X-ray fireworks could signal supernovae

Trio of flashes fuel gamma ray debate

NASA astronomers last month detected two X-ray blasts and an almost-gamma ray burst that could be signs of imminent supernovae.

The X-ray flashes came on 12 and 16 September, followed on 24 September by something the scientists describe as being "on the cusp" of being a gamma ray burst. The three events were detected in different regions in space using NASA's High-Energy Transient Explorer (HETE-2) satellite.

"Each burst has been beautiful," said Dr. George Ricker, who headed the research team at MIT. "Depending on how these evolve, they could support important theories about supernovae and gamma-ray bursts."

Other science teams around the world are now training their scopes on the regions, waiting for any changes. If the flashes are followed by supernovae, astronomers will have a new early warning tool, and will be able to study the explosions themselves in much more detail.

But they could be even more useful.

Gamma-ray bursts are the most powerful explosions we have detected since the Big Bang, and are closely linked to supernovae: astronomers think many of them are caused by massive stars collapsing into black holes, or from neutron stars merging. Either event is thought to produce two, narrow jets of energy, shooting off in opposite directions.

X-ray flashes, however, are not yet conclusively associated with supernova explosions. Some scientists speculate that an X-ray flash is a gamma ray burst viewed off-centre, while others hold that the two phenomena are totally separate.

If the X-ray flares are followed by the final collapse of the stars in question, then astronomers may be able to conclude that gamma ray bursts and X-ray flares are indeed linked.

Even better, the X-ray flashes are much closer to Earth than the gamma ray bursts. If they do turn out to be precursors of a supernova, scientists will be able to study the process in unprecedented detail. ®

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