Gamma-Ray Observations of a Giant Flare From the Magnetar Sgr 1806-20
/ Authors
D. Palmer, S. Barthelmy, N. Gehrels, R. Kippen, T. Cayton, C. Kouveliotou, D. Eichler, R. Wijers, P. Woods, J. Granot
and 18 more authors
Y. Lyubarsky, E. Ramirez-Ruiz, L. Barbier, M. Chester, J. Cummings, E. Fenimore, M. Finger, B. Gaensler, D. Hullinger, H. Krimm, C. Markwardt, J. Nousek, A. Parsons, S. Patel, T. Sakamoto, G. Sato, M. Suzuki, J. Tueller
/ Abstract
Magnetars comprise two classes of rotating neutron stars (Soft Gamma Repeaters (SGRs) and Anomalous X-ray Pulsars), whose X-ray emission is powered by an ultrastrong magnetic field, B {approx} 10{sup 15} G. Occasionally SGRs enter into active episodes producing many short X-ray bursts; extremely rarely (about once per 50 years per source), SGRs emit a giant flare, an event with total energy at least 103 higher than their typical bursts. Here we report that, on 2004 December 27, SGR 1806-20 emitted the brightest extra-solar transient event ever recorded, even surpassing the full moon brightness for 0.2 seconds. The total (isotropic) flare energy is 2 x 10{sup 46} erg, {approx}100 times higher than the only two previous events, making this flare a once in a century event. This colossal energy release likely occurred during a catastrophic reconfiguration of the magnetar's magnetic field. Such an event would have resembled a short, hard Gamma Ray Burst (GRB) if it had occurred within 40 Mpc, suggesting that extragalactic SGR flares may indeed form a subclass of GRBs.
Journal: Nature
DOI: 10.1038/nature03525