GCN Circular 32783

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 221016A
(Fermi-GBM detection: Fermi GBM team, GCN#32773,
Bissaldi et al., GCN#32782;
Swift-BAT detection: Page et al., GCN#32774)
triggered Konus-Wind at T0=85166.713 s UT (23:39:26.713).

The burst light curve shows a single emission pulse
which starts at ~T0-1.7 s and has a total duration of ~12.5 s.
The emission is seen up to ~2 MeV.

The Konus-Wind light curve of this GRB is available at
http://www.ioffe.ru/LEA/GRBs/GRB221016_T85166/

As observed by Konus-Wind, the burst
had a fluence of 5.46(-0.74,+1.07)x10^-6 erg/cm2,
and a 64-ms peak flux, measured from T0+0.800 s,
of 1.87(-0.73,+0.74)x10^-6 erg/cm2/s
(both in the 20 keV - 10 MeV energy range).

The time-integrated spectrum of the burst
(measured from T0 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 = -1.02(-0.33,+0.40)
and Ep = 207(-46,+98) keV (chi2 = 60/99 dof).
Fitting by a GRB (Band) model yields the same alpha and Ep,
and an upper limit on the high energy photon index: beta < -2.0
(chi2 = 60/98 dof).

The spectrum near the maximum count rate
(measured from T0+0.256 to T0+8.448 s)
is best fit in the 20 keV - 10 MeV range
by a power law with exponential cutoff model
with  alpha = -0.89(-0.30,+0.35)
and Ep = 166(-26,+39) keV (chi2 = 81/96 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 = 81/95 dof).

All the quoted errors are at the 90% confidence level.
All the quoted values are preliminary.