학술논문
GEOTAIL observation of the SGR1806-20 Giant Flare: The first 600 ms
Document Type
Working Paper
Author
Terasawa, Toshio; Tanaka, Yasuyuki; Takei, Yasuhiro; Kawai, Nobuyuki; Yoshida, Atsumasa; Nomoto, Ken'ichi; Yoshikawa, Ichiro; Saito, Yoshifumi; Kasaba, Yasumasa; Takashima, Takeshi; Mukai, Toshifumi; Noda, Hirotomo; Murakami, Toshio; Watanabe, Kyoko; Muraki, Yasushi; Yokoyama, Takaaki; Hoshino, Masahiro
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Subject
Language
Abstract
On December 27, 2004, plasma particle detectors on the GEOTAIL spacecraft detected an extremely strong signal of hard X-ray photons from the giant flare of SGR1806-20, a magnetar candidate. While practically all gamma-ray detectors on any satellites were saturated during the first ~500 ms interval after the onset, one of the particle detectors on GEOTAIL was not saturated and provided unique measurements of the hard X-ray intensity and the profile for the first 600 ms interval with 5.48 ms time resolution. After ~50 ms from the initial rapid onset, the peak photon flux (integrated above ~50 keV) reached the order of 10^7 photons sec^{-1} cm^{-2}. Assuming a blackbody spectrum with kT=175 keV, we estimate the peak energy flux to be 21 erg sec^{-1} cm^{-2} and the fluence (for 0-600 ms) to be 2.4 erg cm^{-2}. The implied energy release comparable to the magnetic energy stored in a magnetar (~10^{47} erg) suggests an extremely efficient energy release mechanism.
Comment: 6 pages, 2 color figures, submitted to Nature
Comment: 6 pages, 2 color figures, submitted to Nature