GCN Circular 10083
Subject
Konus-Wind and Konus-RF observations of GRB 091024
Date
2009-10-26T17:18:48Z (15 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, and D. Svinkin on behalf of
the Konus-Wind and Konus-RF teams, and
T. Cline on behalf of the Konus-Wind team, report:
The long GRB 091024 (Swift-BAT trigger #373674: Marshall et al. GCN
10062, Sakamoto et al. GCN 10072) was observed by Konus-Wind in the
waiting mode. The emission was detected in all three Konus-Wind energy
bands: G1 (18-70 keV), G2 (70-360 keV) and G3 (360-1360 keV) with high
S/N.
The burst light curve shows three pulses: the first pulse starts at
~T0-10 s and has a duration of ~90 s, the second starts at ~T0+600 s and
has a duration of ~100 s, and the most intense third pulse starts at
T0+840 s and has a duration of ~400 s; there is a low-level emission
between the first and second pulses.
The most intense part of the third pulse was also detected by Konus-RF,
while Coronas-F was exiting the SAA.
The GBM localizations suggest a common origin of these events (Bissaldi
& Connaughton, GCN 10070). Both the K-W light curve and the K-W ecliptic
latitude response confirms this suggestion. So, we believe all these
pulses belong to the extremely long burst, GRB 091024, which has a total
duration of ~1200 s. Hence, some optical observations of this burst were
performed during the most intense part of the prompt emission, but no
bright optical flares have been reported.
Modeling of the K-W 3-channel spectra by
a power law with exponential cutoff model:
dN/dE ~ E^(-alpha)*exp(-E*(2-alpha)/Ep)
yields the following parameters:
--------------------------------------------------
Tstart Tstop alpha Ep (keV)
--------------------------------------------------
P1 -7 80 -1.1+/-0.2 500+/-160
P2 606 703 -1.6+/-0.2 200+/-120
P3 835 1194 -1.4+/-0.2 230+/-50
Total -7 1194 -1.5+/-0.4 280+/-120
--------------------------------------------------
Tstart, Tstop - seconds since the BAT trigger time
As observed by Konus-Wind, the burst had a fluence of (1.13 +/-
0.12)x10^-4 erg/cm2 (in the 20 - 1300 keV energy range).
Assuming z = 1.092 (Cucchiara, Fox & Tanvir, GCN 10065) and a standard
cosmology model with H_0 = 70 km/s/Mpc, Omega_M=0.27, Omega_\Lambda =
0.7, the isotropic energy release E_iso ~3.2x10^53 erg.
All the quoted errors are estimated at the 1 sigma confidence level.
The K-W light curve of this burst is available at
http://www.ioffe.rssi.ru/LEA/GRBs/GRB091024/