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GCN Circular 6684

Subject
Intense burst from SGR 1806-20 detected on July 27
Date
2007-07-29T18:50:55Z (16 years ago)
From
Valentin Pal'shin at Ioffe Inst <val@mail.ioffe.ru>
S. Golenetskii, R. Aptekar, E. Mazets, V. Pal'shin, D. Frederiks,
and T. Cline on behalf of the Konus-Wind team,

A. von Kienlin, G. Lichti, A. Rau, D. Gotz, and S. Mereghetti,
on behalf of the INTEGRAL GRB team,

K. Yamaoka, T. Uehara, M. Ohno, Y. Fukazawa, T. Takahashi, M. Tashiro,
Y. Terada, T. Murakami, and K. Makishima
on behalf of the Suzaku WAM team,

K. Hurley, D. M. Smith, R. P. Lin, J. McTiernan, R. Schwartz, C. Wigger,
W. Hajdas, and A. Zehnder, on behalf of the RHESSI GRB team,
report:

An intense short SGR-like event triggered Konus-Wind
at 2007-07-27 T0=24046.498 s UT (06:40:46.498).
It was also detected by INTEGRAL-SPI-ACS, RHESSI,
and Suzaku-WAM in the TRN mode.
We have triangulated this burst to Konus-SPI-ACS
and Konus-RHESSI annuli, both of which are consistent
with the position of SGR 1806-20. The Konus-SPI-ACS annulus
is inconsistent with the positions of all other known SGRs.
The Konus ecliptic latitude response indicates that the source of the 
burst is near the ecliptic plane.
Thus we believe that this burst originated from SGR 1806-20.

The burst had a duration of ~1 s.
The Earth-crossing time of the onset was 24041 s UT (06:40:41).

As observed by Konus-Wind the burst had a fluence of
9.14(-0.44, +0.36)x10^-6 erg/cm2, and a 16-ms peak flux
measured from T0-0.050 s of (1.91 +/- 0.25)x10^-5 erg/cm2
(both in the 20-200 keV range).

The spectrum of the burst (from T0 to T0+0.256) is well fitted
(in the 20-200 keV range) by the OTTB spectral model:
dN/dE ~ E^{-1} exp(-E/kT)
with kT = 21.7 +/- 1.2 keV (chi2 = 25/20 dof).

All the quoted errors are at 90% c.l.

The Konus-Wind light curve of this burst is available
at http://www.ioffe.rssi.ru/LEA/SGRs/070727_T24046/

The last burst from SGR 1806-20 to trigger Konus-Wind
was on March 26 (Golenetskii et al., GCN 6228).
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