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GCN Circular 26614

Subject
Konus-Wind observation of GRB 191227A
Date
2019-12-30T13:13:35Z (4 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 long-duration GRB 191227A
(Fermi-GBM detection: The Fermi GBM team, GCN Circ. 26593;
Swift-BAT detection: Melandri et al., GCN Circ. 26595;
Stamatikos et al., GCN Circ. 26608;
Fermi-LAT detection: Fana Dirirsa et al., GCN Circ. 26598)
triggered Konus-Wind at T0=5970.414 s UT (01:39:30.414).

The burst light curve shows a multi-peaked structure
which starts at ~T0-27 s and has a total duration of ~52 s.
The emission is seen up to ~10 MeV.

The Konus-Wind light curve of this GRB is available at
http://www.ioffe.ru/LEA/GRBs/GRB191227_T05970/

As observed by Konus-Wind, the burst
had a fluence of 1.02(-0.08,+0.09)x10^-4 erg/cm2,
and a 64-ms peak flux, measured from T0+8.096 s,
of 1.86(-0.35,+0.36)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+29.440 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 = -0.70(-0.12,+0.13),
the high energy photon index beta = -2.28(-0.16,+0.12),
the peak energy Ep = 275(-26,+30) keV
(chi2 = 102/97 dof).

The spectrum near the maximum count rate
(measured from T0+6.400 to T0+13.056 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 = -0.65(-0.18,+0.22),
the high energy photon index beta = -2.25(-0.22,+0.15),
the peak energy Ep = 266(-40,+46) keV
(chi2 = 82/97 dof).

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