TITLE:   GCN CIRCULAR
NUMBER:  34091
SUBJECT: Konus-Wind detection of GRB 230616A
DATE:    23/06/27 14:50:53 GMT
FROM:    Y. Temiraev at Ioffe Institute <yuri.temiraev@mail.ioffe.ru>

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

The short-duration, bright GRB 230616A
(Swift-BAT/GUANO detection: Tohuvavohu et al., GCN Circ. 33982;
AstroSat-CZTI detection: Waratkar et al., GCN Circ. 33983;
IPN triangulation: Kozyrev et al., GCN Circ. 34046)
triggered Konus-Wind at T0=74278.259 s UT (20:37:58.259).

The burst light curve shows a multipeaked structure
which starts at ~T0-30 ms and has a total duration of ~98 ms.
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/GRB230616_T74278/

As observed by Konus-Wind, the burst
had a fluence of 9.11(-1.11,+1.13)x10^-6 erg/cm2,
and a 16-ms peak flux, measured from T0+0.028 s,
of 1.77(-0.32,+0.33)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+0.064 s)
is best fit in the 20 keV - 7 MeV range
by a power law with exponential cutoff model:
dN/dE ~ (E^alpha)*exp(-E*(2+alpha)/Ep)
with alpha = -0.38(-0.15,+0.17)
and Ep = 1725(-257,+286) keV (chi2 = 63/55 dof).
Fitting by a GRB (Band) model yields the same alpha and Ep,
and an upper limit on the high energy photon index: beta < -2.7
(chi2 = 63/54 dof).

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