[vsnet-grb-info 1944] Detection of an intermediate burst from SGR 1806-20 on August 8

[GCN Circulars]

TITLE:   GCN GRB OBSERVATION REPORT
NUMBER:  3782
SUBJECT: Detection of an intermediate burst from SGR 1806-20 on August 8
DATE:    05/08/10 14:42:12 GMT
FROM:    Valentin Pal'shin at Ioffe Inst  <val at mail.ioffe.ru>

S. Golenetskii, R.Aptekar, E. Mazets, V. Pal'shin, D. Frederiks
on behalf of Konus-Wind and Helicon/Coronas-F teams, and
T. Cline on behalf of the Konus-Wind team report:

A SGR-like burst 050808 triggered Konus-Wind 
at 67438.919 s UT (18:43:58.919).
It was also detected by Helicon-Coronas-F in the waiting mode.
We have triangulated it to a wide annulus centered at
RA(2000) = 302.888 deg, Decl(2000) = -22.871 deg,
whose radius is 31.070 ± 3.188 deg (3 sigma).
As the center line of this annulus passes 2.46 degrees (2.3 sigma)
from the position of SGR 1806-20
and the Konus ecliptic latitude response indicates
that the source of the burst is near ecliptic plane,
we believe that this burst originated from SGR 1806-20.

The burst had a duration of ~1.1 sec,
fluence (6.9 ± 0.2)10-6 erg/cm2,
and peak flux on 64-ms time scale (1.2 ± 0.3)10-5 erg/cm2 s
(both in 20-200 keV range).
The burst light curve demonstartes nearly linear decline
during ~1 s (the burst rise was missed by Konus-Wind;
the total burst duration was estimated combining the K-W background
and trigger data).

The time-integrated spectrum of the burst can be fitted by the OTTB
spectral model:
dN/dE ~ E^{-1} exp(-E/kT),
with kT = 18.5 ± 0.8 keV.