A giant gamma-ray flare from the magnetar SGR 1806-20.
Two classes of rotating neutron stars-soft gamma-ray repeaters (SGRs) and anomalous X-ray pulsars-are magnetars, whose X-ray emission is powered by a very strong magnetic field (B approximately 10(15) G). SGRs occasionally become 'active', producing many short X-ray bursts. Extremely rarely, an SGR emits a giant flare with a total energy about a thousand times higher than in a typical burst. Here we report that SGR 1806-20 emitted a giant flare on 27 December 2004. The total (isotropic) flare energy is 2 x 10(46) erg, which is about a hundred times higher than the other two previously observed giant flares. The energy release probably occurred during a catastrophic reconfiguration of the neutron star's magnetic field. If the event had occurred at a larger distance, but within 40 megaparsecs, it would have resembled a short, hard gamma-ray burst, suggesting that flares from extragalactic SGRs may form a subclass of such bursts.
Palmer
D M
DM
Los Alamos National Laboratory, Los Alamos, New Mexico 87545, USA. palmer@lanl.gov
Barthelmy
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Gehrels
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Kippen
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Cayton
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Kouveliotou
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Eichler
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Wijers
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Woods
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Granot
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Lyubarsky
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Ramirez-Ruiz
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Barbier
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Chester
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Cummings
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Fenimore
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Finger
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Gaensler
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Hullinger
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Krimm
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Markwardt
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Nousek
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Parsons
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Patel
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Sakamoto
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Sato
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Suzuki
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Tueller
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