TITLE:   GCN CIRCULAR
NUMBER:  27316
SUBJECT: Konus-Wind observation of GRB200303A
DATE:    20/03/04 18:11:22 GMT
FROM:    Anastasia Tsvetkova at Ioffe Institute  <tsvetkova@mail.ioffe.ru>

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

The long-duration GRB200303A
(Swift detection of a burst: Cenko et al., GCN 27297;
Palmer et al., GCN 27311;
CALET Gamma-Ray Burst Monitor detection:
Asaoka et al., GCN 27301;
Fermi GBM observation: Malacaria & Meegan, GCN 27314)
triggered Konus-Wind at T0=9268.336 s UT (02:34:28.336).

The burst light curve shows a multi-peaked structure
which starts at ~T0-4.0 s and has a total duration of~67.1 s.
The emission is seen up to ~10 MeV.

As observed by Konus-Wind, the burst
had a fluence of 3.88(-1.20,+0.80)x10^-5 erg/cm2,
and a 64-ms peak energy flux, measured from T0+32.800 s,
of 2.38(-0.96,+1.15)x10^-6 erg/cm2/s
(both in the 20 keV - 10 MeV energy range).

The time-integrated spectrum of the burst
(measured from T0 to T0+65.792 s)
is best fit in the 20 keV - 3 MeV range
by the GRB (Band) model with the following parameters:
the low-energy photon index alpha = -1.25(-0.21,+0.28),
the high energy photon index beta = -2.17(-7.83,+0.18),
the peak energy Ep = 154(-44,+82) keV,
chi2 = 72/66 dof.

The spectrum near the peak count rate
(measured from T0+24.832 to T0+41.216 s)
is best fit in the 20 keV - 10 MeV range
by the GRB (Band) model with the following parameters:
the low-energy photon index alpha = -1.39(-0.14,+0.20),
the high energy photon index beta = -2.54(-7.46,+0.45),
the peak energy Ep = 183(-53,+54) keV,
chi2 = 80/86 dof.

The Konus-Wind light curve of this GRB is available at
http://www.ioffe.ru/LEA/GRBs/GRB200303_T09268/

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