TITLE:   GCN CIRCULAR
NUMBER:  39283
SUBJECT: Konus-Wind detection of GRB 250206A
DATE:    25/02/11 13:48:06 GMT
FROM:    Anna Ridnaia at Ioffe Institute <ridnaia@mail.ioffe.ru>

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

The long-duration GRB 250206A
(Fermi-GBM detection: Fermi GBM team, GCN 39172;
BALROG localization: Preis & Greiner, GCN 39173;
Fermi-LAT detection: Gupta et al., GCN 39233;
EIRSAT-1 GMOD detection: Murphy et al., GCN 39236)
triggered Konus-Wind at T0=71491.594 s UT (19:51:31.594).

The burst light curve shows two multipeaked episodes
started at ~T0-3.6 s with a total duration of ~75.6 s.
The emission is seen up to ~4 MeV.

The Konus-Wind light curve of this GRB is available at
http://www.ioffe.ru/LEA/GRBs/GRB250206_T71491/

As observed by Konus-Wind, the burst
had a fluence of 2.44(-0.09,+0.10)x10^-5 erg/cm2,
and a 64-ms peak flux, measured from T0+9.072 s,
of 2.91(-0.44,+0.44)x10^-6 erg/cm2/s
(both in the 20 keV - 10 MeV energy range).

The time-averaged spectrum of the burst
(measured from T0 to T0+73.984 s)
is best fit in the 20 keV - 10 MeV range
by a power law with exponential cutoff model:
dN/dE ~ (E^alpha)*exp(-E*(2+alpha)/Ep)
with alpha = -0.76(-0.10,+0.11)
and Ep = 205(-11,+13) keV (chi2 = 87/98 dof).
Fitting by a GRB (Band) model yields the same alpha and Ep,
and an upper limit on the high energy photon index: beta < -2.4
(chi2 = 85/97 dof).

The spectrum near the maximum count rate
(measured from T0+8.448 to T0+16.640 s)
is best fit in the 20 keV - 10 MeV range
by a power law with exponential cutoff model:
dN/dE ~ (E^alpha)*exp(-E*(2+alpha)/Ep)
with alpha = -0.06(-0.13,+0.13)
and Ep = 223(-9,+10) keV (chi2 = 85/82 dof).
Fitting by a GRB (Band) model yields the same alpha and Ep,
and an upper limit on the high energy photon index: beta < -3.4
(chi2 = 85/81 dof).

All the quoted errors are at the 68% confidence level.
All the quoted values are preliminary.