The new study, which will be reported in the April 4 issue of the journal Nature, found hot gas containing elements such as magnesium, silicon and sulfur, which are common products of a supernova, an explosion that marks the end of a massive star's life. The gas was streaming outward from a known GRB site at one-tenth the speed of light.
James Reeves of the University of Leicester, UK, led the study. Reeves explained what he figures is going on, a scenario that other researchers have described previously:
As massive star nears the end of its life, it casts huge amounts of material into space. In a grand finale, a bubble of hot gas explodes outward. Material that's left behind is thought to collapse into a black hole. The whole mess rotates, and two jets of gamma rays and other emissions are shot out in opposite directions, along the axis of rotation.
"Eventually, the hot fireball from the [supernova] burst catches up with the dense material [previously] ejected from the massive progenitor star," Reeves said. "This material is heated up and produces the X-ray emission from those elements that we see in our observations."
Importantly, Reeves and his colleagues did not detect iron, as might have been suspected in the wake of a supernova. This is likely because there had not been enough time for iron to form via radioactive decay, he said, implying that the time between the supernova and the GRB is very short.
"The new results strengthen the link between GRBs and supernovae, and favor models where the GRB occurs within a few days after the supernova," said Herman Marshall of MIT, in writing an analysis of the paper for the journal.
The findings are supported, Marshall said, by other recent detections of iron in the X-ray afterglows of gamma-ray bursts. These earlier observations, made by NASA's Chandra X-ray Observatory and the XMM-Newton, were not conclusive on their own.
The new study used data collected by the Italian-run BeppoSAX satellite and the European Space Agency's XMM-Newton.
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