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Title: AN OBSERVED CORRELATION BETWEEN THERMAL AND NON-THERMAL EMISSION IN GAMMA-RAY BURSTS

Recent observations by the Fermi Gamma-ray Space Telescope have confirmed the existence of thermal and non-thermal components in the prompt photon spectra of some gamma-ray bursts (GRBs). Through an analysis of six bright Fermi GRBs, we have discovered a correlation between the observed photospheric and non-thermal γ-ray emission components of several GRBs using a physical model that has previously been shown to be a good fit to the Fermi data. From the spectral parameters of these fits we find that the characteristic energies, E {sub p} and kT, of these two components are correlated via the relation E {sub p}∝T {sup α} which varies from GRB to GRB. We present an interpretation in which the value of the index α indicates whether the jet is dominated by kinetic or magnetic energy. To date, this jet composition parameter has been assumed in the modeling of GRB outflows rather than derived from the data.
Authors:
;  [1] ; ;  [2] ; ;  [3] ; ; ; ;  [4] ;  [5] ;  [6] ;  [7] ;  [8] ; ; ;  [9] ; ;  [10] ;  [11] more »; « less
  1. Department of Space Science, University of Alabama in Huntsville, Huntsville, AL 35899 (United States)
  2. Department of Physics, Royal Institute of Technology (KTH), AlbaNova, SE-106 91 Stockholm (Sweden)
  3. Department of Astronomy and Astrophysics, Pennsylvania State University, University Park, PA 16802 (United States)
  4. Center for Space Plasma and Aeronomic Research (CSPAR), University of Alabama in Huntsville, Huntsville, AL 35899 (United States)
  5. Physics Department, University College Cork, Cork (Ireland)
  6. The Oskar Klein Centre for Cosmoparticle Physics, AlbaNova, SE-106 91 Stockholm (Sweden)
  7. Space Science Office, VP62, NASA/Marshall Space Flight Center, Huntsville, AL 35812 (United States)
  8. Department of Physics and Astronomy, Rice University, MS-108, P.O. Box 1892, Houston, TX 77251 (United States)
  9. University College Dublin, Belfield, Dublin 4 (Ireland)
  10. W. W. Hansen Experimental Physics Laboratory, Kavli Institute for Particle Astrophysics and Cosmology, Department of Physics and SLAC National Accelerator Laboratory, Stanford University, Stanford, CA 94305 (United States)
  11. Universities Space Research Association, Huntsville, AL 35805 (United States)
Publication Date:
OSTI Identifier:
22365923
Resource Type:
Journal Article
Resource Relation:
Journal Name: Astrophysical Journal Letters; Journal Volume: 784; Journal Issue: 2; Other Information: Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
79 ASTROPHYSICS, COSMOLOGY AND ASTRONOMY; CORRELATIONS; COSMIC GAMMA BURSTS; GAMMA RADIATION; GAMMA SPECTRA; INDEXES; JETS; PHOTON EMISSION; SPACE; TELESCOPES