Gamma-ray bursts from Sheared Alfvén waves

Fulvio Melia, Marco Fatuzzo

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3 Scopus citations

Abstract

Sheared Alfvén waves in strongly magnetized neutron stars are efficient particle accelerators by virtue of the large electric field components Ez they generate parallel to the unperturbed magnetic field B0 = B0 ẑ. For example, with an amplitude BA0 = 1011 G (=0.1B0) and a shear wavenumber m = 0.5 (corresponding to a crustal perturbation length scale of ≈10 cm), these waves can accelerate electrons to a Lorentz factor y ∼ 104-5 within 5 km of the stellar surface, even under the influence of a Compton drag due to the thermal emission of a warm (Tpc ≲ 1 keV) polar cap. Here, we apply this physical process to a study of gamma-ray bursts, taking into account both resonant and nonresonant scattering. We also discuss several very encouraging features of the model. (1) Although the field is oscillatory, virtually all the charges are ejected from the system, resulting in very little backheating of the stellar surface. (2) The particle number density (and hence the burst energy) is accounted for naturally in terms of BA0 and m, which in principle are known from the physical manifestation of the agent causing the crustal disturbance (e.g., a thermonuclear explosion or a starquake). (3) The resulting y-ray spectrum compares very favorably with the observations. And (4) this model restricts the geometry of the emission region, in the sense that only the Compton upscattering of soft photons from a warm polar cap (as opposed, e.g., to an isotropic source) will produce the correct spectral shape.

Original languageEnglish (US)
Pages (from-to)L57-L60
JournalAstrophysical Journal
Volume383
Issue number2 PART 2
DOIs
StatePublished - Dec 20 1991

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Keywords

  • Gamma rays: bursts
  • Gamma rays: general
  • Magnetic fields
  • Particle acceleration
  • Pulsars
  • Quantum mechanics

ASJC Scopus subject areas

  • Astronomy and Astrophysics
  • Space and Planetary Science

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