TITLE:   GCN CIRCULAR
NUMBER:  11021
SUBJECT: Konus-Wind observation of GRB 100728A
DATE:    10/07/28 18:02:30 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 GRB 100728A
(Swift/BAT trigger 430151: Canizzo et.al, GCN 11004)
triggered Konus-Wind at T0=8300.008s UT (02:18:20.008)

The burst light curve shows a complex structure with
a total duration of ~200 s. There is a hint of a weaker
emission lasting at least to T0+290 s.
The emission is seen up to several MeV.
The Konus-Wind light curve of this GRB is available at
http://www.ioffe.ru/LEA/GRBs/GRB100728_T08300/

As observed by Konus-Wind the burst
had a fluence of 1.95(+/-0.35)x10-4 erg/cm2,
and a 256-ms peak flux, measured from T0+27.392s,
of 4.2(+/-0.7)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+137.216 s) is best fit
in the 20 keV - 10 MeV range by the GRB (Band)
model, for which:
the low-energy photon index alpha = -0.65 (-0.09, +0.09),
the high energy photon index beta = -2.5 (-0.3, +0.2),
the peak energy Ep = 305(-25, +27)keV (chi2 = 88/84 dof).

The spectrum at the maximum count rate
(measured from T0+24.832 to T0+31.488 s) is best fit
in the 20 keV - 10 MeV range by the GRB (Band)
model, for which:
the low-energy photon index alpha = -0.47 (+/-0.15),
the high energy photon index beta = -2.6 (-0.3, +0.2),
the peak energy Ep = 390(-48, +63)keV (chi2 = 84/84 dof).

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