TITLE:   GCN CIRCULAR
NUMBER:  43517
SUBJECT: Konus-Wind detection of GRB 260120B
DATE:    26/01/26 13:06:35 GMT
FROM:    Anna Ridnaia at Ioffe Institute <ridnaia@mail.ioffe.ru>

A. Ridnaia, D. Frederiks, A. Lysenko, D. Svinkin,
A. Tsvetkova,  M. Ulanov, and T. Cline,
on behalf of the Konus-Wind team, report:

The long-duration GRB 260120B
(Fermi GBM detection: Fermi GBM team, GCN 43477;
Godwin & Meegan, GCN 43489;
Swift-BAT detection: Ferro et al., GCN 43479;
Palmer et al., GCN 43493;
AstroSat CZTI detection: Goyal et al., GCN 43504)
triggered Konus-Wind at T0=64826.649 s UT (18:00:26.649).

The burst light curve shows a single pulse,
which starts at ~T0-3.2 s and has a total duration of ~5.9 s.

The Konus-Wind light curve of this GRB is available at
http://www.ioffe.ru/LEA/GRBs/GRB260120_T64826/

As observed by Konus-Wind, the burst
had a fluence of 3.41(-0.52,+0.58)x10^-6 erg/cm2,
and a 64-ms peak flux, measured from T0-0.064 s,
of 1.97(-0.58,+0.60)x10^-6 erg/cm2/s
(both in the 20 keV - 10 MeV energy range).

Since a major part of the burst emission was 
detected before the trigger, the spectral analysis
was performed using the KW 3-channel light curve data.

Modelling the KW 3-channel time-integrated spectrum
(measured from T0-3.173 s to T0+2.720 s)
by a power law with exponential cutoff (CPL) model:
dN/dE ~ (E^alpha)*exp(-E*(2+alpha)/Ep),
yields alpha = -0.56(-0.23,+0.30) and Ep = 246(-53,+67) keV.

All the quoted errors are at the 68% confidence level.
All the quoted values are preliminary.