Please use this identifier to cite or link to this item: http://hdl.handle.net/2381/18856
 Title: GRB 050822: Detailed analysis of an XRF observed by Swift Authors: Godet, O.Page, K. L.Osborne, J.O'Brien, P. T.Beardmore, A. P.Goad, M. R.Zhang, B.Hill, J. E.Burrows, D. N.Racusin, J.Falcone, A.Morris, D. C.Ziaeepour, H. First Published: Aug-2007 Publisher: EDP Sciences for European Southern Observatory (ESO) Citation: Astronomy & Astrophysics, 2007, 471 (2), pp. 385-394 Abstract: We report on the temporal and spectral characteristics of the early X-ray emission from the GRB 050822 as observed by Swift. This burst is likely to be an XRF showing major X-ray flares in its XRT light-curve. The quality of the data allows a detailed spectral analysis of the early afterglow in the X-ray band. During the X-ray flares, a positive correlation between the count rate and the spectral hardness (i.e. the higher the count rate, the harder the spectrum) is clearly seen for the X-ray flares. This behaviour, similar to that seen for Gamma-ray pulses, indicates that the energy peak of the spectrum is in the XRT energy band and it moves towards lower energies with time. We show evidence for the possible detection of the emergence of the forward-shock emission, produced at a radius larger than 4 $\times$ 1016 cm in the case of a CBM afterglow model (a formation region clearly different from that producing the prompt emission). Finally, we show that the null detection of a jet break up to T0+4 $\times$ 106 s in the X-ray light curve of this XRF can be understood: i) if the jet seen on-axis is uniform with a large opening angle ( $\theta > 20^\circ$); or ii) if the jet is a structured Gaussian-like jet with the line-of-sight outside the bright Gaussian core. DOI Link: 10.1051/0004-6361:20077266 ISSN: 0004-6361 eISSN: 1432-0746 Links: http://hdl.handle.net/2381/18856http://www.aanda.org/articles/aa/abs/2007/32/aa7266-07/aa7266-07.html Version: Publisher Version Status: Peer-reviewed Type: Journal Article Rights: Copyright © 2007 ESO. Reproduced with permission from Astronomy & Astrophysics, © ESO. Appears in Collections: Published Articles, Dept. of Physics and Astronomy

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