TITLE:   GCN CIRCULAR
NUMBER:  23559
SUBJECT: Konus-Wind observation of GRB 181222A
DATE:    18/12/25 11:35:12 GMT
FROM:    Anna Kozlova at Ioffe Institute  <ann_kozlova@mail.ioffe.ru>

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

The long-duration GRB 181222A
(MAXI/GSC detection: Sakamaki et al., GCN Circ. 23547;
Fermi/GBM observation: Veres & Bissaldi, GCN Circ. 23548;
CGBM detection: Sakamoto et al., GCN Circ. 23553)
triggered Konus-Wind at T0=24090.989 s UT (06:41:30.989).

The burst light curve shows a multipeaked structure
started at ~T0-1.3 s with a total duration of ~171.5 s.
The emission is seen up to ~10 MeV.

As observed by Konus-Wind, the burst
had a fluence of 3.97(-0.33,+0.32)x10^-4 erg/cm2,
and a 64-ms peak flux, measured from T0+94.208 s,
of 6.71(-0.66,+0.66)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+146.688 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 = -1.05(-0.08,+0.08),
the high energy photon index beta = -1.90(-0.12,+0.09),
the peak energy Ep = 570(-100,+133) keV
(chi2 = 79/84 dof).

The spectrum near the maximum count rate
(measured from T0+93.440 to T0+96.000 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 = -0.87(-0.06,+0.06),
the high energy photon index beta = -2.01(-0.10,+0.08),
the peak energy Ep = 850(-114,+136) keV
(chi2 = 115/77 dof).

The Konus-Wind light curve of this GRB is available at
http://www.ioffe.ru/LEA/GRBs/GRB181222_T24090/

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