GCN Circular 9959
Subject
Konus-Wind and Konus-RF observations of GRB 090926A
Date
2009-09-28T16:42:28Z (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 bright GRB 090926A (Fermi-GBM trigger 275631628 / 090926181:
Bissaldi, GCN 9933) localized by Fermi-LAT (Uehara et al., GCN 9934)
triggered Konus-Wind at T0=15628.683 s UT (04:20:28.683).
It was also detected by Konus-RF instrument onboard CORONAS-PHOTON s/c
in the waiting mode while being at high latitudes.
The burst light curve shows a multipeaked structure with a total
duration of ~16 s, followed by a weak tail seen up to ~T0+50 s.
As observed by Konus-Wind the burst
had a fluence of 1.80(-0.07, +0.08)x10^-4 erg/cm2,
and a 16-ms peak flux measured from T0+8.944 s
of 2.91(-0.54, +0.56)x10^-5 erg/cm2/s
(both in the 20 keV - 10 MeV energy range).
The time-integrated spectrum of the burst
(from T0 to T0+26.880 s) can be fitted (in the 20 keV - 10 MeV
range) by GRB (Band) model for which:
the low-energy photon index alpha = -0.76 +/- 0.03,
the high energy photon index beta = -2.59(-0.13, +0.10),
the peak energy Ep = 321 +/- 12 keV (chi2 = 106.0/84 dof).
The emission is clearly seen up to ~10 MeV.
All the quoted errors are at the 90% confidence level.
Assuming z = 2.1062 (Malesani et al., GCN 9942)
and a standard cosmology model with H_0 = 70 km/s/Mpc, Omega_M = 0.27,
Omega_\Lambda = 0.73, the isotropic energy release E_iso ~2.0x10^54 erg,
the peak luminosity (L_iso)_max ~ 1.0x10^54 erg/s, and Ep_rest ~1000 keV.
The Konus-Wind light curve of this GRB is available
at http://www.ioffe.ru/LEA/GRBs/GRB090926_T15628/