TITLE:   GCN CIRCULAR
NUMBER:  28397
SUBJECT: Konus-Wind detection of GRB 200903E
DATE:    20/09/08 21:25:50 GMT
FROM:    Anna Ridnaia at Ioffe Institute  <ridnaia@mail.ioffe.ru>

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

The long-duration, very bright GRB 200903E
(AGILE detection: Ursi et al., GCN Circ. 28356;
AstroSat CZTI detection: Gupta et al., GCN Circ. 28367;
IPN triangulation: Hurley et al., GCN Circ. 28383)
triggered Konus-Wind at T0=9267.293 s UT (02:34:27.293).

The burst light curve shows a bright, multi-peaked structure
which started at ~T0-114.6 s and had a total duration of ~268.4 s.
The emission is seen up to ~6 MeV.

The Konus-Wind light curve of this GRB is available at
http://www.ioffe.ru/LEA/GRBs/GRB200903_T09267/

As observed by Konus-Wind, the burst
had a fluence of 4.84(-0.24,+0.23)x10^-4 erg/cm2,
and a 64-ms peak flux, measured from T0+20.464 s,
of 5.12(-0.57,+0.57)x10^-5 erg/cm2/s
(both in the 20 keV - 10 MeV energy range).

The time-averaged spectrum of the burst
(measured from T0 to T0+98.816 s)
is best fit in the 20 keV - 6 MeV range
by the GRB (Band) model with the following parameters:
the low-energy photon index alpha = -1.23(-0.03,+0.03),
the high energy photon index beta = -2.30(-0.14,+0.10),
the peak energy Ep = 413(-30,+33) keV
(chi2 = 100/74 dof).

The spectrum near the maximum count rate
(measured from T0+17.152 to T0+22.272 s)
is best fit in the 20 keV - 6 MeV range
by the GRB (Band) model with the following parameters:
the low-energy photon index alpha = -1.04(-0.05,+0.06),
the high energy photon index beta = -2.37(-0.35,+0.20),
the peak energy Ep = 717(-95,+106) keV
(chi2 = 74/71 dof).

All the quoted errors are at the 90% confidence level.
All the quoted values are preliminary.