8th HEAD Meeting, 8-11 September, 2004
Session 22 Gamma-ray Bursts
Oral, Friday, September 10, 2004, 9:00-10:30am

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[22.06] X-ray lines in Gamma Ray Burst Afterglows

J. N. Reeves (NASA-GSFC/USRA), D. Watson (University of Copenhagen), J. Osborne, P. T. O'Brien (University of Leicester)

The evidence from XMM-Newton observations for X-ray emission lines in the spectra of GRB afterglows will be discussed. At least three of the XMM-Newton afterglows show evidence for X-ray emission lines; in GRB 011211, GRB 030227 and most recently in GRB 040106. GRB 011211 was the first burst where putative soft X-ray lines from Si, S, Ar and Ca were identified, the 0.1c blue-shift of the lines compared to the known redshift of the host implied that the emitting material was most likely the ejecta from a supernova. Here, we will address the statistical concerns raised over all the XMM-Newton line detections to date, from the results of our extensive Monte Carlo simulations. We also show that none of the line emission features are due to calibration.

New results on a rapid follow-up of the recent Integral burst, GRB 040106, will also be presented. GRB 040106 is the brightest X-ray afterglow observed to date by XMM-Newton and the first afterglow where high resolution spectroscopy with the RGS (Reflection Grating Spectrometer) has been possible. Emission lines below 1 keV were observed simultaneously in both the EPIC and RGS minstruments, confirming their detection. The lines appear resolved, with a velocity width of 7000 km/s consistent with emission from a rapidly expanding shell of gas originating from a supernova/hypernova explosion.

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Bulletin of the American Astronomical Society, 36 #3
© 2004. The American Astronomical Soceity.