TITLE:   GCN CIRCULAR
NUMBER:  29130
SUBJECT: Konus-Wind detection of GRB 201221D (short)
DATE:    20/12/22 13:33:30 GMT
FROM:    Dmitry Frederiks at Ioffe Institute  <fred@mail.ioffe.ru>

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

The short GRB 201221D (Swift detection:  Page et al., GCN 29112)
triggered Konus-Wind (KW) at T0=83197.636 s UT (23:06:37.636).

The burst light curve shows a single pulse with the total duration of ~1.9 s (20-1500 keV).
The emission is seen up to ~1 MeV.

The Konus-Wind light curve of this GRB is available at
http://www.ioffe.ru/LEA/GRBs/GRB201221_T83197/

As observed by Konus-Wind, the burst had
a fluence of (5.3 ± 1.1)x10^-7 erg/cm^2 and
a 16-ms peak energy flux, measured from T0-0.016 s,
of (6.6 ± 1.3)x10^-6 erg/cm^2/s (both in the 20 keV - 10 MeV energy range).

The spectrum of the burst (measured from T0 to T0+0.128 s)
is best fit in the 20 keV - 1.5 MeV range
by a power law with exponential cutoff model:
dN/dE ~ (E^alpha)*exp(-E*(2+alpha)/Ep)
with  alpha = -0.95(-0.52,+0.64)
and Ep = 148(-37,+86) keV (chi2 = 19/20 dof).
Fitting by a GRB (Band) model yields the same alpha and Ep,
and an upper limit on the high energy photon index: beta < -2.1
(chi2 =19/19 dof).

All the quoted errors are estimated at the 90% confidence level.
All the presented results are preliminary.