Konus-Wind observation of GRB 190706C

The long-duration, very bright GRB 190706C (IPN triangulation: Svinkin et al., GCN 25035; CALET Gamma-Ray Burst Monitor detection: Sakamoto et al., GCN 25038) 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.