GCN Circular 41166
Subject
Konus-Wind detection of GRB 250725A
Event
Date
2025-07-25T15:53:14Z (3 months ago)
Edited On
2025-07-25T17:11:22Z (3 months ago)
From
Dmitry Frederiks at Ioffe Institute <fred@mail.ioffe.ru>
Edited By
Judith Racusin at NASA/GSFC <judith.racusin@nasa.gov> on behalf of Dmitry Frederiks at Ioffe Institute <ddfrederiks@gmail.com>
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 250725A (Fermi-GBM detection:
The Fermi GBM team, GCN 41150;
Swift detection: Evans et al., GCN 41152;
SVOM/GRM observation: Wang et al., GCN 41164)
triggered Konus-Wind (KW) at T0=6698.029 s UT (01:51:38.029).
The burst shows a multi-peaked structure with a total duration of ~12 s.
The emission is seen up to ~1.5 MeV.
The Konus-Wind light curve of this GRB is available at
http://www.ioffe.ru/LEA/GRBs/GRB250725_T06698/
As observed by Konus-Wind, the burst had
a fluence of (1.19 ± 0.10)x10^-5 erg/cm^2 and
a 64-ms peak energy flux, measured from T0 + 0.512 s,
of (4.16 ± 0.41)x10^-6 erg/cm^2/s (both in the 20 keV - 10 MeV energy range).
The time-integrated spectrum (measured from T0 to T0+16.640 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 = -0.41 (-0.13,+0.15),
the high energy photon index beta = -2.75 (-0.25,+0.18),
the peak energy Ep = 155 (-9,+9) keV,
chi2 = 89/97 dof.
Assuming the redshift z=5.26 (Thakur et al., GCN 41160)
and a standard cosmology with H_0 = 67.3 km/s/Mpc, Omega_M = 0.315,
and Omega_Lambda = 0.685 (Planck Collaboration, 2014),
we estimate the burst isotropic energy release E_iso to (5.85 ± 0.49)x10^53 erg,
the isotropic peak luminosity L_iso to (1.30 ± 0.13)x10^54 erg/s, and
the rest-frame peak spectral energy Ep,z to (970 ± 56) keV.
With the obtained estimates, GRB 250725A is consistent with 68% prediction bands
of both 'Amati' and 'Yonetoku' relations for the sample of >300 long KW GRBs
with known redshifts (Tsvetkova et al., 2017; Tsvetkova et al., 2021),
see http://www.ioffe.ru/LEA/GRBs/GRB250725_T06698/GRB250725A_rest_frame.pdf
All the quoted errors are estimated at the 68% confidence level.
All the presented results are preliminary.