TITLE:   GCN CIRCULAR
NUMBER:  18413
SUBJECT: Konus-Wind observation of GRB 151006A
DATE:    15/10/08 11:04:52 GMT
FROM:    Anastasia Tsvetkova at Ioffe Institute  <tsvetkova@mail.ioffe.ru>

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

The long-duration, hard-spectrum GRB 151006A
(Swift-BAT trigger #657750: Kocevski et al., GCN 18398;
Cummings  et al., GCN 18409;
Fermi GBM detection: Roberts & Meegan, GCN 18404)
triggered Konus-Wind at T0=35697.746 s UT (09:54:57.746).

The burst light curve shows a single FRED-like pulse
with a total duration of ~114 s.
The emission is seen up to ~10 MeV.

As observed by Konus-Wind, the burst
had a fluence of 5.30(-0.87,+0.92)x10^-5 erg/cm2,
and a 64-ms peak energy flux, measured from T0+2.928 s,
of 5.60(-2.26,+2.23)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+73.984 s)
is best fit in the 20 keV - 15 MeV range
by the GRB (Band) model with the following parameters:
the low-energy photon index alpha = -1.26(-0.23,+0.42),
the high energy photon index beta = -1.73(-0.13,+0.09),
the peak energy Ep = 223(-132,+514) keV,
chi2 = 85/97 dof.

The spectrum near the peak count rate
(measured from T0 to T0+8.448 s)
is best fit in the 20 keV - 15 MeV range
by a power law with exponential cutoff model:
dN/dE ~ (E^alpha)*exp(-E*(2+alpha)/Ep)
with  alpha = -1.40(-0.06,+0.07),
and Ep = 2600(-1200,+2900) keV (chi2 = 71/98 dof).
Fitting by the GRB (Band) model yields the same alpha and Ep,
and an upper limit on the high energy photon index:
beta < -1.7 (chi2 = 71/97 dof).

The Konus-Wind light curve of this GRB is available at
http://www.ioffe.ru/LEA/GRBs/GRB151006_T35697/

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