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 soft GRB 110420A (Swift-BAT trigger #451757: Mangano et al.,
GCN 11941; Krimm et al., GCN 11945) triggered Konus-Wind at
T0(KW)=39750.543 s UT (11:02:30.543).
The burst light curve shows a single pulse started at ~T0(KW)-9 s with a
duration of ~18 s.
As observed by Konus-Wind the burst
had a fluence of 6.54(-0.53, +0.64)x10^-6 erg/cm2,
and a 256-ms peak flux measured from T0-0.320 s
of (1.11 +/- 0.17)x10^-6 erg/cm2/s
(both in the 20 - 500 keV energy range).
The time-integrated spectrum of the burst
(from T0 to T0+8.448 s) is well fitted (in the 20 - 500 keV
range) by a power law with exponential cutoff model:
dN/dE ~ (E^alpha)*exp(-E*(2+alpha)/Ep)
with alpha = -1.71(-0.26, +0.31),
and Ep = 43(-18, +17) keV (chi2 = 31.1/39 dof).
Fitting by GRB (Band) model yields the same alpha and Ep,
and an upper limit on the high energy
photon index: beta < -2.61 (chi2 = 31.1/38 dof).
All the quoted errors are at the 90% confidence level.
The Konus-Wind light curve of this GRB is available