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GCN Circular 35714

Subject
Konus-Wind detection of GRB 240204A
Date
2024-02-11T19:46:09Z (18 days ago)
From
Dmitry Svinkin at Ioffe Institute <svinkin@mail.ioffe.ru>
Via
legacy email
D. Svinkin, D. Frederiks, M. Ulanov, A. Tsvetkova,
A. Lysenko, A. Ridnaia, and T. Cline
on behalf of the Konus-Wind team, report:

The long-duration GRB 240204A
(Fermi-GBM detection: The Fermi GBM team, GCN 35664;
Swift-BAt detection: Cenko et al., GCN 35666;
AstroSat-CZTI detection: Joshi et al., GCN 35692)
triggered Konus-Wind at T0=54473.519 s UT (15:07:53.519).

The burst light curve shows a single pulse
which starts at ~T0-4.5 s and has a total duration of ~21.5 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/GRB240204_T54473/

As observed by Konus-Wind, the burst
had a fluence of 1.37(-0.07,+0.07)x10^-5 erg/cm2,
and a 64-ms peak flux, measured from T0+2.448 s,
of 4.22(-1.15,+1.15)x10^-6 erg/cm2/s
(both in the 20 keV - 10 MeV energy range).

The time-averaged spectrum of the burst
(measured from T0 to T0+8.448 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 = -1.29(-0.16,+0.17)
and Ep = 81(-6,+6) keV (chi2 = 87/83 dof).
Fitting by a GRB (Band) model yields the same alpha and Ep,
and an upper limit on the high energy photon index: beta < -2.9
(chi2 = 86/82 dof).

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


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