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The Supercritical Pile Gamma-Ray Burst Model: The GRB Afterglow Steep Decline and Plateau PhaseWe present a process that accounts for the steep decline and plateau phase of the Swift X-Ray Telescope (XRT) light curves, vexing features of gamma-ray burst (GRB) phenomenology. This process is an integral part of the "supercritical pile" GRB model, proposed a few years ago to account for the conversion of the GRB kinetic energy into radiation with a spectral peak at E(sub pk) is approx. m(sub e)C(exp 2). We compute the evolution of the relativistic blast wave (RBW) Lorentz factor Gamma to show that the radiation-reaction force due to the GRB emission can produce an abrupt, small (approx. 25%) decrease in Gamma at a radius that is smaller (depending on conditions) than the deceleration radius R(sub D). Because of this reduction, the kinematic criticality criterion of the "supercritical pile" is no longer fulfilled. Transfer of the proton energy into electrons ceases and the GRB enters abruptly the afterglow phase at a luminosity smaller by approx. m(sub p)/m(sub e) than that of the prompt emission. If the radius at which this slow-down occurs is significantly smaller than R(sub D), the RBW internal energy continues to drive the RBW expansion at a constant (new) Gamma and its X-ray luminosity remains constant until R(sub D) is reached, at which point it resumes its more conventional decay, thereby completing the "unexpected" XRT light curve phase. If this transition occurs at R is approx. equal to R(sub D), the steep decline is followed by a flux decrease instead of a "plateau," consistent with the conventional afterglow declines. Besides providing an account of these peculiarities, the model suggests that the afterglow phase may in fact begin before the RBW reaches R is approx. equal to R(sub D), thus providing novel insights into GRB phenomenology.
Document ID
20140008982
Document Type
Reprint (Version printed in journal)
Authors
Sultana, Joseph (Malta Univ. Msida, Malta)
Kazanas, D. (NASA Goddard Space Flight Center Greenbelt, MD United States)
Mastichiadis, A. (Athens Univ. Greece)
Date Acquired
July 10, 2014
Publication Date
December 1, 2013
Publication Information
Publication: The Astrophysical Journal
Volume: 779
Subject Category
Astrophysics
Report/Patent Number
GSFC-E-DAA-TN14742
Distribution Limits
Public
Copyright
Public Use Permitted.
Keywords
parameters
cosmological
burst: general

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