Konus-Wind detection of GRB 210207B

The long GRB 210207B (Swift detection: Lien et al., GCN 29420) triggered Konus-Wind (KW) at T0=78768.813 s UT (21:52:48.813). The burst light shows a multi-peaked emission complex, which starts at ~T0-50 s, peaks at ~T0, and has the total duration of ~110 s. The emission in is seen up to ~2.5 MeV. The Konus-Wind light curve of this GRB is available at http://www.ioffe.ru/LEA/GRBs/GRB210207_T78768/ As observed by Konus-Wind, the burst had a fluence of (2.4 ± 0.8)x10^-5 erg/cm^2 and a 64-ms peak energy flux, measured from T0+1.472, of (4.5 ± 0.8)x10^-6 erg/cm^2/s (both in the 20 keV - 10 MeV energy range). The time-averaged spectrum (measured from T0 to T0+65.792 s) is best fit in the 20 keV - 15 MeV range by a power law with exponential cutoff (CPL) model: dN/dE ~ (E^alpha)*exp(-E*(2+alpha)/Ep) with alpha = -0.85(-0.34,+0.44) and Ep = 334(-97,+237) keV (chi2 = 91/97 dof). Fitting this spectrum by a Band function yields the same alpha and Ep, and an upper limit on the high energy photon index: beta < -2.15 (chi2 =67/97 dof). The spectrum near the peak count rate (measured from T0 to T0+8.448 s) is best fit in the 20 keV - 15 MeV range by the CPL model with alpha = -0.46(-0.22,+0.25) and Ep = 497(-84,+120) keV (chi2 = 76/97 dof). Fitting this spectrum by a Band function yields the same alpha and Ep, and an upper limit on the high energy photon index: beta < -2.33 (chi2 =76/96 dof). All the quoted errors are estimated at the 90% confidence level. All the presented results are preliminary.