GCN Circular 20141

D. Frederiks, S. Golenetskii, R.Aptekar, P. Oleynik, M. Ulanov,
D. Svinkin, A. Tsvetkova, A.Lysenko, A. Kozlova, and T. Cline,
on behalf of the Konus-Wind team, report:

A very long-duration GRB 161103A has been detected
by Konus-Wind in the waiting mode starting from ~T0=82000 UT
(22:46:40) on November 3, 2016.

The burst was seen almost equally well in both KW detectors,
so its source is close to the ecliptic plane.
We note, that the location of the IceCube event 161103 (GCN 20119
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 ),
which occurred ~ 14 hours before GRB 161103 is also at low
ecliptic latitude (~ -3.1 deg). According to the GOES data,
there was no prominent solar X-ray activity at the time of the burst.

The event light curve shows several peaks in the interval
from ~T0-300 s to ~T0+4400 s. The total burst duration,
~4700 s, makes this event an ultra-long GRB candidate.
The spectral hardness of the emission is rather high at
the beginning of the event and decreases with the development
of the burst.

As observed by Konus-Wind, the burst had a fluence of
(3.0 �� 0.15)x10^-4 erg/cm2 and a 2.944-s peak energy flux,
measured from ~T0+160 s, of (8.6 �� 4.6)x10^-7 erg/cm2
(both in the 20 - 1500 keV energy range).

The time-integrated 3-channel spectrum of the burst, measured from
T0-310 s to T0+4400 s, is well described by a simple power law
function with the PL index of 1.72 �� 0.04.
The spectrum near the peak count rate, measured from T0+110s
to T0+174 s, can be modeled by a power law with exponential
cutoff (CPL) with alpha = -0.41 �� 0.45, and Ep = 925 �� 345 keV.

The K-W light curve of this burst is available at
http://www.ioffe.rssi.ru/LEA/GRBs/GRB161103A/

All the quoted errors are estimated at the 1 sigma confidence level.
All the presented results are preliminary.