TITLE:   GCN CIRCULAR
NUMBER:  19554
SUBJECT: Konus-Wind observation of GRB 160623A
DATE:    16/06/23 17:25:59 GMT
FROM:    Dmitry Frederiks at Ioffe Institute  <fred@mail.ioffe.ru>

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

The very bright, long-duration GRB 160623A
(Fermi-LAT detection: Vianello et al., GCN 19553)
triggered Konus-Wind at T0=17977.594 s UT (04:59:37.594).

The light curve shows a broad pulse in the interval
from ~T0-25 s to ~T0+30 s, followed by a weaker emission
lasting until ~T0+200 s.
The emission is seen up to ~15 MeV.

As observed by Konus-Wind, the burst had a fluence
of 6.6(-0.1,+0.1)x10^-4 erg/cm2, and a 64-ms peak flux,
measured from T0+9.920 s, of 1.27(-0.03,+0.03)x10^-4 erg/cm2/s
(both in the 20 keV - 10 MeV energy range).

The time-averaged spectrum (measured from T0 to T0+38.912 s)
is best fit in the 50 keV - 15 MeV range
by the GRB (Band) function with the following model parameters:
the low-energy photon index alpha = -1.05 (-0.03,+0.03),
the high energy photon index beta = -2.67 (-0.10,+0.08),
the peak energy Ep = 562 (-23,+23) keV,
chi2 = 107/88 dof.

The spectrum near the peak count rate (measured from T0+7.936
to T0+11.776 s) is best fit in the 50 keV - 15 MeV range
by the GRB (Band) function with the following model parameters:
the low-energy photon index alpha = -0.88 (-0.05,+0.05),
the high energy photon index beta = -2.95 (-0.14,+0.11),
the peak energy Ep = 648 (-32,+33) keV,
chi2 = 104/88 dof.

The Konus-Wind light curve of this GRB is available at
http://www.ioffe.ru/LEA/GRBs/GRB160623_T11977/

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