TITLE:   GCN CIRCULAR
NUMBER:  38968
SUBJECT: Konus-Wind detection of GRB 250116A
DATE:    25/01/17 13:56:46 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, bright GRB 250116A
(Fermi/GBM detection: Bissaldi et al., GCN 38962;
Fermi/LAT detection: Holzmann Airasca et al., GCN 38963;
INTEGRAL/SPI-ACS and PICsIT detection: Barria et al., GCN 38965;
GECAM-B detection: Wang et al., GCN 38967)
triggered Konus-Wind at T0=45234.821 s UT (12:33:54.821).

The burst light curve shows a bright initial 
multipeaked emission episode which starts at ~T0-0.3 s and 
has a total duration of ~24.2 s, followed by a weaker
emission traced up to ~175 s.
The emission is seen up to ~3 MeV.

The Konus-Wind light curve of this GRB is available at
http://www.ioffe.ru/LEA/GRBs/GRB250116_T45234/

As observed by Konus-Wind, the initial emission episode
had a fluence of 1.05(-0.03,+0.03)x10^-4 erg/cm2,
and a 64-ms peak flux, measured from T0+15.344 s,
of 1.77(-0.14,+0.14)x10^-5 erg/cm2/s
(both in the 20 keV - 10 MeV energy range).

The time-averaged spectrum of the initial episode
(measured from T0 to T0+26.112 s)
is best fit in the 20 keV - 10 MeV range
by the GRB (Band) model with the following parameters:
the low-energy photon index alpha = -0.58(-0.04,+0.04),
the high energy photon index beta = -3.21(-0.28,+0.18),
the peak energy Ep = 382(-10,+11) keV
(chi2 = 111/98 dof).

A spectrum of the weaker emission tail
(measured from T0+26.112 to T0+181.760 s)
is best fit by a simple power-law (PL) function with
the PL index of -2.13(-0.17,+0.19), chi2 = 97/100 dof.
A 20 keV - 10 MeV fluence in this interval is estimated
to 1.25(-0.29,+0.39)x10^-5 erg/cm2.

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