TITLE:   GCN CIRCULAR
NUMBER:  31723
SUBJECT: Konus-Wind detection of GRB 220308A
DATE:    22/03/09 22:19:58 GMT
FROM:    Dmitry Svinkin at Ioffe Institute  <svinkin@mail.ioffe.ru>

D. Svinkin, 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 220308A
(IPN triangulation: Svinkin et al., GCN Circ. 31715;
Swift/BAT-GUANO detection: Tohuvavohu et al., GCN Circ. 31716;
CALET-CGBM detection: Marrocchesi et al., GCN Circ. 31719)
triggered Konus-Wind at T0=20585.134 s UT (05:43:05.134).

The burst light curve shows a multipeaked structure
which starts at ~T0-0.1 s and has a total duration of ~69 s.
The emission is seen up to ~15 MeV.

The Konus-Wind light curve of this GRB is available at
http://www.ioffe.ru/LEA/GRBs/GRB220308_T20585/

As observed by Konus-Wind, the burst
had a fluence of 2.87(-0.11,+0.11)x10^-4 erg/cm2,
and a 64-ms peak flux, measured from T0+1.296 s,
of 1.06(-0.10,+0.10)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+22.016 s)
is best fit in the 20 keV - 16 MeV range
by the GRB (Band) model with the following parameters:
the low-energy photon index alpha = -0.93(-0.02,+0.02),
the high energy photon index beta = -3.42(-6.58,+0.47),
the peak energy Ep = 1099(-55,+57) keV
(chi2 = 130/97 dof).

The spectrum near the maximum count rate
(measured from T0+1.024 to T0+1.536 s)
is best fit in the 20 keV - 16 MeV range
by the GRB (Band) model with the following parameters:
the low-energy photon index alpha = -0.26(-0.09,+0.10),
the high energy photon index beta = -3.13(-1.01,+0.41),
the peak energy Ep = 1419(-150,+155) keV
(chi2 = 69/66 dof).

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