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The Amazing SGR 1806-20On 2004 December 27, the brightest gamma-ray flare ever recorded was detected by several instruments to be coming from the Soft Gamma Repeater SGR 1806-20. The flare even caused an ionospheric disturbance recorded around the globe by ionizing the Earth's upper atmosphere. SGRs belong to a class of slowly spinning (P = approx. 5-12 seconds) neutron stars with extremely high surface magnetic fields, B approx. 10(exp 15) G. The high magnetic fields of these objects were suggested by Duncan & Thompson, who called them "magnetars" to reflect the nature of the energy source that produces their quiescent and flaring X-ray luminosities. Very rarely, magnetars emit giant flares, extreme events with total energies typically approx. 10(exp 44) ergs, at least a factor of 1000 higher than the more frequent, repeating SGR bursts. Previously, only two giant flares have been recorded: from SGR 0526-66 in 1979 and from SGR 1900+14 in 1998. In this letter we report the detection of a very bright but rapidly fading radio afterglow that indicates a moderately relativistic expansion of plasma ejected from the magnetar. The radio afterglow is estimated to be at least 700 times brighter than that of the Aug 27 event, and is consistent with the hypothesis (also suggested by gamma-ray and X-ray data) that it was intrinsically a much more powerful event. I will discuss here the VLA results and their implications for the SGR flare energetics.
Document ID
20050167059
Acquisition Source
Marshall Space Flight Center
Document Type
Abstract
Authors
Kouveliotou, Chryssa
(NASA Marshall Space Flight Center Huntsville, AL, United States)
Date Acquired
August 23, 2013
Publication Date
January 1, 2005
Subject Category
Astronomy
Meeting Information
Meeting: 2005 SWIFT Team Meeting
Location: State College, PA
Country: United States
Start Date: March 1, 2005
End Date: March 2, 2005
Distribution Limits
Public
Copyright
Work of the US Gov. Public Use Permitted.

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