TITLE:   GCN CIRCULAR
NUMBER:  15368
SUBJECT: Konus-Wind observation of GRB 131011B
DATE:    13/10/24 17:52:37 GMT
FROM:    Dmitry Frederiks at Ioffe Institute  <fred@mail.ioffe.ru>

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 131011B
(Swift-BAT trigger 574266: Beardmore, et al., GCN 15323;
IPN triangulation: Hurley at al., GCN 15366)
triggered Konus-Wind at T0=80208.914 s UT (22:16:48.914).

The burst light curve shows a broad multi-peaked pulse from ~T0-35 s
till ~T0+40 s.
The emission is seen up to ~12 MeV.

The K-W ecliptic latitude response indicates the source located
at medium-to-high Northern ecliptic latitude,
which is at odds with the BAT position reported in GCN 15323,
however, consistent with the recent IPN box (GCN 15366).

The Konus-Wind light curve of this GRB is available at
http://www.ioffe.ru/LEA/GRBs/GRB131014_T80208/

As observed by Konus-Wind, the burst
had a fluence of (7.7 ± 0.3)x10-5 erg/cm2,
and a 64-ms peak flux, measured from T0+2.212 s,
of (6.0 ± 0.6)x10-6 erg/cm2/s
(both in the 20 keV - 10 MeV energy range).

The time-averaged spectrum (measured from T0 to T0+31.744 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 = -0.68 ± 0.06,
the high energy photon index beta = -2.21 ± 0.09,
the peak energy Ep = 270 ± 18 keV,
chi2 = 110/97 dof.

The spectrum near the maximum count rate
(measured from T0 to T0+7.936 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 = -0.63 ± 0.04,
the high energy photon index beta = -2.22 ± 0.14,
the peak energy Ep = 331 ± 33 keV,
chi2 = 131/97 dof.

All the quoted values are preliminary.