TITLE: GCN CIRCULAR NUMBER: 31802 SUBJECT: Konus-Wind observation of GRB 220320A DATE: 22/03/28 16:58:44 GMT FROM: Anastasia Tsvetkova at Ioffe Institute tsvetkova@mail.ioffe.ru

A. Tsvetkova,  D. Frederiks, D. Svinkin, M. Ulanov, A. Lysenko, A. Ridnaia and T. Cline on behalf of the Konus-Wind team, report:

The long-duration, bright GRB 220320A (AstroSat CZTI detection: Gopalakrishnan et al., GCN 31779; IPN triangulation: Kozyrev et al., GCN 31783) triggered Konus-Wind at T0=16796.141 s UT (04:39:56.141).

The burst light curve shows a multi-peaked structure which starts at ~T0-18.8 s and has a total duration of~52.8 s The emission is seen up to ~20 MeV.

As observed by Konus-Wind, the burst had a fluence of 6.05(-0.50,+0.52)x10^-5 erg/cm2, and a 64-ms peak energy flux, measured from T0+4.048 s, of 2.50(-0.34,+0.34)x10^-5 erg/cm2/s (both in the 20 keV - 10 MeV energy range).

The time-integrated spectrum of the burst (measured from T0 to T0+20.480 s) is best fit in the 20 keV - 20 MeV range by the GRB (Band) model with the following parameters: the low-energy photon index alpha = -0.84(-0.09,+0.10), the high energy photon index beta = -2.27(-0.15,+0.11), the peak energy Ep = 224(-21,+24) keV, chi2 = 100/97 dof.

The spectrum near the peak count rate (measured from T0 to T0+4.352 s) is best fit in the 20 keV - 20 MeV range by the GRB (Band) model with the following parameters: the low-energy photon index alpha = -0.43(-0.11,+0.12), the high energy photon index beta = -2.31(-0.17,+0.13), the peak energy Ep = 311(-29,+33) keV, chi2 = 67/86 dof.

The Konus-Wind light curve of this GRB is available at http://www.ioffe.ru/LEA/GRBs/GRB220320_T16796/

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