[vsnet-grb-info 13250] Konus-Wind observation of GRB 130504C

[GCN Circulars]

TITLE:   GCN CIRCULAR
NUMBER:  14587
SUBJECT: Konus-Wind observation of GRB 130504C
DATE:    13/05/06 11:08:40 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-duration intense GRB 130504C
(Fermi-LAT detection: Kocevski et al., GCN 14574;
Fermi-GBM detection: Burgess et al., GCN 14583)
triggered Konus-Wind at T0=84544.491s UT (23:29:04.491)

The light curve shows multiple partly overlapped peaks
from ~T0-15 s to ~T0+105s.
The emission is seen up to 12 MeV.

A possible hard precursor is seen in the 360-1400 keV
light curve at ~T0-50s, but its attribution to GRB 130504C
is yet unclear.

The Konus-Wind light curve of this GRB is available at
http://www.ioffe.ru/LEA/GRBs/GRB130504_T84544/

As observed by Konus-Wind, the burst
had a fluence of (2.0 ± 0.1)x10-4 erg/cm2,
and a 64-ms peak flux, measured from T0+21.440s,
of (2.6 ± 0.2)x10-5 erg/cm2/s
(both in the 20 keV - 10 MeV energy range).

The time-integrated spectrum (measured from T0 to T0+105.216 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 = -1.32 ± 0.04,
the high energy photon index beta = -2.15 ± 0.1,
the peak energy Ep = 452 ± 49 keV,
chi2 = 110/97 dof.

The spectrum at the maximum count rate
(measured from T0+21.248 to T0+23.296 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 = -0.74 ± 0.12,
the high energy photon index beta = -1.93 ± 0.06,
the peak energy Ep = 251 ± 38 keV,
chi2 = 61/66 dof.

All the quoted results are preliminary.