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GCN Circular 29196

Subject
Konus-Wind observation of GRB 201227A
Date
2020-12-29T16:42:04Z (3 years ago)
From
Dmitry Svinkin at Ioffe Institute <svinkin@mail.ioffe.ru>
D. Svinkin, S. Golenetskii, R. Aptekar, D. Frederiks,
M. Ulanov, A. Tsvetkova, A. Lysenko, A. Ridnaia, and T. Cline
on behalf of the Konus-Wind team, report:

The short-duration, very bright GRB 201227A
(AGILE detection: Ursi et al., GCN Circ. 29179;
IPN triangulation: Svinkin et al., GCN Circ. 29182;
Insight-HXMT/HE detection: Xiao et al., GCN Circ. 29187)
triggered Konus-Wind at T0=54846.705 s UT (15:14:06.705).

The burst light curve shows a multipeaked structure
which starts at ~T0-28 ms and has a total duration of ~106 ms.
The emission is seen up to ~4 MeV.

The Konus-Wind light curve of this GRB is available at
http://www.ioffe.ru/LEA/GRBs/GRB201227_T54846/

As observed by Konus-Wind, the burst
had a fluence of 4.30(-0.52,+0.54)x10^-6 erg/cm2,
and a 16-ms peak flux, measured from T0,
of 1.05(-0.18,+0.18)x10^-4 erg/cm2/s
(both in the 20 keV - 10 MeV energy range).

The time-averaged spectrum of the burst
(measured from T0 to T0+0.064 s)
is best fit in the 20 keV - 4 MeV range
by a power law with exponential cutoff model:
dN/dE ~ (E^alpha)*exp(-E*(2+alpha)/Ep)
with  alpha = -0.17(-0.18,+0.21)
and Ep = 870(-130,+151) keV (chi2 = 17/19 dof).
Fitting by a GRB (Band) model yields the same alpha and Ep,
and an upper limit on the high energy photon index: beta < -2.3
(chi2 = 17/18 dof).

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