An external-shock origin of the  relation for gamma-ray bursts |
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| Authors: | A Panaitescu |
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| Institution: | Space Science and Applications, MS D466, Los Alamos National Laboratory, Los Alamos, NM 87545, USA |
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| Abstract: | We investigate the possibility that the  relation between the peak energy E p of the ν F ν spectrum and energy output  for long-duration gamma-ray bursts (GRBs) arises from the external shock produced by the interaction of a relativistic outflow with the ambient medium. To that aim, we take into account the dependence of all parameters which determine E p and  on the radial distribution of the ambient medium density and find that the  relation can be explained if the medium around GRBs has a universal radial stratification. For various combinations of GRB radiative process (synchrotron or inverse-Compton) and dissipation mechanism (reverse or forward shock), we find that the circumburst medium must have a particle density with a radial distribution different than the R ?2 expected for the stellar wind corresponding to a constant mass-loss rate and terminal speed. |
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| Keywords: | radiation mechanisms: non-thermal shock waves gamma-rays: bursts |
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