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GCN Circular 6228

long burst from SGR 1806-20 detected on March 26
2007-03-28T13:02:07Z (17 years ago)
Valentin Pal'shin at Ioffe Inst <>
S. Golenetskii, R. Aptekar, E. Mazets, V. Pal'shin, D. Frederiks,
and T. Cline on behalf of the Konus-Wind 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, report:

A bright long SGR-like event triggered the Konus-Wind
at T0=1447.725 (00:24:07.725) on March 26.
It was also detected by the Suzaku-WAM in the TRN mode.
We have triangulated it to an annulus centered at
RA(J2000) = 186.083 (12h 24m 20s)  Dec(J2000)=+3.334 (+3d 20' 04"),
whose radius is 87.186 +/- 1.090 deg (3 sigma).
As the center line of this annulus passes 0.311 degrees (0.9 sigma)
from the position of SGR 1806-20
and the Konus ecliptic latitude response indicates
that the source of the burst is near the ecliptic plane,
we believe that this burst originated from SGR 1806-20.

The shape of the burst light curve is typical for SGR bursts,
but with an unusually long duration. It demonstrates a fast rise
and a ~8-s decay with a bump at T-T0 ~5 s.

As observed by Konus-Wind the burst had a fluence
2.78(-0.08, +0.07)x10^-5 erg/cm2, and a peak flux on 16-ms time scale
2.01(-0.26, +0.25)x10^-5 erg/cm2 (both in the 20-200 keV range).

The time-integrated spectrum of the burst can be fit by the OTTB
spectral model:
dN/dE ~ E^{-1} exp(-E/kT)
with kT = 20.7 +/- 0.7 keV, which is typical for SGR 1806-20.

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

The Konus-Wind light curve of this GRB can be seen

A previous SGR burst triggered Konus-Wind
on March 17 at T0=84623.793 s UT (23:30:23.793).
It had a duration of ~4 sec.
The burst was not localized, but since the Konus ecliptic
latitude response indicates that the burst source is near the ecliptic 
plane, we believe that it also originated from SGR 1806-20.

The longest burst from SGR 1806-20 (except the giant burst)
had a duration of ~22 sec (Golenetskii et al., GCN 4312).
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