TITLE:   GCN CIRCULAR
NUMBER:  8548
SUBJECT: Konus-Wind observation of GRB 081121
DATE:    08/11/23 16:07:29 GMT
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 081121 (Swift-BAT trigger #335105:
Oates et al., GCN 8537, Sakamoto et al. 8539) triggered
Konus-Wind at T0=74131.435 s UT (20:35:31.435).

The burst light curve shows a multipeaked structure with a total 
duration of ~18 s.

As observed by Konus-Wind the burst
had a fluence of 1.79(-0.31, +0.37)x10^-5 erg/cm2,
and a 256-ms peak flux measured from T0+16.368 s
of 2.60(-0.63, +0.70)x10^-6 erg/cm2/s
(both in the 20 keV - 7 MeV energy range).

The time-integrated spectrum of the burst
(from T0 to T0+16.640 s) is well be fitted (in the 20 keV - 7 MeV
range) by GRB (Band) model for which:
the low-energy photon index is alpha = -0.77(-0.14, +0.15),
the high energy photon index beta = -2.51(-0.66, +0.31),
the peak energy Ep = 248(-32, +38) keV (chi2 = 92.3/79 dof).

All the quoted errors are at the 90% confidence level.

Assuming z = 2.512 (Berger & Rauch, GCN 8542) 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 ~2.7x10^53 erg, the peak
luminosity (L_iso)_max ~ 1.4x10^53 erg/s, and Ep_rest ~870 keV.

The Konus-Wind light curve of this GRB is available
at http://www.ioffe.rssi.ru/LEA/GRBs/GRB081121_T74131/