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Some results were previewed yesterday in Science Express describing research on an exceptionally unusual gamma ray flash: unusual because it has lasted for two and a half months! In fact, this flash, named Sw 1644+57, is still detected, even though much fainter than when first seen by the Swift satellite on March 28th.
Even more incredible is the fact that, according to the person following most closely the event, Joshua Bloom (University of California, Berkeley), the gamma and X-ray emission will probably not cease until next year!
This makes it immediately clear that we aren't talking about a normal Gamma-Ray Burst (GRB), that last only up to a few minutes and are thought to be generated by the gravitational collapse of very massive stars or by the coalescence of two bodies that have already collapsed.
According to Bloom, the event that generated the flash is extremely rare: a star that gets pulled apart and shredded as it falls into a black hole a million times more massive. The violent journey of the remains of the star around the accretion disk generates a huge amount of energy. The two figures above illustrate the process.
All of this is happening in an anonymous galaxy 3.8 billion light years away, that evidently hosts a super-massive black hole at its centre (as do most galaxies) that had remained quiescent until 24th or 25th March (for us Earthlings!). Then, the fall of the stellar material towards the black hole generated the bi-polar jets, typical of sources with accretion disks, through which it released its tremendous energy: the research team led by Bloom estimate that 10% of the stellar mass will have been converted into energy.
Some speculative estimates of how frequent these kind of events might be observed are once every 100 million years in a given galaxy (with a super-massive black hole). Having caught this event very soon after its start, giving the opportunity to follow the event for its entire duration, provides an extremely valuable source of information on the behaviour of black holes.
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