[vsnet-grb-info 18201] Konus-Wind observation of GRB 160703A

[GCN Circulars]

TITLE:   GCN CIRCULAR
NUMBER:  19649
SUBJECT: Konus-Wind observation of GRB 160703A
DATE:    16/07/04 11:31:52 GMT
FROM:    Dmitry Frederiks at Ioffe Institute  <fred at mail.ioffe.ru>

D. Frederiks, S. Golenetskii, R.Aptekar, P. Oleynik, M. Ulanov,
D. Svinkin, A. Tsvetkova, A.Lysenko, A. Kozlova, and T. Cline,
on behalf of the Konus-Wind team, report:

The long GRB 160703A (Swift/BAT observation:
Cenko et al., GCN 19645; Lien et al., GCN 19648)
triggered Konus-Wind at T0=43807.015 s UT (12:10:07.015).

The light curve shows multiple overlapping pulses, a total
duration of the burst is ~50 s.
The emission is seen up to ~4 MeV.

As observed by Konus-Wind, the burst had a fluence of
(2.7 ± 0.2)x10^-5 erg/cm2 and a 64-ms peak energy flux,
measured from T0+23.360, of (2.8 ± 0.3)x10^-6 erg/cm2
(both in the 20 keV - 10 MeV energy range).

The time-integrated spectrum (measured from T0 to T0+41.216 s)
is best fit in the 20 keV - 10 MeV range by a cutoff power-law
(CPL) function with the following model parameters:
the photon index alpha = -1.01(-0.09,+0.10),
and the peak energy Ep = 327(-36,+46) keV,
chi2 = 93/97 dof.
Fitting this spectrum with the GRB (Band) function yields
the same alpha and Ep with only an upper limit on beta of -2.4,
chi2 = 93/96 dof.

The spectrum near the peak count rate (measured from T0 to T0+41.216 s)
is best fit in the 20 keV - 10 MeV range by a cutoff power-law
(CPL) function with the following model parameters:
the photon index alpha = -0.66(-0.15,+0.16),
and the peak energy Ep = 272(-29,+35) keV,
chi2 = 79/89 dof.
Fitting this spectrum with the GRB (Band) function yields
the same alpha and Ep with only an upper limit on beta of -3.1,
chi2 = 79/88 dof.

The Konus-Wind light curve of this GRB is available at
http://www.ioffe.ru/LEA/GRBs/GRB160703_T43807/

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