GCN Circular 35658

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

The short-duration GRB 240123C
(IPN triangulation: Ridnaia et al., GCN circ. 35627
Not found
 
 
;
AstroSat CZTI detection: Joshi et al., GCN circ. 35635
Not found
 
 
;
GRBAlpha detection: Dafcikova et al., GCN circ. 35643
Not found
 
 
)
triggered Konus-Wind at T0=83553.043 s UT (23:12:33.043).

The burst light curve shows a single-pulse structure
which starts at ~T0-0.1 s and has a total duration of ~1.0 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/GRB240123_T83553/

As observed by Konus-Wind, the burst
had a fluence of 2.91(-0.22,+0.23)x10^-6 erg/cm2,
and a 16-ms peak flux, measured from T0+0.160s,
of 1.17(-0.32,+0.33)x10^-5 erg/cm2/s
(both in the 20 keV - 10 MeV energy range).

A time-averaged spectrum of the burst
(measured from T0 to T0+0.256 s)
is best fit in the 20 keV - 10 MeV range
by a power law with exponential cutoff model:
dN/dE ~ (E^alpha)*exp(-E*(2+alpha)/Ep)
with alpha = 0.85(-0.40,+0.46)
and Ep = 210(-17,+19) keV (chi2 = 24/38 dof).
Fitting by a GRB (Band) model yields the close alpha and Ep,
and an upper limit on the high energy photon index: beta < -2.8
(chi2 = 22/37 dof).

All the quoted errors are at the 90% confidence level.
All the quoted values are preliminary.