TITLE:   GCN CIRCULAR
NUMBER:  19417
SUBJECT: Konus-Wind observation of GRB 160509A
DATE:    16/05/10 12:44:04 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 160509A
(Fermi-LAT detection: Longo et al., GCN 19403;
MAXI/GSC detection: Ono et al., GCNs 19404;
Fermi-GBM detection: Roberts, Fitzpatrick & Veres, GCN 19411)
triggered Konus-Wind at T0=32326.696 s UT (08:58:46.696).

The light curve shows a broad, multi-peaked pulse in the interval
from ~T0-10 s to ~T0+30 s, followed by several weaker emission
episodes until ~T0+380 s.
The emission is seen up to ~15 MeV.

As observed by Konus-Wind, the burst had a fluence
of 2.90(-0.35,+0.35)x10^-4 erg/cm2, and a 64-ms peak flux,
measured from T0+12.096 s, of 2.8(-0.2,+0.2)x10^-5 erg/cm2/s
(both in the 20 keV - 10 MeV energy range).

The time-averaged spectrum (measured from T0 to T0+370.944 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 = -0.99 (-0.08,+0.10),
the high energy photon index beta = -2.08 (-0.17,+0.12),
the peak energy Ep = 288 (-45,+48) keV,
chi2 = 51.3/97 dof.

The spectrum near the peak count rate (measured from T0+11.264
to T0+12.800 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 = -0.71 (-0.07,+0.07),
the high energy photon index beta = -2.27 (-0.14,+0.11),
the peak energy Ep = 311 (-32,+35) keV,
chi2 = 96.7/77 dof.

The Konus-Wind light curve of this GRB is available at
http://www.ioffe.ru/LEA/GRBs/GRB160509_T32326/

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