[vsnet-grb-info 20829] Konus-Wind observation of GRB 180703A

[GCN Circulars]

TITLE:   GCN CIRCULAR
NUMBER:  22927
SUBJECT: Konus-Wind observation of GRB 180703A
DATE:    18/07/08 12:38:41 GMT
FROM:    Dmitry Frederiks at Ioffe Institute  <fred at mail.ioffe.ru>

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

The long GRB 180703A (IPN Triangulation: Hurley et al., GCN 22925;
Fermi-LAT detection: Racusin et al., GCN 22883;
Fermi-GBM detection: Poolakkil & Meegan, GCN 22896)
triggered Konus-Wind at T0=75705.256 s UT (21:01:45.256)/

The burst light curve shows a single, FRED-like pulse
with a total duration of ~50 s. Also, there is a weak
count rate increase in the softest KW light curve around T0 + 170 s.
The emission in the main peak is seen up to ~10 MeV.

As observed by Konus-Wind, the burst had a fluence of
(4.1 ± 1.0)x10^-5 erg/cm2 and a 64-ms peak energy flux,
measured from T0+1.728, of (8.9 ± 1.3)x10^-6 erg/cm2
(both in the 20 keV - 10 MeV energy range).

The time-integrated spectrum (measured from T0 to T0+49.408 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 = -0.85 (-0.21,+0.33),
the high energy photon index beta = -1.89 (-0.37,+0.19),
the peak energy Ep = 367 (-136,+196) keV,
chi2 = 89/97 dof.

The spectrum near the peak count rate (measured from T0
to T0+8.448 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 = -0.73 (-0.17,+0.20),
the high energy photon index beta = -1.90 (-0.22,+0.13),
the peak energy Ep = 407 (-97,+147) keV,
chi2 = 88/97 dof.

The Konus-Wind light curve of this GRB is available at
http://www.ioffe.ru/LEA/GRBs/GRB180703_T75705/

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