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GCN Circular 35874

Subject
Konus-Wind detection of GRB 240227A (short/hard)
Date
2024-03-05T16:30:28Z (a month ago)
From
Dmitry Frederiks at Ioffe Institute <fred@mail.ioffe.ru>
Via
legacy email
D. Frederiks, A.Lysenko, A. Ridnaia, D. Svinkin,
A. Tsvetkova,  M. Ulanov, and T. Cline,
on behalf of the Konus-Wind team, report:

The short GRB 240227A (Fermi-GBM detection: The Fermi GBM team, GCN 35814;
IPN triangulation: Svinkin et al., GCN 35821; Kozyrev et al., GCN 35871).
triggered Konus-Wind (KW) at T0=16812.986 s UT (04:40:12.986).

The burst light curve shows a single multi-peaked emission pulse
which starts at ~T0-0.400 s and has a duration of ~0.5 s.
The emission is seen up to ~2 MeV.

The Konus-Wind light curve of this GRB is available at
http://www.ioffe.ru/LEA/GRBs/GRB240227_T16812/

As observed by Konus-Wind, the burst had
the total fluence of 1.72(-0.28,+0.36)x10^-6 erg/cm^2
and a 16-ms peak energy flux, measured from T0+0.032 s,
of 8.21(-2.63,+3.09)x10^-6 erg/cm^2/s (both in the 20 keV - 10 MeV energy range).

Since a major part of the burst emission was detected before the trigger,
a time-averaged spectral analysis was performed using the KW 3-channel light curve data.
Modeling the 3-channel time-integrated spectrum (measured from T0-0.400 s to T0+0.096 s)
by a power law with exponential cutoff (CPL) model dN/dE ~ (E^alpha)*exp(-E*(2+alpha)/Ep)
yields alpha = -0.47 (-0.24, + 0.28) and Ep = 688(-133,+222) keV.

A multi-channel spectrum near the peak count rate (measured from T0 to T0+0.064 s)
is best fit in the 20 keV - 15 MeV range by a CPL model
with  alpha = -0.12(-0.47,+0.70) and Ep = 759(-233,+403) keV (chi2 = 6.4/10 dof).


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


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