Jitter Radiation as a Possible Mechanism for Gamma‐Ray Burst Afterglows: Spectra and Light Curves

Medvedev, Mikhail V.; Lazzati, Davide; Morsony, Brian J.; Workman, Jared C.

doi:10.1086/520701

Cited by 22 publications

(33 citation statements)

References 20 publications

(49 reference statements)

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“…This modifies the maximum energy of the synchrotron photons (Derishev 2007), but the radiation emitted when a particle is deflected through very small angles differs significantly from synchrotron radiation (Landau & Lifshitz 1975), and can, in principle, produce more energetic photons. This has led to the suggestion that "jitter" radiation from shock-accelerated particles is responsible for both the prompt emission (Medvedev 2006) and the afterglow (Medvedev et al 2007) from gamma-ray bursts. In this Letter, we show that the inherent weakness of the scattering produced by Weibel-driven turbulence implies that radiation losses quench first-order Fermi acceleration relatively quickly.…”

Section: Introductionmentioning

confidence: 99%

Radiative Signatures of Relativistic Shocks

Kirk

Reville

2010

ApJ

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Particle-in-cell simulations of relativistic, weakly magnetized collisionless shocks show that particles can gain energy by repeatedly crossing the shock front. This requires scattering off self-generated small length-scale magnetic fluctuations. The radiative signature of this first-order Fermi acceleration mechanism is important for models of both the prompt and afterglow emission in gamma-ray bursts and depends on the strength parameter a = λe|δB|/mc 2 of the fluctuations (λ is the length scale and |δB| is the magnitude of the fluctuations). For electrons (and positrons), acceleration saturates when the radiative losses produced by the scattering cannot be compensated by the energy gained on crossing the shock. We show that this sets an upper limit on both the electron Lorentz factor γ < 10 6 (n/1 cm −3 ) −1/6γ 1/6 and on the energy of the photons radiated during the scattering process hω max < 40 Max(a, 1)(n/1 cm −3 ) 1/6γ −1/6 eV, where n is the number density of the plasma andγ is the thermal Lorentz factor of the downstream plasma, provided a < a crit ∼ 10 6 . This rules out "jitter" radiation on self-excited fluctuations with a < 1 as a source of gamma rays, although high-energy photons might still be produced when the jitter photons are upscattered in an analog of the synchrotron self-Compton process. In fluctuations with a > 1, radiation is generated by the standard synchrotron mechanism, and the maximum photon energy rises linearly with a, until saturating at 70 MeV, when a = a crit .

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Section: Introductionmentioning

confidence: 99%

Radiative Signatures of Relativistic Shocks

Kirk

Reville

2010

ApJ

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“…The evolving current filaments produced by these instabilities lead to a densely tangled magnetic field structure which serves to ''jitter'' the electrons. In astrophysics, observations of gamma-ray bursts can be characterized by the spectra of the long-duration afterglow, which may be the result of such jitter radiation [6,7].…”

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confidence: 99%

Current Filamentation Instability in Laser Wakefield Accelerators

et al. 2011

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Experiments using an electron beam produced by laser-wakefield acceleration have shown that varying the overall beam-plasma interaction length results in current filamentation at lengths that exceed the laser depletion length in the plasma. Three-dimensional simulations show this to be a combination of hosing, beam erosion, and filamentation of the decelerated beam. This work suggests the ability to perform scaled experiments of astrophysical instabilities. Additionally, understanding the processes involved with electron beam propagation is essential to the development of wakefield accelerator applications.

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“…It's been demonstrated [17] that the jitter radiation field is anisotropic with respect to the direction of the Weibel current filaments and that its spectral and polarization characteristics are determined by microphysical plasma parameters. In particular, the peak frequency differs from the synchrotron one: Vjuter -(£B/10~3Y/ 2 v sync h, see [19]. Using the parameters of PIC simulations discussed above, we predict that radiatively efficient shocks shall have a spectral peak, E p in the MeV range, likely from tens to few hundred MeV.…”

Section: Radiation: Spectral Evolution and Spectral Correlations Obsmentioning

confidence: 89%

GRB physics with Fermi

Medvedev¹,

Meegan²,

Kouveliotou³

et al. 2009

AIP Conference Proceedings

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Radiation from GRBs in the prompt phase, flares and an afterglow is thought to be produced by accelerated electrons in magnetic fields. Such emission may be produced at collisionless shocks of baryonic outflows or at reconnection sites (at least for the prompt and flares) of the magnetically dominated (Poynting flux driven) outflows, where no shocks presumably form at all. An astonishing recent discovery is that during reconnection strong small-scale magnetic fields are produced via the Weibel instability, very much like they are produced at relativistic shocks. The relevant physics has been successfully and extensively studied with the PIC simulations in 2D and, to some extent, in 3D for the past few years. We discuss how these simulations predict the existence of MeV-range synchrotron/jitter emission in some GRBs, which can be observed with Fermi. Recent results on modeling of the spectral variability and spectral correlations of the GRB prompt emission in the Weibel-jitter paradigm applicable to both baryonic and magnetic-dominated outflows is reviewed with the emphasis on observational predictions.Comment: 6 pages; submitted to proc. of Huntsville 2008 symposium on GRB

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Jitter Radiation as a Possible Mechanism for Gamma‐Ray Burst Afterglows: Spectra and Light Curves

Cited by 22 publications

References 20 publications

Radiative Signatures of Relativistic Shocks

Radiative Signatures of Relativistic Shocks

Current Filamentation Instability in Laser Wakefield Accelerators

GRB physics with Fermi

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