Please use this identifier to cite or link to this item: http://hdl.handle.net/2381/26241
 Title: Soft X-ray emission lines in the afterglow spectrum of GRB 011211: A detailed XMM-Newton analysis Authors: Reeves, J. N.Watson, D.Osborne, J. P.Pounds, K. A.O'Brien, P. T. First Published: 1-May-2003 Publisher: EDP Sciences for European Southern Observatory (ESO) Citation: Astronomy & Astrophysics, 2003, 403 (2), pp. 463-472 Abstract: We report on an XMM-Newton observation of the X-ray afterglow of the Gamma Ray Burst GRB 011211, originally detected by Beppo-SAX on 11th December 2001. The early afterglow spectrum obtained by XMM-Newton, observed 11 hours after the initial burst, appeared to reveal decaying H-like K $\alpha$ emission lines of Mg, Si, S, Ar and Ca, arising in enriched material with an outflow velocity of order 0.1c (Reeves et al. 2002). This was attributed to matter ejected from a massive stellar progenitor occurring shortly before the burst itself. Here, we present a detailed re-analysis of the XMM-Newton EPIC observations of GRB 011211. In particular, we show that the detection of the soft X-ray line emission appears robust, regardless of detector background, calibration, spectral binning, or the spectral model that is assumed. We demonstrate that thermal emission, from an optically thin plasma, is the most plausible model that can account for the soft X-ray emission, which appears to be the case for at least two burst afterglow spectra observed by XMM-Newton. The X-ray spectrum of GRB 011211 appears to evolve with time after the first 10 ks of the XMM-Newton observation as the Si and S emission lines are only detected during the first 10 ks of observation. The observations suggest that thermal emission is present during the early afterglow spectrum, whilst a power-law component dominates the latter stages. Finally we estimate the mass of the ejected material in GRB 011211 to be of the order 4-20 solar masses. DOI Link: 10.1051/0004-6361:20030204 ISSN: 0004-6361 Links: http://hdl.handle.net/2381/26241http://www.aanda.org/articles/aa/abs/2003/20/aah3802/aah3802.html Version: Publisher Version Status: Peer-reviewed Type: Journal Article Rights: Copyright © 2003 ESO. Reproduced with permission from Astronomy & Astrophysics, © ESO. Appears in Collections: Published Articles, Dept. of Physics and Astronomy

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