TITLE:   GCN CIRCULAR
NUMBER:  21679
SUBJECT: Konus-Wind observation of GRB 170822A
DATE:    17/08/24 15:43:32 GMT
FROM:    Dmitry Svinkin at Ioffe Institute  <svinkin@mail.ioffe.ru>

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

The long-duration, soft-spectrum GRB 170822A
(Swift-BAT detection: Melandri et al., GCN Circ. 21640)
triggered Konus-Wind at T0=33111.022 s UT (09:11:51.022).

The burst light curve shows a multipeaked structure
which starts at ~T0-10.5 s and has a total duration of ~62 s.
The emission is seen up to ~1 MeV.

The Konus-Wind light curve of this GRB is available at
http://www.ioffe.ru/LEA/GRBs/GRB170822_T33111/

As observed by Konus-Wind, the burst
had a fluence of 8.57(-0.76,+0.88)x10^-6 erg/cm2,
and a 64-ms peak flux, measured from T0+0.266 s,
of 1.66(-0.60,+0.60)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+57.6 s)
is best fit in the 20 keV - 2 MeV range
by a power law with exponential cutoff model:
dN/dE ~ (E^alpha)*exp(-E*(2+alpha)/Ep)
with  alpha = -1.20(-0.38,+0.48)
and Ep = 70(-12,+12) keV (chi2 = 57/62 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 = 55/61 dof).

The spectrum near the maximum count rate
(measured from T0 to T0+8.448 s)
is best fit in the 20 keV - 2 MeV range
by a power law with exponential cutoff model:
with  alpha = -1.17(-0.26,+0.30)
and Ep = 90(-11,+13) keV (chi2 = 51/61 dof).
Fitting by a GRB (Band) model yields the same alpha and Ep,
and an upper limit on the high energy photon index: beta < -2.8
(chi2 = 51/60 dof).

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