GCN Circular 8926
Subject
Konus-Wind observation of bright short GRB 090227B
Date
2009-03-03T16:01:32Z (16 years ago)
From
Valentin Pal'shin at Ioffe Inst <val@mail.ioffe.ru>
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 bright short hard GRB 090227B (Fermi/GBM trigger 257452263 /
090227772: Guiriec, GCN 8921) localized by IPN (Golenetskii et al., GCN
8925) triggered Konus-Wind at T0=66659.079 s UT (18:30:59.079).
As observed by Konus-Wind the burst
had a fluence of (2.75 +/- 0.27)x10^-5 erg/cm2,
and a 16-ms peak flux measured from T0+0.008 s
of 3.98(-0.58, +0.59)x10^-4 erg/cm2/s
(both in the 20 keV - 10 MeV energy range).
The time-integrated spectrum of the burst
(from T0 to T0+0.192 s) is well fitted (in the 20 keV - 10 MeV
range) by a power law with exponential cutoff model:
dN/dE ~ (E^alpha)*exp(-E*(2+alpha)/Ep)
with alpha = -0.43(-0.09, +0.10),
and Ep = 2253(-262, +292) keV (chi2 = 29.4/47 dof).
Fitting by GRB (Band) model yields:
the low-energy photon index alpha = -0.41(-0.10, +0.12),
the high energy photon index beta < -2.5,
the peak energy Ep = 2134(-326, +332) keV (chi2 = 28.1/46 dof).
The emission is clearly seen up to 10 MeV.
All the quoted errors are at the 90% confidence level.