GCN 43590: Konus-Wind detection of GRB 260131A/B

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 GRB 260131A/B (Fermi-GBM detection:
The Fermi GBM team, GCN 43579, Roberts, GCN 43585;
MAXI/GSC detection: Sugai et al., GCN 43580)
triggered Konus-Wind (KW) at T0=23972.646 s UT (06:39:32.646).

The burst consists of two separated emission pulses,
peaked around ~T0 and to T0+215 s, respectively.
The total duration of the burst is ~250 s.

The Konus-Wind light curve of this GRB is available at
http://www.ioffe.ru/LEA/GRBs/GRB260131_T23972/

As observed by Konus-Wind, the burst had
a fluence of (4.14 ± 0.91)x10^-5 erg/cm^2 and
a 64-ms peak energy flux, measured from T0 + 0.384 s,
of (4.33 ± 0.52)x10^-6 erg/cm^2/s (both in the 20 keV - 10 MeV energy range).

The time-integrated spectrum (measured from T0 to T0+238 s)
is best fit in the 20 keV - 15 MeV range by a GRB (Band) function
with the following model parameters:
the low-energy photon index alpha = -0.15 (-0.70,+1.61),
the high energy photon index beta = -1.97 (-0.20,+0.14),
the peak energy Ep = 124 (-40,+56) keV,
chi2 = 83/97 dof.

The spectrum near the peak count rate (measured from T0 to T0+8.448 s)
is best fit in the 20 keV - 15 MeV range by a GRB (Band) function
with the following model parameters:
the low-energy photon index alpha = -1.17 (-0.15,+0.17),
the high energy photon index beta = -1.98 (-0.18,+0.10),
the peak energy Ep = 300 (-68,+131) keV,
chi2 = 74/79 dof.

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