TITLE:   GCN CIRCULAR
NUMBER:  13552
SUBJECT: Konus-Wind observation of GRB 120728B
DATE:    12/07/31 14:19:25 GMT
FROM:    Dmitry Frederiks at Ioffe Institute  <fred@mail.ioffe.ru>

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

The long-duration intense GRB 120728B
(IPN detection and localization: Hurley at al., GCN 13549)
triggered Konus-Wind at T0=37534.985s UT (10:25:34.985)

The light curve shows multiple pulses in at least
three main bursting episodes.
The total duration of the burst is ~250 s,
the emission is seen up to 5 Mev.

The Konus-Wind light curve of this GRB is available at
http://www.ioffe.ru/LEA/GRBs/GRB120728_T37534/

As observed by Konus-Wind, the burst
had a fluence of 1.20(-0.15,+0.15)x10-4 erg/cm2,
and a 64-ms peak flux, measured from T0+57.472 s,
of 3.8(-0.4,+0.4)x10-6 erg/cm2/s
(both in the 20 keV - 10 MeV energy range).

The time-integrated spectrum of the main emission episode
(measured from T0 to T0+192.256 s)
is best fit in the 20 keV - 5 MeV range
by the GRB (Band) function with the following model parameters:
the low-energy photon index alpha = -1.3 (-0.1, +0.1),
the high energy photon index beta = -2.9 (-1.0, +0.3),
the peak energy Ep = 77(-5, +4) keV,
chi2 = 86.9/75 dof.

The spectrum at the maximum count rate
(measured from T0+55.552 to T0+64.256 s) is best fitted
is best fit in the 20 keV - 2 MeV range
by a power law with exponential cutoff model, for which:
alpha = -1.0 (-0.1, +0.1),
and Ep = 95(-4, +4) keV,
chi2 = 67.8/57 dof.


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