TITLE:   GCN CIRCULAR
NUMBER:  16704
SUBJECT: Konus-Wind observation of GRB 140817A
DATE:    14/08/18 13:51:37 GMT
FROM:    Dmitry Frederiks at Ioffe Institute  <fred@mail.ioffe.ru>

S. Golenetskii, R.Aptekar, D. Frederiks, V. Pal'shin, P. Oleynik,
M. Ulanov, D. Svinkin, A. Tsvetkova, A.Lyssenko, and T. Cline
on behalf of the Konus-Wind team, report:

A long-duration GRB 140817A (Swift-BAT trigger 609736:
Sbarufatti et al., GCN 16695; Cummings et al., GCN 16699;
Fermi-GBM detection: Roberts & Meegan, GCN 16700)
triggered Konus-Wind at T0=25319.509 s UT (07:01:59.509).

The light curve shows a double-peaked structure from ~T0-0.5 s to ~T0+3.5 s,
the emission in this episode is visible up to ~8 MeV.
The subsequent broad, weak, soft pulse is visible in the instrument's
soft energy channel from ~T0+160 s to ~T0+270 s; it coincides in time with
the bright X-ray flare in the XRT light curve
(http://www.swift.ac.uk/xrt_products/00609736).

As observed by Konus-Wind, the burst had a fluence
of 3.4(-0.3,+0.3)x10^-6 erg/cm2, and a 64-ms peak flux,
measured from T0+2.816 s, of 3.0(-0.3,+0.3)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+8.448 s)
is best fit in the 20 keV - 15 MeV range
by the GRB (Band) function with the following model parameters:
the low-energy photon index alpha = -0.22 (-0.37,+0.40),
the high energy photon index beta = -2.8 (-7.2,+0.4),
the peak energy Ep = 118 (-18,+29) keV,
chi2 = 84/84 dof.

The Konus-Wind light curve of this GRB is available at
http://www.ioffe.ru/LEA/GRBs/GRB140817_T25319/

All the quoted errors are at the 95% confidence level.
All the quoted values are preliminary.