GCN Circular 10696

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 100423A (Swift-BAT trigger=420247;
Stroh et al., GCN 10651
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 ; Cummings et al., GCN 10658
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 )
triggered Konus-Wind at T0=02097.629s UT (00:34:57.629)

The burst light curve started with a hard short (~150 ms)
precursor followed (after ~0.6 s) by a FRED-like pulse
with a total duration of ~100 s.
The Konus-Wind light curve of this GRB is available at
http://www.ioffe.ru/LEA/GRBs/GRB100423_T02097/

As observed by Konus-Wind the burst
had a fluence of 4.8(+/-0.5)x10-5 erg/cm2,
and a 256-ms peak flux measured from T0+0.768s
of 8.3(+/-0.6)x10-6 erg/cm2/s
(both in the 20 keV - 2 MeV energy range).

The time-integrated spectrum of the burst
(from T0 to T0+65.792 s) is best fit
in the 20 keV - 2 MeV range by the GRB (Band)
model, for which:
the low-energy photon index alpha = -0.71 (-/+0.25),
the high energy photon index beta = -2.15 ( <-1.9 ),
the peak energy Ep = 455(-83, +194)keV (chi2 = 96/57 dof).

The spectrum at the maximum count rate
(measured from T0+0.256 to T0+8.848 s) is best fit
in the 20 keV - 2 MeV range by a power law
with exponential cutoff model, for which
alpha = -0.50(+/-0.15),
and Ep = 621(-67, +82) keV (chi2 = 74/58 dof).

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