GCN Circular 8611
Subject
Konus-Wind observation of GRB 081203A
Event
Date
2008-12-04T16:01:56Z (17 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, D. Svinkin, M. Ulanov,
and T. Cline, on behalf of the Konus-Wind team report:
The long GRB 081203A (Parsons et al., GCN 8595, Ukwatta et al., GCN
8599) was detected by Konus-Wind in the same trigger record as GRB
081203B (Copete et al., GCN 8600, 8602; Golenetskii et al., GCN 8610) at
~T0(KW)+260s.
(T0(KW)=49890.368 s UT (13:51:30.368). Correcting for the propagation
time delay from Wind to Swift of 0.7s, one sees that T0(BAT) corresponds
to T0(KW)+339.9s).
Since this burst occurred after the end of the time history record
(=T0(KW)+229s) we do not have the light curve of this GRB with good time
resolution. Instead we have KW multichannel spectra accumulated until
T0(KW)+490s (that is until T0(BAT)+150s), which were converted to a
3-band light curve with a time resolution of 8.192 s.
The burst light curve shows a weak emission starting at ~T0(BAT)-80s
(=T0(KW)+260s), the main double-peaked pulse starting at ~T0(BAT)-14s
(=T0(KW)+326s) and the decaying tail seen at least until T0(BAT)+134s
(=T0(KW)+474s).
As observed by Konus-Wind the burst
had a fluence of 3.05(-0.89, +1.40)x10^-5 erg/cm2
(in the 20 keV - 3 MeV energy range).
The time-integrated spectrum of the burst
(from T0(BAT)-79s to T0(BAT)+134 s) is well fitted
(in the 20 keV-3 MeV range) by a simple power law model
with index 1.54 +/- 0.08 (chi2 = 65.8/69 dof).
Fitting by a power law with exponential cutoff model:
dN/dE ~ (E^alpha)*exp(-E*(2+alpha)/Ep) yields
alpha = -1.33(-0.20, +0.27)
and Ep = 578(-290, +2398) keV (chi2 = 61.2/68 dof).
The spectrum of the main pulse
(from T0(BAT)-14s to T0(BAT)+52s) is well fitted
(in the 20 keV-3 MeV range) by a power law
with exponential cutoff model:
dN/dE ~ (E^alpha)*exp(-E*(2+alpha)/Ep)
with alpha = -1.29(-0.13, +0.15)
and Ep = 497(-156, +383) keV (chi2 = 66.2/68 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/GRB081203A/