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Title: Spectral evolution and the onset of the X-ray GRB afterglow
Authors: Evans, P. A.
Osborne, J. P.
Willingale, R.
O'Brien, P. T.
First Published: 19-Aug-2011
Publisher: American Institute of Physics (AIP)
Citation: GAMMA RAY BURSTS 2010, 2011, 1358, 117
Abstract: Based on light curves from the Swift Burst Analyser, we investigate whether a ‘dip’ feature commonly seen in the early‐time hardness ratios of Swift‐XRT data could arise from the juxtaposition of the decaying prompt emission and rising afterglow. We are able to model the dip as such a feature, assuming the afterglow rises as predicted by Sari and Piran [1]. Using this model we measure the initial bulk Lorentz factor of the fireball. For a sample of 23 GRBs we find a median value of Γ[subscript: 0] = 225, assuming a constant‐density circumburst medium; or Γ[subscript: 0] = 93 if we assume a wind‐like medium.
DOI Link: 10.1063/1.3621751
ISSN: 0094-243X
ISBN: 978-0-7354-0916-3
Type: Journal Article
Appears in Collections:Published Articles, Dept. of Physics and Astronomy

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