TITLE:   GCN CIRCULAR
NUMBER:  43592
SUBJECT: Konus-Wind detection of GRB 260128A / EP260128a
DATE:    26/02/01 16:47:41 GMT
FROM:    Dmitry Frederiks at Ioffe Institute <fred@mail.ioffe.ru>

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-duration GRB 260128A/EP260128a
(Einstein Probe detection: Zhow et al., GCN 43549;
Fermi-GBM Sub-Threshold Detection: Ravasio et al., GCN 43556)
was detected by Konus-Wind (KW) in the waiting mode
at T0=T0(KW)~23:40:00 UTC.

A Bayesian block analysis of the KW data in the 20-1500 keV
band reveals a >10 sigma count rate increase in the interval
from ~T0-101 s to ~T0+61 s.

The Konus-Wind light curve of this GRB is available at
http://www.ioffe.ru/LEA/GRBs/GRB260128A/

The time-integrated spectrum of the burst (measured from from
~T0-101 s to ~T0+61 s) is best described in the 20 - 1500 keV
range by a power law with exponential cutoff (CPL) model
with alpha = -0.93 ± 0.99 and Ep = (103 ± 16) keV.

The spectrum near the peak count rate (measured from ~T0-4 s to T0+14 s)
is best described by a CPL model with alpha = -1.26 ± 0.30 and Ep = (178 ± 31) keV.

The total burst fluence is (6.12 ± 2.89)x10^-6 erg/cm^2,
and the 2.944 s peak energy flux, measured from T0+2.082 s,
is (1.57 ± 0.44)x10^-7 erg/cm^2 (both in the 20 - 1500 keV energy range).

All the quoted errors are estimated at the 68% confidence level.
All the presented results are preliminary.