GCN Circular 39205
Subject
Konus-Wind detection of GRB 250204B
Date
2025-02-07T15:46:33Z (3 months ago)
From
Anna Ridnaia at Ioffe Institute <ridnaia@mail.ioffe.ru>
Via
Web form
A. Ridnaia, D. Frederiks, A. Lysenko, D. Svinkin,
A. Tsvetkova, M. Ulanov, and T. Cline,
on behalf of the Konus-Wind team, report:
The short-duration GRB 250204B
(Fermi-GBM detection: Fermi GBM team, GCN 39141;
AstroSat CZTI detection: Dasgupta et al., GCN 39142;
IPN triangulation: Svinkin et al., GCN 39145;
SVOM/GRM observation: Zhang et al., GCN 39163)
triggered Konus-Wind at T0=24073.659 s UT (06:41:13.659).
The burst light curve shows a single pulse
which starts at ~T0-0.1 s and has a total duration of ~1.5 s.
The emission is seen up to ~2 MeV.
The Konus-Wind light curve of this GRB is available at
http://www.ioffe.ru/LEA/GRBs/GRB250204_T24073/
As observed by Konus-Wind, the burst
had a fluence of 2.99(-0.29,+0.37)x10^-6 erg/cm2,
and a 16-ms peak flux, measured from T0+0.008 s,
of 7.51(-1.64,+1.74)x10^-6 erg/cm2/s
(both in the 20 keV - 10 MeV energy range).
The time-averaged spectrum of the burst
(measured from T0 to T0+0.256 s)
is best fit in the 20 keV - 10 MeV range
by a power law with exponential cutoff model:
dN/dE ~ (E^alpha)*exp(-E*(2+alpha)/Ep)
with alpha = -0.85(-0.17,+0.19)
and Ep = 383(-66,+92) keV (chi2 = 16/22 dof).
Fitting by a GRB (Band) model yields the same alpha and Ep,
and an upper limit on the high energy photon index: beta < -2.1
(chi2 = 16/21 dof).
All the quoted errors are at the 68% confidence level.
All the quoted values are preliminary.