[vsnet-grb-info 12056] Konus-Wind observation of GRB 120707A

[GCN Circulars]

TITLE:   GCN CIRCULAR
NUMBER:  13445
SUBJECT: Konus-Wind observation of GRB 120707A
DATE:    12/07/11 18:30:58 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 hard intense GRB 120711A
(detected by the INTEGRAL/IBAS Gotz et al., GCN 13434;
MAXI/GSC detection: Serino et al., GCN 13436;
Fermi/GBM trigger 363667496/120711115: Gruber & Palassa, GCN 13437;
Fermi/LAT detection: Tam, Li & Kong, GCN 13444)
triggered Konus-Wind at T0=09955.810s UT (02:45:55.810)

The light curve starts with a precursor at ~T0-65s followed by
a strong hard double pulse lasting from ~T0-3 s to ~T0+50 s.
Several short (100 - 200 ms) bright spikes are well detected
over the general burst light curve in the ~T0+30 s to ~T0+40 s
time interval.
A a weak decaying emission tail in the soft energy channel
G1(25-90 keV) is detectable till at least ~T0+400s.
The emission during the main phase of the event is seen up to ~10 MeV.

The Konus-Wind light curve of this GRB is available at
http://www.ioffe.ru/LEA/GRBs/GRB120711_T09955/

As observed by Konus-Wind the burst
had a fluence of 3.8(-0.2,+0.2)x10-4 erg/cm2,
and a 64-ms peak flux, measured from T0+32.576 s,
of 3.6(-0.4,+0.4)x10-5 erg/cm2/s
(both in the 20 keV - 10 MeV energy range).

The time-integrated spectrum of the burst
(measured from T0 to T0+46.336 s)
is best fit in the 20 keV - 10 MeV range
with the GRB (Band) model, for which:
the low-energy photon index alpha = -0.97 (-0.02, +0.02),
the high energy photon index beta = -2.7 (-0.3, +0.2),
the peak energy Ep = 1060(-60, +60) keV,
chi2 = 95.7/87 dof.

The spectrum at the maximum count rate
(measured from T0+30.208 to T0+34.560 s)
is best fit in the 20 keV - 10 MeV range
with the GRB (Band) model, for which:
the low-energy photon index alpha = -0.93 (-0.04, +0.04),
the high energy photon index beta = -2.5 (-0.5, +0.3),
the peak energy Ep = 1400(-160, +170) keV,
chi2 = 85.5/87 dof.

Assuming the likely GRB redshift of z=1.405 (Tanvir et al., GCN 13441)
and a standard cosmology model with H_0 = 71 km/s/Mpc, Omega_M = 0.27, 
Omega_Lambda = 0.73:
the isotropic energy release E_iso is (1.95 ± 0.1)x10^54 erg,
the isotropic peak luminosity L_iso_max is (4.5 ± 0.5)x10^53 erg/s,
and Ep_rest is (2550 ± 150) keV.

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