[vsnet-grb-info 11117] Konus-Wind observation of GRB 111103B

[GCN Circulars]

TITLE:   GCN CIRCULAR
NUMBER:  12532
SUBJECT: Konus-Wind observation of GRB 111103B
DATE:    11/11/05 13:12:31 GMT
FROM:    Dmitry Frederiks at Ioffe Institute  <fred at mail.ioffe.ru>

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

The long GRB 111103B (Swift-BAT trigger #505054:
Grupe et al., GCN 12519; Barthelmy et al., GCN 12524)
triggered Konus-Wind at T0=39541.020s UT (10:59:01.020)

The light curve shows a ~15 s long pulse followed by
a weaker activity continuing till ~(T0+40)s. The second group
of peaks observed by Swift/BAT after T0+100
is poorly determined in the Konus-Wind light curves
against the background of a rising M2.5 Solar flare.
The emission in the initial peak complex is seen up to ~4 MeV.
The Konus-Wind light curve of this GRB is available at
http://www.ioffe.ru/LEA/GRBs/GRB111103_T39541/

As observed by Konus-Wind the burst
had a fluence of (2.0 +/-0.3)x10-5 erg/cm2,
and a 256-ms peak flux, measured from T0+5.120 s,
of (2.7 +/-0.4)x10-6 erg/cm2/s
(both in the 20 keV - 5 MeV energy range).

The time-integrated spectrum of the burst
(measured from T0 to T0+41.216 s)
is best fitted in the 20 keV - 5 MeV range
by a power law with exponential cutoff model, for which
alpha = -0.97 (-0.18, +0.19),
and Ep = 372(-69, +109) keV,
chi2 = 77.2/77 dof.
Fitting this spectrum by the GRB (Band) function yields
the same alpha and Ep with a high energy photon index
beta < -2.2 (chi2 = 77.1/76 dof).

The spectrum at the maximum count rate
(measured from T0 to T0+6.144 s)
is best fitted in the 20 keV - 5 MeV range
by a power law with exponential cutoff model, for which
alpha = -0.97 (-0.12, +0.14),
and Ep = 393(-55, +76) keV,
chi2 = 70.2/77 dof.

All the observed properties are typical for a moderately intense
long gamma-ray burst and don't argue for a Galactic transient hypothesis.

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