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Title: High-energy non-thermal and thermal emission from GRB 141207A detected by Fermi

A bright long gamma-ray burst GRB 141207A was observed by the Fermi Gamma-ray Space Telescope and detected by both instruments onboard. The observations show that the spectrum in the prompt phase is not well described by the canonical empirical Band function alone, and that an additional power-law component is needed. In the early phase of the prompt emission, a modified blackbody with a hard low-energy photon index (α = +0.2 to +0.4) is detected, which suggests a photospheric origin. In a finely time-resolved analysis, the spectra are also well fitted by the modified blackbody combined with a power-law function. Here we discuss the physical parameters of the photosphere such as the bulk Lorentz factor of the relativistic flow and the radius. We also discuss the physical origin of the extra power-law component observed during the prompt phase in the context of different models such as leptonic and hadronic scenarios in the internal shock regime and synchrotron emission in the external forward shock. In the afterglow phase, the temporal and spectral behaviors of the temporally extended high-energy emission and the fading X-ray emission detected by the X-Ray Telescope on-board Swift are consistent with synchrotron emission in a radiative external forward shock.
ORCiD logo [1] ; ORCiD logo [2] ; ORCiD logo [3] ; ORCiD logo [4] ; ORCiD logo [5] ; ORCiD logo [6] ;  [7] ; ORCiD logo [7]
  1. Waseda Univ., Shinjuku, Tokyo (Japan). Research Inst. for Science and Engineering; Tokyo Inst. of Technology (Japan)
  2. Univ. of Tokyo (Japan). Inst. for Cosmic Ray Research
  3. Hiroshima Univ., Higashi-Hiroshima, Hiroshima (Japan). Dept. of Physical Sciences
  4. Univ. of Alabama, Huntsville, AL (United States). Center for Space Plasma and Aeronomic Research (CSPAR)
  5. KTH Royal Inst. of Technology, Stockholm (Sweden). Dept. of Physics; Tokyo Metropolitan Univ., Hachioji, Tokyo (Japan). Dept. of Physics
  6. Istituto Nazionale di Astrofisica (INAF), Bari (Italy)
  7. Tokyo Inst. of Technology (Japan)
Publication Date:
Grant/Contract Number:
AC02-76SF00515; 24103002
Accepted Manuscript
Journal Name:
The Astrophysical Journal (Online)
Additional Journal Information:
Journal Name: The Astrophysical Journal (Online); Journal Volume: 833; Journal Issue: 2; Journal ID: ISSN 1538-4357
Institute of Physics (IOP)
Research Org:
SLAC National Accelerator Lab., Menlo Park, CA (United States)
Sponsoring Org:
USDOE; National Aeronautic and Space Administration (NASA); Centre National de la Recherche Scientifique (CNRS); Istituto Nazionale di Fisica Nucleare (INFN); Ministry of Education, Culture, Sports, Science and Technology (MEXT); Japan Aerospace Exploration Agency (JAXA); Swedish Research Council (SRC)
Contributing Orgs:
Fermi LAT Collaboration
Country of Publication:
United States
79 ASTRONOMY AND ASTROPHYSICS; acceleration of particles; gamma-ray burst: individual (GRB 141207A); radiation mechanisms: thermal
OSTI Identifier: