Nature, 416, 512-515 (2002) 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.
The Swift Gamma-Ray Explorer is designed to make prompt multiwavelength observations of Gamma-Ray Bursts (GRBs) and GRB afterglows. The X-ray Telescope (XRT) enables Swift to determine GRB positions ...with a few arcseconds accuracy within 100 seconds of the burst onset. The XRT utilizes a mirror set built for JET-X and an XMM/EPIC MOS CCD detector to provide a sensitive broad-band (0.2-10 keV) X-ray imager with effective area of > 120 cm^2 at 1.5 keV, field of view of 23.6 x 23.6 arcminutes, and angular resolution of 18 arcseconds (HPD). The detection sensitivity is 2x10^-14 erg cm^-2 s^-1 in 10^4 seconds. The instrument is designed to provide automated source detection and position reporting within 5 seconds of target acquisition. It can also measure the redshifts of GRBs with Fe line emission or other spectral features. The XRT operates in an auto-exposure mode, adjusting the CCD readout mode automatically to optimize the science return for each frame as the source intensity fades. The XRT will measure spectra and lightcurves of the GRB afterglow beginning about a minute after the burst and will follow each burst for days or weeks.
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.
