GCN Circular 25042

A. Tsvetkova, S. Golenetskii, R.Aptekar, D. Frederiks,
M. Ulanov, D. Svinkin, A. Lysenko, A. Kozlova and T. Cline
on behalf of the Konus-Wind team, report:

The long-duration, very bright GRB 190706C
(IPN triangulation: Svinkin et al., GCN 25035
Not found
 
 
;
CALET Gamma-Ray Burst Monitor detection: Sakamoto et al., GCN 25038
Not found
 
 
)
triggered Konus-Wind at T0=49348.84 s UT (13:42:28.840).

The burst light curve shows a multi-peaked structure
with a total duration of ~6.5 s.
The emission is seen up to ~2 MeV.

As observed by Konus-Wind, the burst
had a fluence of 2.52(-0.17,+0.20)x10^-5 erg/cm2,
and a 64-ms peak energy flux, measured from T0+2.640 s,
of 1.80(-0.19,+0.19)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+3.072 s)
is best fit in the 20 keV - 2 MeV range
by the GRB (Band) model with the following parameters:
the low-energy photon index alpha = -0.56(-0.09,+0.10),
the high energy photon index beta = -3.09(-0.70,+0.35),
the peak energy Ep = 281(-20,+19) keV,
chi2 = 34/56 dof.

The spectrum near the peak count rate
(measured from T0+2.048 to T0+3.072 s)
is best fit in the 20 keV - 3 MeV range
by a power law with exponential cutoff model:
dN/dE ~ (E^alpha)*exp(-E*(2+alpha)/Ep)
with�� alpha = -0.39(-0.12,+0.13),
and Ep = 288(-19,+22) keV (chi2 = 53/51 dof).
Fitting by the GRB (Band) model yields the same alpha and Ep,
and an upper limit on the high energy photon index:
beta < -2.86 (chi2 = 52/50 dof).

The Konus-Wind light curve of this GRB is available at
http://www.ioffe.ru/LEA/GRBs/GRB190706_T49348/

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