GCN Circular 40107
Subject
Konus-Wind detection of GRB 250406B (short/hard)
Date
2025-04-07T17:14:04Z (19 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 bright, short-duration GRB 250406B
(IPN localization: Kozyrev et al., GCN 40106).
triggered Konus-Wind (KW) at T0=21401.479 s UT (05:56:41.479).
The burst light curve shows a multi-peaked pulse,
which starts at ~T0-0.032 s and has a duration of ~0.240 s.
The emission is seen up to ~10 MeV.
The Konus-Wind light curve of this GRB is available at
http://www.ioffe.ru/LEA/GRBs/GRB250406_T21401/
As observed by Konus-Wind, the burst had the total fluence
of 2.54(-0.51,+0.62)x10^-6 erg/cm^2 and a 16-ms peak energy flux,
measured from T0-0.016 s, of 3.06(-0.61,+0.69)x10^-5 erg/cm^2/s
(both in the 20 keV - 10 MeV energy range).
The time-integrated spectrum of the burst (measured from T0 to T0+0.256 s)
is best fit in the 20 keV - 15 MeV range by a power law with exponential
cutoff (CPL) model: dN/dE ~ (E^alpha)*exp(-E*(2+alpha)/Ep)
with alpha = -0.97(-0.10,+0.12) and Ep = 2118(-590,+818) keV (chi2 = 35/38 dof).
Fitting this spectrum by a Band function yields the same values of alpha and Ep,
and an upper limit on the high energy photon index beta of -2.15 (chi2 = 35/37 dof).
All the quoted errors are estimated at the 68% confidence level.
All the presented results are preliminary.