GCN Circular 15452

S. Golenetskii, R.Aptekar, D. Frederiks, V. Pal'shin,
P. Oleynik, M. Ulanov, D. Svinkin, and T. Cline on behalf
of the Konus-Wind team, report:

The long-duration GRB 131105A
(Swift-BAT trigger 576738: Cummings et al., GCN 15446
Not found
 
 
)
triggered Konus-Wind at T0=7527.233 s UT (02:05:27.233).

The burst light curve shows multiple peaks in the time
interval from ~T0-35 s till ~T0+90 s.
The emission is seen up to ~3 MeV.

The Konus-Wind light curve of this GRB is available at
http://www.ioffe.ru/LEA/GRBs/GRB131105_T07527/

As observed by Konus-Wind, the burst
had a fluence of (2.3 � 0.2)x10-5 erg/cm2,
and a 64-ms peak flux, measured from T0+1.600 s,
of (2.0 � 0.2)x10-6 erg/cm2/s
(both in the 20 keV - 10 MeV energy range).

The time-averaged spectrum (measured from T0 to T0+90.368 s)
is best fit in the 20 keV - 15 MeV range
by the GRB (Band) function with the following model parameters:
the low-energy photon index alpha = -0.88 � 0.38,
the high energy photon index beta = -2.33 � 0.33,
the peak energy Ep = 156 � 38 keV,
chi2 = 97/96 dof.

The spectrum near the maximum count rate
(measured from T0 to T0+8.448 s)
is best fit in the 20 keV - 15 MeV range
by the GRB (Band) function with the following model parameters:
the low-energy photon index alpha = -1.04 � 0.27,
the high energy photon index beta = -2.64 � 0.76,
the peak energy Ep = 174 � 41 keV,
chi2 = 87.9/97 dof.

Assuming the redshift z=1.686 (Xu, et al., GCN 15450
Not found
 
 
)
and a standard cosmology model with H_0 = 70 km/s/Mpc,
Omega_M = 0.27, and Omega_Lambda = 0.73,
we estimate the following rest-frame parameters:
the isotropic energy release E_iso is (1.7 � 0.1)x10^53 erg,
the peak luminosity L_iso is (4.0 � 0.4)x10^52 erg/s,
and the rest-frame peak energy Ep,i = (420 � 100) keV

All the quoted values are preliminary.