GCN Circular 4599
Subject
Konus-Wind observation of GRB 060124
Event
Date
2006-01-25T18:41:43Z (20 years ago)
From
Valentin Pal'shin at Ioffe Inst <val@mail.ioffe.ru>
S. Golenetskii, R.Aptekar, E. Mazets, V. Pal'shin, D. Frederiks, and
T. Cline on behalf of the Konus-Wind team report:
The most intense part of the very long GRB 060124 (Swift-BAT trigger
#178750; Holland et al., GCN 4570; Fenimore et al., GCN 4586)
triggered Konus-Wind at T0=57853.894 s UT (16:04:13.894).
The propagation delay from Swift to Wind is 3.0 s for this GRB, i.e.,
correcting for this factor, one sees that the K-W trigger time
corresponds to the Swift-BAT trigger time T0(S-B) + 558.9 s.
The Konus-Wind light curve, recorded prior T0 in the waiting mode, shows
a weak precursor corresponding to the Swift-BAT trigger time,
no statistically significant emission in any K-W energy band from
~T0(S-B)+20 s to ~T0(S-B)+340 s, resuming emission at ~T0(S-B)+340 s, a
pulse at ~T0(S-B)+500 sec, the main double-peaked pulse from
~T0(S-B)+550 s to ~T0(S-B)+590 s, weaker pulses up to T0(S-B)+800 s.
The burst light curve resembles the light curves of two previously
detected very long bursts: GRB 041219a (Vestrand et al., Nature, 435,
178 (2005)), and GRB 050820a (Golenetskii et al., GCN 3852).
The spectrum integrated over the most intense part of the burst
(from T0 to T0+24.832 s) is well fitted (in the 20 keV - 2 MeV range)
by GRBM (Band) model for which:
the low-energy photon index is alpha = -1.29(-0.11,+0.14),
the high energy photon index beta = -2.25(-0.88,+0.27),
the break energy E0 = 335(-120,+177) keV (chi2 = 66/61 dof).
The fitting by a power law with exponential cutoff model:
dN/dE ~ E^(-alpha)*exp(-E*(2-alpha)/Ep)
in the same energy range gives
alpha = 1.355(-0.075,+0.085)
and Ep = 285(-56,+63) keV (chi2 = 70/62 dof).
As observed by Konus-Wind the burst had
a peak flux measured from T0+11.440 sec on 64 msec time scale
2.66(-0.69,+0.74)x10^-6 erg/cm2/sec,
and a fluence of the most intense part of the burst
1.43(-0.24,+0.28)x10^-5 erg/cm2
(both in the 20 keV - 2 MeV energy range).
All the quoted errors are at the 90% confidence level.
A preliminary estimation of the total burst fluence is ~2.80x10^-5
erg/cm2/sec (20 keV - 2 MeV). This value was derived by scaling the
fluence of the most intense part by the ratio between G2+G3 counts of
entire burst and the most intense part. Such scaling is justified
because G2/G3 hardness ratio is the same for the entire burst and the
most intense part (G2: 30-300 keV, G3: 300-1160 keV).
Assuming z = 2.297 (Cenko, Berger, and Cohen, GCN 4592 ) and a standard
cosmology model with H_0 = 70 km/s/Mpc, Omega_M = 0.3, Omega_\Lambda =
0.7, the isotropic energy release is E_iso ~3.4x10^53 erg,
the maximum luminosity is (L_iso)_max ~1.1x10^54 erg/s.
The Konus-Wind light curve of this GRB will be available
at http://www.ioffe.rssi.ru/LEA/GRBs/GRB060124_T57853/