GCN Circular 10817

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

The long GRB 100528A localized by SuperAGILE (Del Monte et al., GCN 
10810
Loading...
 
 ) triggered Konus-Wind at T0=6483.610 s UT (01:48:03.610).

The burst light curve shows a main pulse with a duration of ~30 s 
followed by a much weaker and softer pulse at ~T0+44 s with a duration 
of ~15 s.

As observed by Konus-Wind the burst
had a fluence of 2.85(-0.19, +0.21)x10^-5 erg/cm2,
and a 256-ms peak flux measured from T0+6.688 s
of 3.99(-0.58, +0.59)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+23.296 s) is well fitted (in the 20 keV - 2 MeV
range) by a power law with exponential cutoff model:
dN/dE ~ (E^alpha)*exp(-E*(2+alpha)/Ep), with
alpha = -1.28(-0.06, +0.07),  and
Ep = 382(-52, +69) keV (chi2 = 55.0/61 dof).
Fitting by a GRB (Band) model yields the same alpha and Ep,
and only an upper limit on the high energy
photon index: beta < -2.28 (chi2 = 55.0/60 dof).

The spectrum accumulated over the burst maximum (from T0 to T0+6.912 s) 
is well fitted (in the 20 keV - 2 MeV range)
by a power law with exponential cutoff model with
alpha = -1.18 +/- 0.07,  and
Ep = 558(-85, +115) keV (chi2 = 71.4/61 dof).
Fitting by GRB (Band) model yields the same alpha and Ep,
and only an upper limit on the high energy
photon index: beta < -2.43 (chi2 = 71.4/60 dof).

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

The Konus-Wind light curve of this GRB is available
at http://www.ioffe.ru/LEA/GRBs/GRB100528_T06483/