TITLE:   GCN CIRCULAR
NUMBER:  43389
SUBJECT: Konus-Wind detection of GRB 260101A
DATE:    26/01/13 15:31:48 GMT
FROM:    Dmitry Svinkin at Ioffe Institute <svinkin@mail.ioffe.ru>

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

The long-duration GRB 260101A
(Fermi-GBM detection: The Fermi GBM team, GCN 43284;
Hristov and Meegan, GCN 43297;
Swift-BAT detection: Cenko et al., GCN 43285;
Markwardt et al., GCN 43354;
SVOM-GRM detection: Yu et al., GCN 43292;
GECAM-B detection: Wang et al., GCN 43294)
triggered Konus-Wind at T0=3419.619 s UT (00:56:59.619).

The burst light curve shows a multipeaked structure
which starts at ~T0-26 s and has a total duration of ~30 s.
The emission is seen up to ~1 MeV.

The Konus-Wind light curve of this GRB is available at
http://www.ioffe.ru/LEA/GRBs/GRB260101_T03419/

As observed by Konus-Wind, the burst
had the total fluence of 7.47(-0.65,+0.77)x10^-6 erg/cm2,
and the 64-ms peak flux, measured from T0+0.210 s,
of 1.95(-0.42,+0.44)x10^-6 erg/cm2/s
(both in the 20 keV - 10 MeV energy range).

Since the main fraction of burst counts 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 T0-26.365 s to T0+3.168 s)
by a power law with exponential cutoff (CPL) model:
dN/dE ~ (E^alpha)*exp(-E*(2+alpha)/Ep),
yields alpha = -1.50(-0.11,+0.13) and Ep = 176(-30,+45) keV.

Modelling the KW 3-channel spectrum near the maximum count rate
(measured from T0-5.757 s to T0+3.168 s)
by the CPL model yields
alpha = -1.44(-0.15,+0.20) and Ep = 129(-18,+25) keV.

Assuming the redshift z=2.623 (de Ugarte Postigo et al., GCN 43287)
and a standard cosmology with H_0 = 67.3 km/s/Mpc, Omega_M = 0.315,
and Omega_Lambda = 0.685 (Planck Collaboration, 2014),
we estimate the following rest-frame parameters:
the isotropic energy release E_iso is 1.21(-0.11,+0.12)x10^53 erg,
the peak luminosity L_iso is 1.15(-0.25,+0.26)x10^53 erg/s,
the rest-frame peak energy of the time-averaged spectrum
Ep,i,z is 637(-109,+162) keV and the spectrum near the maximum count rate 
Ep,p,z is 467(-65,+90) keV.

With the obtained estimates, GRB 260101A is inside 68% prediction bands for both 
the 'Amati' and the 'Yonetoku' relations derived for the sample of >300 long KW GRBs with 
known redshifts (Tsvetkova et al., 2017; Tsvetkova et al., 2021),
see http://www.ioffe.ru/LEA/GRBs/GRB260101_T03419/GRB260101A_rest_frame.pdf

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