TITLE:   GCN CIRCULAR
NUMBER:  28495
SUBJECT: Konus-Wind observation of GRB 200914A
DATE:    20/09/25 14:29:03 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, hard-spectrum GRB 200914A
(Integral detection: Mereghetti et al., GCN 28419;
Fermi GBM observation: Dunwoody et al., GCN 28424;
AGILE detection: Ursi et al., GCN 28426)
triggered Konus-Wind at T0=46113.769 s UT (12:48:33.769).

The burst light curve shows a single pulse
which starts at ~T0-2.4 s and has a total duration of~38.0 s
The emission is seen up to ~2 MeV.

As observed by Konus-Wind, the burst
had a fluence of 4.26(-0.96,+1.08)x10^-5 erg/cm2,
and a 64-ms peak energy flux, measured from T0+0.306 s,
of 8.12(-2.44,+2.55)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+33.024 s)
is best fit in the 20 keV - 20 MeV range
by the GRB (Band) model with the following parameters:
the low-energy photon index alpha = -0.35(-0.34,+0.50),
the high energy photon index beta = -2.11(-0.70,+0.28),
the peak energy Ep = 461(-128,+201) keV,
chi2 = 93/97 dof.

The spectrum near the peak count rate
(measured from T0 to T0+8.448 s)
is best fit in the 20 keV - 1.6 MeV range
by a power law with exponential cutoff model:
dN/dE ~ (E^alpha)*exp(-E*(2+alpha)/Ep)
with  alpha = -0.58(-0.16,+0.19),
and Ep = 935(-170,+228) keV (chi2 = 86/98 dof).
Fitting by the GRB (Band) model yields the same alpha and Ep,
and an upper limit on the high energy photon index:
beta < -2.51 (chi2 = 86/97 dof).

The Konus-Wind light curve of this GRB is available at
http://www.ioffe.ru/LEA/GRBs/GRB200914_T46113/

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