GCN Circular 33061

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

The long GRB 221209A (Fermi-GBM observation: Bissaldi, GCN 33034
Not found
 
 
;
AstroSat CZTI detection: Gopalakrishnan et al., GCN Circ 33037;
IPN triangulation: Kozyrev et al., GCN 33059
Not found
 
 
)
triggered Konus-Wind (KW) at T0=21024.993 s UT (05:50:24.993).

The burst light curve shows a bright, FRED-like pulse,
which starts at ~T0-0.5 s, peaks at ~T0-0.640 s,
and has a total duration of ~10 s.
The emission is seen up to ~10 MeV.

The Konus-Wind light curve of this GRB is available at
http://www.ioffe.ru/LEA/GRBs/GRB221209_T21024/

As observed by Konus-Wind, the burst had
a fluence of (6.39 �� 0.43)x10^-5 erg/cm^2 and
a 64-ms peak energy flux, measured from T0 + 0.640 s,
of (4.89 �� 0.28)x10^-5 erg/cm^2/s (both in the 20 keV - 10 MeV energy range).

The time-integrated spectrum (measured from T0 to T0+12.302 s)
is best fit in the 20 keV - 15 MeV range
by a GRB (Band) function with the following model parameters:
the low-energy photon index alpha = -0.64 (-0.09,+0.10),
the high energy photon index beta = -2.05 (-0.08,+0.07),
the peak energy Ep = 306 (-32,+36) keV,
chi2 = 103/97 dof.

The spectrum near the peak count rate (measured from T0+0.256 to T0+1.280 s)
is best fit in the 20 keV - 15 MeV range
by a GRB (Band) function with the following model parameters:
the low-energy photon index alpha = -0.28 (-0.11,+0.12),
the high energy photon index beta = -1.97 (-0.07,+0.06),
the peak energy Ep = 366 (-39,+46) keV,
chi2 = 68/66 dof.

All the quoted errors are estimated at the 90% confidence level.
All the presented results are preliminary.