An exceptionally bright flare from SGR 1806−20 and the origins of short-duration γ-ray bursts

Hurley, K.
Boggs, S. E.
Smith, D. M.
Duncan, R. C.
Lin, R.
Zoglauer, A.
Krucker, S.
Hurford, G.
Hudson, H.
Wigger, C.
Hajdas, W.
Thompson, C.
Mitrofanov, I.
Sanin, A.
Boynton, W.
Fellows, C.
von Kienlin, A.
Lichti, G.
Rau, A.
Cline, T.

¹UC Berkeley Space Sciences Laboratory, Berkeley, California 94720-7450, USA
²University of California, Department of Physics, Berkeley, California 94720, USA
³Physics Department and Santa Cruz Institute for Particle Physics, University of California, Santa Cruz, California 95064, USA
⁴University of Texas, Department of Astronomy, Austin, Texas 78712, USA
⁵Paul Scherrer Institute, 5232 Villigen PSI, Switzerland
⁶Canadian Institute of Theoretical Astrophysics, 60 St George Street, Toronto, Ontario M5S 3H8, Canada
⁷Space Research Institute (IKI), GSP7, Moscow 117997, Russia
⁸University of Arizona, Department of Planetary Sciences, Tucson, Arizona 85721, USA
⁹Max-Planck-Institut für extraterrestrische Physik, Giessenbachstrasse (Postfach 1312), 85748 (85741) Garching, Germany
¹⁰NASA Goddard Space Flight Center, Code 661, Greenbelt, Maryland 20771, USA

Received 7 February; accepted 4 March 2005; doi:10.1038/nature03519.

Supplementary Information accompanies the paper on www.nature.com/nature.

Correspondence and requests for materials should be addressed to K.H. ([email protected]).

Nature 434(7037):p 1098-1103, April 28, 2005.

Soft-γ-ray repeaters (SGRs) are galactic X-ray stars that emit numerous short-duration (about 0.1 s) bursts of hard X-rays during sporadic active periods. They are thought to be magnetars: strongly magnetized neutron stars with emissions powered by the dissipation of magnetic energy. Here we report the detection of a long (380 s) giant flare from SGR 1806−20, which was much more luminous than any previous transient event observed in our Galaxy. (In the first 0.2 s, the flare released as much energy as the Sun radiates in a quarter of a million years.) Its power can be explained by a catastrophic instability involving global crust failure and magnetic reconnection on a magnetar, with possible large-scale untwisting of magnetic field lines outside the star. From a great distance this event would appear to be a short-duration, hard-spectrum cosmic γ-ray burst. At least a significant fraction of the mysterious short-duration γ-ray bursts may therefore come from extragalactic magnetars.