GCN Circular 42487
Subject
Konus-Wind detection of GRB 251022A
Event
Date
2025-10-27T17:16:14Z (3 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 GRB 251022A (Fermi-GBM detection: The Fermi GBM team, GCN 42380;
Mukherjee & Meegan, GCN 42410;
Fermi-LAT detection: Di Lalla et al., GCN 42384;
SVOM/GRM observation: Ren et al., GCN 42484)
triggered Konus-Wind (KW) at T0=81287.312 s UT (22:34:47.312).
The burst consists of multiple emission pulses
in the interval from T0-35 s to T0+90;
the total duration of the burst is ~125 s.
The Konus-Wind light curve of this GRB is available at
http://www.ioffe.ru/LEA/GRBs/GRB251022_T81287/
As observed by Konus-Wind, the burst had
a fluence of (4.14 ± 0.71)x10^-5 erg/cm^2 and
a 64-ms peak energy flux, measured from T0 + 23.168 s,
of (1.09 ± 0.36)x10^-5 erg/cm^2/s (both in the 20 keV - 10 MeV energy range).
The time-integrated spectrum (measured from T0 to T0+90.368 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 = -1.37 (-0.08,+0.07),
the high energy photon index beta = -2.06 (-0.22,+0.13),
the peak energy Ep = 178 (-38,+80) keV,
chi2 = 96/97 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 a GRB (Band) function
with the following model parameters:
the low-energy photon index alpha = -0.71 (-0.42,+0.80),
the high energy photon index beta = -2.13 (-0.84,+0.24),
the peak energy Ep = 161 (-56,+84) keV,
chi2 = 91/97 dof.
All the quoted errors are estimated at the 68% confidence level.
All the presented results are preliminary.