J. Michael Burgess, Damien Bégué, Felix Ryde, Nicola Omodei, Asaf Pe'Er, J. L. Racusin, A. Cucchiara

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The prompt emission of the long, smooth, and single-pulsed gamma-ray burst, GRB 141028A, is analyzed under the guise of an external shock model. First, we fit the γ-ray spectrum with a two-component photon model, namely, synchrotron+blackbody, and then fit the recovered evolution of the synchrotron νF ν peak to an analytic model derived considering the emission of a relativistic blast wave expanding into an external medium. The prediction of the model for the νF ν peak evolution matches well with the observations. We observe the blast wave transitioning into the deceleration phase. Furthermore, we assume the expansion of the blast wave to be nearly adiabatic, motivated by the low magnetic field deduced from the observations. This allows us to recover within an order of magnitude the flux density at the νF ν peak, which is remarkable considering the simplicity of the analytic model. Under this scenario we argue that the distinction between prompt and afterglow emission is superfluous as both early-time emission and late-time emission emanate from the same source. While the external shock model is clearly not a universal solution, this analysis opens the possibility that at least some fraction of GRBs can be explained with an external shock origin of their prompt phase.

Original languageEnglish
Article number63
JournalAstrophysical Journal
Issue number2
StatePublished - 10 May 2016
Externally publishedYes

Bibliographical note

Publisher Copyright:
© 2016. The American Astronomical Society. All rights reserved.


  • gamma-ray burst: individual (141028A)
  • radiation mechanisms: non-thermal
  • radiation mechanisms: thermal


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