[vsnet-grb-info 13889] Konus-Wind observation of GRB 130907A

[GCN Circulars]

TITLE:   GCN CIRCULAR
NUMBER:  15203
SUBJECT: Konus-Wind observation of GRB 130907A
DATE:    13/09/09 10:52:42 GMT
FROM:    Dmitry Frederiks at Ioffe Institute  <fred at 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 intense GRB 130907A
(Swift-BAT trigger 569992: Page, et al., GCN 15183;
Cummings, et al., GCN 15202)
triggered Konus-Wind at T0=77955.997 s UT (21:39:15.997),
or ~118 s before the BAT trigger.

The burst light curve shows multiple bright, partially overlapped
pulses from ~T0-4 s till ~T0+210~s.
The emission is seen up to ~15 MeV.

The Konus-Wind light curve of this GRB is available at
http://www.ioffe.ru/LEA/GRBs/GRB130907_T77955/

As observed by Konus-Wind, the burst
had a fluence of (7.9 ± 0.5)x10-4 erg/cm2,
and a 256-ms peak flux, measured from T0+139.008 s,
of (2.2 ± 0.1)x10-5 erg/cm2/s
(both in the 20 keV - 10 MeV energy range).

The time-averaged spectrum (measured from T0 to T0+206.080 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 = -0.91 ± 0.02,
the high energy photon index beta = -2.42 ± 0.07,
the peak energy Ep = 394 ± 11 keV,
chi2 = 90/92 dof.

The spectrum near the maximum count rate
(measured from T0+139.264 s to T0+143.872 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 = -0.65 ± 0.03,
the high energy photon index beta = -2.22 ± 0.05,
the peak energy Ep = 390 ± 16 keV,
chi2 = 111/96 dof.

Assuming the NOT redshift z=1.238 (de Ugarte Postigo, et al., GCN 15187),
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 of GRB 130907A:
the isotropic energy release E_iso is (3.3 ± 0.1)x10^54 erg,
the peak luminosity L_iso is (2.0 ± 0.1)x10^53 erg/s,
and the rest-frame peak energy Ep,i = (880 ± 25) keV

All the quoted results are preliminary.