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Evidence for a Canonical GRB Afterglow Light Curve in the Swift/XRT DataWe present new observations of the early X-ray afterglows of the first 27 gamma-ray bursts (GRBs) detected with the Swift X-ray Telescope (XRT). The early X-ray afterglows show a canonical behavior, where the light curve broadly consists of three distinct power law segments. These power law segments are separated by two corresponding break times. On top of this canonical behavior of the early X-ray light curve, many events have superimposed X-ray flares, which are most likely caused by internal shocks due to long lasting sporadx activity of the central engine, up to several hours after the GRB. We find that the initial steep decay is consistent with it being the tail of the prompt emission: from photons that are radiated at large angles relative to our line of sight. The first break in the light curve takes place when the forward shock emission becomes dominant, with the intermediate shallow flux decay likely caused by the continuous energy injection into the external shock. When this energy injection stops, a second break is then observed in the light curve. This energy injection increases the energy of the afterglow shock by at least a factor of f greater than or approx. equal to 4, and augments the already severe requirements for the efficiency of the prompt gamma-ray emission.
Document ID
20050217170
Acquisition Source
Marshall Space Flight Center
Document Type
Preprint (Draft being sent to journal)
Authors
Nousek, J. A.
(Pennsylvania State Univ. University Park, PA, United States)
Kouveliotou, C.
(NASA Marshall Space Flight Center Huntsville, AL, United States)
Grupe, D.
(Pennsylvania State Univ. University Park, PA, United States)
Page, K.
(Leicester Univ. United Kingdom)
Granot, J.
(Stanford Univ. Stanford, CA, United States)
Ramirez-Ruiz, E.
(Institute for Advanced Study Princeton, NJ, United States)
Patel, S. K.
(NASA Marshall Space Flight Center Huntsville, AL, United States)
Burrows, D. N.
(Pennsylvania State Univ. University Park, PA, United States)
Mangano, V.
(Istituto di Fisica Spazialee Fisica Cosmica Palermo, Italy)
Barthelmy, S.
(NASA Goddard Space Flight Center Greenbelt, MD, United States)
Date Acquired
August 23, 2013
Publication Date
January 1, 2005
Subject Category
Space Radiation
Distribution Limits
Public
Copyright
Other

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