TITLE:   GCN CIRCULAR
NUMBER:  29426
SUBJECT: Konus-Wind detection of GRB 210207B
DATE:    21/02/08 13:36:32 GMT
FROM:    Dmitry Frederiks at Ioffe Institute  <fred@mail.ioffe.ru>

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

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.