[vsnet-grb-info 12051] Konus-Wind observation of GRB 120709A

[GCN Circulars]

TITLE:   GCN CIRCULAR
NUMBER:  13440
SUBJECT: Konus-Wind observation of GRB 120709A
DATE:    12/07/11 11:55:36 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 120709A
(GBM trigger 120709883: Guiriec et al., GCN 13429;
Fermi/LAT detection: Kocevski et al., GCN 13423)
triggered Konus-Wind at T0=76303.609s UT (21:11:43.609)

The light curve shows multiple pulses grouped to three main episodes.
A total duration of the burst is ~25 s.

The emission is seen up to ~7 MeV.
The Konus-Wind light curve of this GRB is available at
http://www.ioffe.ru/LEA/GRBs/GRB120709_T76303/

As observed by Konus-Wind the burst
had a fluence of 1.8(-0.9,+1.0)x10-5 erg/cm2,
and a 64-ms peak flux, measured from T0+11.968 s,
of 6.4(-1.6,+2.5)x10-6 erg/cm2/s
(both in the 20 keV - 10 MeV energy range).

The time-integrated spectrum of the burst
(measured from T0 to T0+24.832 s)
is well fit in the 20 keV - 10 MeV range
by a power law with exponential cutoff model, for which:
alpha = -0.86 (-0.25, +0.31),
and Ep = 414(-117, +233) keV,
chi2 = 75.8/84 dof.
This spectrum is equally well fit by the GRB (Band) function
with the following model parameters:
the low-energy photon index alpha = -0.68 (-0.45, +0.56),
the high energy photon index beta = -2.0 (<-1.7),
the peak energy Ep = 296(-100, +356) keV,
chi2 = 75.4/83 dof.

The spectrum at the maximum count rate
(measured from T0+8.848 to T0+16.640 s)
is best fit in the 20 keV - 10 MeV range
by a power law with exponential cutoff model, for which:
alpha = -0.94 (-0.23, +0.28),
and Ep = 643(-216, +470) keV,
chi2 = 81.6/84 dof.

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