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GCN Circular 2769

Subject
Konus-Wind observation of a series SGR 1806-20 bursts on 041005
Date
2004-10-06T14:53:29Z (20 years ago)
From
Dmitry Frederiks at Ioffe Institute <fred@mail.ioffe.ru>
S. Golenetskii, R.Aptekar, E. Mazets, V. Pal'shin, D. Frederiks and
T. Cline on behalf of the Konus-Wind team, report:

A series of more than 24 short soft bursts triggered Konus-Wind at
50209.639 s UT (13:56:49.639) Observation of this event by the INTEGRAL
IBIS/ISGRI attributed it to SGR 1806-20 (GCN 2763, 2764).
This series resembles the series of soft bursts from SGR 1900+14
detected on 1998 May 30, three months before giant outburst on 1998
August 27.
http://www.ioffe.rssi.ru/LEA/SGR/Catalog/Data/1900/980530a.htm
(Aptekar et al., ApJSS v. 137, p. 227)

The series consists of two very crowded clusters:
from -0.512 s to 17 s and
from 165 to 200 s since trigger time
(numereous weaker bursts are seen between intense bursts).
The total fluence of the bursts is approximately 8.6e-5 ergs/cm2
in 20-200 keV range.

The most intense burst started at 7 s after trigger time.
It had a duration of ~0.25s and peak flux of 5.7e-5 ergs/cm2 s
(in the 20-200 keV range).

The spectra of the bursts can be fitted by the OTTB spectral model:
dN/dE ~ E^{-1} exp(-E/kT).
The spectrum of the starting burst has kT = 19+/-1 keV,
the spectrum which includes the most intense burst
has kT = 21.1+/-0.6 keV. These values of kT are typical for this SGR.

The time-integrated spectrum of the second cluster of the events
from 170 s to 195 s has kT = 28+/-1 keV that exceeds the
typical kT for this SGR.
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