayashi 2005;Giannios et al 2008;Mimica et al 2009Mimica et al , 2010.…”

Section: Introductionmentioning

confidence: 99%

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Reverse shock emission driven by post-merger millisecond magnetar winds: Effects of the magnetization parameter

Liu

Wang

Dai

2016

A&A

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The study of short-duration gamma-ray bursts provides growing evidence that a good fraction of double neutron star mergers lead to the formation of stable millisecond magnetars. The launch of Poynting flux by the millisecond magnetars could leave distinct electromagnetic signatures that reveal the energy dissipation processes in the magnetar wind. In previous studies, we assume that the magnetar wind becomes completely lepton-dominated so that electrons/positrons in the magnetar wind are accelerated by a diffusive shock. However, theoretical modeling of pulsar wind nebulae shows that in many cases the magnetic field energy in the pulsar wind may be strong enough to suppress diffusive shock acceleration. In this paper, we investigate the reverse shock emission and the forward shock emission with an arbitrary magnetization parameter σ of a magnetar wind. We find that the reverse shock emission strongly depends on σ, and in particular that σ ∼ 0.3 leads to the strongest reverse shock emission. Future observations would be helpful to diagnose the composition of the magnetar wind.

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Section: Discussionmentioning

confidence: 99%

Section: Modelmentioning

confidence: 99%

Section: Modelmentioning

confidence: 99%

Section: Modelmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Reverse shock emission driven by post-merger millisecond magnetar winds: Effects of the magnetization parameter

Liu

Wang

Dai

2016

A&A

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The spectrum of electromagnetic jets from Kerr black holes and naked singularities in the Teukolsky perturbation theory

Staicova

Fiziev

2010

Astrophys Space Sci

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We give a new theoretical basis for examination of the presence of the Kerr black hole (KBH) or the Kerr naked singularity (KNS) in the central engine of different astrophysical objects around which astrophysical jets are typically formed: X-ray binary systems, gamma ray bursts (GRBs), active galactic nuclei (AGN), etc.Our method is based on the study of the exact solutions of the Teukolsky master equation for electromagnetic perturbations of the Kerr metric. By imposing original boundary conditions on the solutions so that they describe a collimated electromagnetic outflow, we obtain the spectra of possible primary jets of radiation, introduced here for the first time. The theoretical spectra of primary electromagnetic jets are calculated numerically.Our main result is a detailed description of the qualitative change of the behavior of primary electromagnetic jet frequencies under the transition from the KBH to the KNS, considered here as a bifurcation of the Kerr metric. We show that quite surprisingly the novel spectra describe linearly stable primary electromagnetic jets from both the KBH and the KNS. Numerical investigation of the dependence of these primary jet spectra on the rotation of the Kerr metric is presented and discussed.

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COASTING EXTERNAL SHOCK IN WIND MEDIUM: AN ORIGIN FOR THE X-RAY PLATEAU DECAY COMPONENT INSWIFTGAMMA-RAY BURST AFTERGLOWS

Shen

Matzner

2011

ApJ

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The plateaus observed in about one half of the early X-ray afterglows are the most puzzling feature in gamma-ray bursts (GRBs) detected by Swift. By analyzing the temporal and spectral indices of a large X-ray plateau sample, we find that 55% can be explained by external, forward shock synchrotron emission produced by a relativistic ejecta coasting in a ρ ∝ r −2 , wind-like medium; no energy injection into the shock is needed. After the ejecta collects enough medium and transitions to the adiabatic, decelerating blastwave phase, it produces the post-plateau decay. For those bursts consistent with this model, we find an upper-limit for the initial Lorentz factor of the ejecta, Γ 0 ≤ 46 (ǫ e /0.1) −0.24 (ǫ B /0.01) 0.17 ; the isotropic equivalent total ejecta energy is E iso ∼ 10 53 (ǫ e /0.1) −1.3 (ǫ B /0.01) −0.09 (t b /10 4 s) erg, where ǫ e and ǫ B are the fractions of the total energy at the shock downstream that are carried by electrons and the magnetic field, respectively, and t b is the end of the plateau. Our finding supports Wolf-Rayet stars as the progenitor stars of some GRBs. It raises intriguing questions about the origin of an intermediate-Γ 0 ejecta, which we speculate is connected to the GRB jet emergence from its host star. For the remaining 45% of the sample, the post-plateau decline is too rapid to be explained in the coasting-in-wind model, and energy injection appears to be required.

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The termination shock of a magnetar wind: a possible origin of gamma-ray burst X-ray afterglow emission

Cited by 13 publications

References 41 publications

Reverse shock emission driven by post-merger millisecond magnetar winds: Effects of the magnetization parameter

Reverse shock emission driven by post-merger millisecond magnetar winds: Effects of the magnetization parameter

The spectrum of electromagnetic jets from Kerr black holes and naked singularities in the Teukolsky perturbation theory

COASTING EXTERNAL SHOCK IN WIND MEDIUM: AN ORIGIN FOR THE X-RAY PLATEAU DECAY COMPONENT INSWIFTGAMMA-RAY BURST AFTERGLOWS

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