[vsnet-grb-info 25535] Konus-Wind observation of GRB 200422A

[GCN Circulars]

TITLE:   GCN CIRCULAR
NUMBER:  27635
SUBJECT: Konus-Wind observation of GRB 200422A
DATE:    20/04/24 13:49:14 GMT
FROM:    Dmitry Svinkin at Ioffe Institute  <svinkin at 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, very bright GRB 200422A
(IPN triangulation: Hurley et al., GCN Circ. 27626;
AstroSat-CZTI detection: Gupta et al., GCN Circ. 27630)
triggered Konus-Wind at T0=26537.847 s UT (07:22:17.847).

The burst light curve shows a multipeaked structure
which starts at ~T0-8.3 s and has a total duration of ~40 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/GRB200422_T26537/

As observed by Konus-Wind, the burst
had a fluence of 5.12(-0.15,+0.15)x10^-4 erg/cm2,
and a 64-ms peak flux, measured from T0+3.728 s,
of 1.42(-0.12,+0.12)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+38.656 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 = -0.67(-0.05,+0.05),
the high energy photon index beta = -1.94(-0.04,+0.04),
the peak energy Ep = 552(-38,+42) keV
(chi2 = 105/97 dof).

The spectrum near the maximum count rate
(measured from T0+3.584 to T0+4.096 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 = -0.63(-0.11,+0.12),
the high energy photon index beta = -1.89(-0.09,+0.07),
the peak energy Ep = 762(-138,+174) keV
(chi2 = 89/79 dof).

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