TITLE:   GCN CIRCULAR
NUMBER:  31748
SUBJECT: Konus-Wind detection of GRB 220310A
DATE:    22/03/12 08:25:44 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 220310A
(MAXI/GSC detection: Negoro et al., GCN Circ. 31725;
CALET-CGBM detection: Negoro et al., GCN Circ. 31730)
triggered Konus-Wind at T0=1702.557 s UT (00:28:22.557).

The burst light curve shows an initial weak episode
which starts at ~T0-24 s and ends at ~T0-12 s,
followed by a brighter multipeaked structure
seen up to ~T0+37 s. The total burst duration is ~61 s.
The emission is seen up to ~7 MeV.

The Konus-Wind light curve of this GRB is available at
http://www.ioffe.ru/LEA/GRBs/GRB220310_T01702/

As observed by Konus-Wind, the burst
had a fluence of 3.15(-0.46,+0.54)x10^-5 erg/cm2,
and a 64-ms peak flux, measured from T0+14.144 s,
of 2.32(-0.62,+0.62)x10^-6 erg/cm2/s
(both in the 20 keV - 10 MeV energy range).

The time-averaged spectrum of the burst
(measured from T0 to T0+41.216 s)
is best fit in the 20 keV - 8 MeV range
by the GRB (Band) model with the following parameters:
the low-energy photon index alpha = -0.49(-0.37,+0.61),
the high energy photon index beta = -2.47(-0.67,+0.25),
the peak energy Ep = 138(-27,+32) keV
(chi2 = 75/85 dof).

The spectrum near the maximum count rate
(measured from T0+8.448 s to T0+16.640 s)
is best fit in the 20 keV - 8 MeV range
by a power law with exponential cutoff model:
with  alpha = -0.70(-0.24,+0.28)
and Ep = 168(-18,+23) keV (chi2 = 67/75 dof).
Fitting by a GRB (Band) model yields the same alpha and Ep,
and an upper limit on the high energy photon index: beta < -2.5
(chi2 = 67/74 dof).

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