GCN Circular 43712
Subject
Konus-Wind detection of GRB 260207B
Event
Date
2026-02-12T14:06:38Z (a day ago)
From
Dmitry Svinkin at Ioffe Institute <svinkin@mail.ioffe.ru>
Via
Web form
D. Svinkin, D. Frederiks, A. Lysenko, A. Ridnaia,
A. Tsvetkova, M. Ulanov, and T. Cline
on behalf of the Konus-Wind team, report:
The short-duration GRB with extended emission (EE) GRB 260207B
(Fermi-GBM detection: Fermi GBM team, GCN 43629;
Sonawane & Bala, GCN 43634;
GECAM-B detection: Zao et al., GCN 43644;
AstroSat-CZTI detection: Goyal et al., GCN 43680;
IPN triangulation: Kozyrev et al., GCN 43691;
GRID detection: Zeng et al., GCN 43710)
triggered Konus-Wind at T0=47529.467 s UT (13:12:09.467).
The burst light curve shows a short initial pulse,
which starts at ~T0-40 ms and has a duration of ~220 ms.
The initial pulse is followed by a weaker extended emission (EE),
starting at ~T0+9 s, peaking at ~T0+43 s, and lasting up to ~T0+95 s.
The emission in the initial pulse is seen up to ~2 MeV.
The Konus-Wind light curve of this GRB is available at
http://www.ioffe.ru/LEA/GRBs/GRB260207_T47529/
As observed by Konus-Wind, the initial pulse
had the fluence of 2.66(-0.19,+0.20)x10^-6 erg/cm2,
and the 16-ms peak flux, measured from T0+0.104 s,
of 4.41(-0.54,+0.58)x10^-5 erg/cm2/s
(both in the 20 keV - 10 MeV energy range).
The time-averaged spectrum of the initial pulse
(measured from T0 to T0+0.192 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 = -0.99(-0.08,+0.08)
and Ep = 495(-60,+72) keV (chi2 = 44/43 dof).
Fitting by a GRB (Band) model yields the same alpha and Ep,
and an upper limit on the high energy photon index: beta < -3.1
(chi2 = 44/42 dof).
The time-averaged spectrum of the EE
(measured from T0+8.448 s to T0+73.984 s)
is best fit in the 20 keV - 10 MeV range
by a power law with exponential cutoff model:
with alpha = -1.67(-0.21,+0.24)
and Ep = 44 (-19,+11) keV (chi2 = 93/98 dof).
Fitting by a GRB (Band) model yields the same alpha and Ep,
and an upper limit on the high energy photon index: beta < -3.0
(chi2 = 93/97 dof).
From this spectrum, the total EE fluence is 5.02(-0.4,+0.4)x10^-6 erg/cm2,
a factor of ~2 higher than that of the initial pulse.
All the quoted errors are at the 68% confidence level.
All the quoted values are preliminary.