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Spectral evolution and the onset of the X-ray GRB afterglow

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journal contribution
posted on 2012-10-24, 09:07 authored by P. A. Evans, J. P. Osborne, R. Willingale, P. T. O'Brien
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.

History

Citation

AIP Conference Proceedings, Volume 1358, Issue 1., GAMMA RAY BURSTS 2010, (2011), 117

Published in

AIP Conference Proceedings

Publisher

American Institute of Physics (AIP)

issn

0094-243X

isbn

978-0-7354-0916-3

Available date

2012-10-24

Publisher version

http://aip.scitation.org/doi/abs/10.1063/1.3621751

Language

en

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