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Since their identification with cosmological distances, Gamma-ray bursts (GRBs) have been recognised as the most energetic phenomena in the Universe, with an isotropic burst energy as high as 10^54 ergs. However, the progenitors responsible for the bursts remain elusive, favoured models ranging from a neutron star binary merger, to the collapse of a massive star. Crucial to our understanding of the origins of GRBs is the study of the afterglow emission, where spectroscopy can reveal details of the environment of the burst. Here we report on an XMM-Newton observation of the X-ray afterglow of GRB 011211. The X-ray spectrum reveals evidence for emission lines of Magnesium, Silicon, Sulphur, Argon, Calcium, and possibly Nickel, arising in enriched material with an outflow velocity of order 0.1c. This is the first direct measurement of outflowing matter in a gamma ray burst. The observations strongly favour models where a supernova explosion from a massive stellar progenitor precedes the burst event and is responsible for the outflowing matter.
We discuss the formation of spectral features in the decelerating ejecta of gamma-ray bursts, including the possible effect of inhomogeneities. These should lead to blueshifted and broadened absorption edges and resonant features, especially from H a
In order to constrain the broad-band spectral energy distribution of the afterglow of GRB 100621A, dedicated observations were performed in the optical/near-infrared with the 7-channel Gamma-Ray Burst Optical and Near-infrared Detector (GROND) at the
We present the Hubble diagram (HD) of 66 Gamma Ray Bursts (GRBs) derived using only data from their X - ray afterglow lightcurve. To this end, we use the recently updated L_X - T_a correlation between the break time T_a and the X - ray luminosity L_X
A preponderance of evidence links long-duration, soft-spectrum gamma-ray bursts (GRBs) with the death of massive stars. The observations of the GRB-supernova (SN) connection present the most direct evidence of this physical link. We summarize 30 GRB-
(abridged) A 0.2-12 keV spectrum obtained with the XMM EPIC/pn instrument of GRB 011211 was found by Reeves et al. (2002) to contain emission lines which were interpreted to be from Mg XI, Si XIV, S XVI, Ar XVIII, and Ca XX, at a lower redshift (z_{o