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Title: An external shock origin of GRB 141028A

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. In conclusion, 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 anmore » external shock origin of their prompt phase.« less
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  1. Oskar Klein Centre for Cosmoparticle Physics, AlbaNova, Stockholm (Sweden); KTH Royal Inst. of Technology, Stockholm (Sweden). AlbaNova Univ. Center, Dept. of Physics
  2. Stanford Univ., CA (United States). Kavli Inst. for Particle Astrophysics and Cosmology, W. W. Hansen Experimental Physics Lab., Dept. of Physics; SLAC National Accelerator Lab., Menlo Park, CA (United States)
  3. Univ. College Cork, Cork (Ireland). Dept. of Physics
  4. NASA Goddard Space Flight Center (GSFC), Greenbelt, MD (United States)
Publication Date:
Grant/Contract Number:
AC02-76SF00515; GO4-15073Z; NAS8-03060
Accepted Manuscript
Journal Name:
The Astrophysical Journal (Online)
Additional Journal Information:
Journal Name: The Astrophysical Journal (Online); Journal Volume: 822; Journal Issue: 2; Journal ID: ISSN 1538-4357
Institute of Physics (IOP)
Research Org:
SLAC National Accelerator Lab., Menlo Park, CA (United States); KTH Royal Inst. of Technology, Stockholm (Sweden)
Sponsoring Org:
USDOE; National Aeronautic and Space Administration (NASA); Alternative Energies and Atomic Energy Commission (CEA) (France)
Contributing Orgs:
Fermi LAT Collaboration
Country of Publication:
United States
79 ASTRONOMY AND ASTROPHYSICS; gamma-ray burst; radiation mechanisms non-thermal; radiation mechanisms thermal
OSTI Identifier: