TITLE:   GCN CIRCULAR
NUMBER:  32250
SUBJECT: Konus-Wind detection of GRB 220609B
DATE:    22/06/23 16:56:10 GMT
FROM:    Dmitry Frederiks at Ioffe Institute  <fred@mail.ioffe.ru>

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

The long GRB 220609B (CALET-CGBM detection: Asaoka et al., GCN Circ 32185;
AstroSat-CZTI detection: Gopalakrishnan et al., GCN Circ 32186;
IPN localization: Kozyrev et al., GCN 32190)
triggered Konus-Wind (KW) at T0=44473.865 s UT (12:21:13.865).

The burst light curve shows a single emission pulse
which starts at ~T0-1.5 s and has a total duration of ~18 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/GRB220609_T44473/

As observed by Konus-Wind, the burst had
a fluence of (1.0 ± 0.1)x10^-4 erg/cm^2 and
a 64-ms peak energy flux, measured from T0 + 4.544 s,
of (2.7 ± 0.2)x10^-5 erg/cm^2/s (both in the 20 keV - 10 MeV energy range).

The time-integrated spectrum (measured from T0 to T0+14.592 s)
is best fit in the 20 keV - 15 MeV range
by a GRB (Band) function with the following model parameters:
the low-energy photon index alpha = -0.79 (-0.11,+0.13),
the high energy photon index beta = -2.02 (-0.14,+0.10),
the peak energy Ep = 537 (-86,+112) keV,
chi2 = 113/98 dof.

The spectrum near the peak count rate (measured from T0 to T0+6.400 s)
is best fit in the 20 keV - 15 MeV range
by a GRB (Band) function with the following model parameters:
the low-energy photon index alpha = -0.83 (-0.06,+0.07),
the high energy photon index beta = -2.04 (-0.17,+0.12),
the peak energy Ep = 748 (-145,+170) keV,
chi2 = 88/97 dof.

All the quoted errors are estimated at the 90% confidence level.
All the presented results are preliminary.