Signatures of a Maxwellian component in shock-accelerated electrons in GRBs

Dimitrios Giannios, Anatoly Spitkovsky

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Recent particle-in-cell simulations suggest that a large fraction of the energy dissipated in a relativistic shock is deposited into a Maxwellian distribution of electrons that is connected to the high-energy power-law tail. Here, we explore the observational implications of such a mixed thermal-non-thermal particle distribution for the afterglow and prompt emission of gamma-ray bursts. When the Maxwellian component dominates the energy budget, the afterglow light curves show a very steep decline phase followed by a more shallow decay when the characteristic synchrotron frequency crosses the observed band. The steep decay appears in the X-rays at ∼100 s after the burst and is accompanied by a characteristic hard-soft-hard spectral evolution that has been observed in a large number of early afterglows. If internal shocks produce a similar mixed electron distribution, a bump is expected at the synchrotron peak of the νfν spectrum.

Original languageEnglish (US)
Pages (from-to)330-336
Number of pages7
JournalMonthly Notices of the Royal Astronomical Society
Issue number1
StatePublished - Nov 2009

All Science Journal Classification (ASJC) codes

  • Astronomy and Astrophysics
  • Space and Planetary Science


  • Acceleration of particles
  • Gamma-rays: Bursts
  • Radiation mechanisms: General


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