GCN Circular 40977
Subject
Konus-Wind detection of GRB 250703A
Event
Date
2025-07-05T14:50:15Z (2 days ago)
From
Dmitry Frederiks at Ioffe Institute <fred@mail.ioffe.ru>
Via
email
D. Frederiks, A.Lysenko, A. Ridnaia, D. Svinkin,
A. Tsvetkova, M. Ulanov, and T. Cline,
on behalf of the Konus-Wind team, report:
The long-duration GRB 250703A (Fermi-GBM detection:
The Fermi GBM team, GCN 40909;
IPN localization Kozyrev et al., GCN 40976)
triggered Konus-Wind (KW) at T0=32851.983 s UT (09:07:31.983).
The burst light curve shows a single multi-peaked emission pulse
with a total duration of ~4.5 s.
The emission is seen up to ~5 MeV.
The Konus-Wind light curve of this GRB is available at
http://www.ioffe.ru/LEA/GRBs/GRB250703_T32851/
As observed by Konus-Wind, the burst had
a fluence of (5.86 ± 0.66)x10^-6 erg/cm^2 and
a 64-ms peak energy flux, measured from T0 + 0.960 s,
of (3.81 ± 0.43)x10^-6 erg/cm^2/s (both in the 20 keV - 10 MeV energy range).
The time-integrated spectrum (measured from T0 to T0+8.448 s)
is best fit in the 20 keV - 15 MeV range by a GRB (Band) function
with the following model parameters:
the low-energy photon index alpha = -0.36 (-0.22,+0.28),
the high energy photon index beta = -2.76 (-0.49,+0.27),
the peak energy Ep = 147(-15,+15) keV,
chi2 = 84/94 dof.
All the quoted errors are estimated at the 68% confidence level.
All the presented results are preliminary.