GCN Circular 31959
Subject
Konus-Wind detection of GRB 220426A
Event
Date
2022-04-27T20:15:34Z (4 years ago)
From
Dmitry Frederiks at Ioffe Institute <fred@mail.ioffe.ru>
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 220426A (BALROG localization: Biltzinger et al., GCN Circ.
31950;
Swift/BAT-GUANO detection outside the coded FOV: Tohuvavohu et al.,
GCN Circ. 31954;
Fermi-GBM detection: Malacaria & Meegan, GCN Circ. 31955;
IPN localization: Kozyrev et al., GCN 31958)
triggered Konus-Wind (KW) at T0=24589.598 s UT (06:49:49.598).
The burst light curve shows a bright, double-peaked pulse
which starts at ~T0-0.5 s and has a total duration of ~11 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/GRB220426_T24589/
As observed by Konus-Wind, the burst had
a fluence of (9.2 �� 0.2)x10^-5 erg/cm^2 and
a 64-ms peak energy flux, measured from T0 + 2.432 s,
of (2.9 �� 0.2)x10^-5 erg/cm^2/s (both in the 20 keV - 10 MeV energy range).
The time-integrated spectrum (measured from T0 to T0+13.312 s)
is best fit in the 20 keV - 15 MeV range
by the GRB (Band) function with the following model parameters:
the low-energy photon index alpha = -0.29 (-0.07,+0.07),
the high energy photon index beta = -4.00 (-0.71,+0.32),
the peak energy Ep = 158 (-3,+4) keV,
chi2 = 112/97 dof.
The spectrum near the peak count rate (measured from T0+2.304 s
to T0+2.560 s) is best fit in the 20 keV - 15 MeV range
by the GRB (Band) function with the following model parameters:
the low-energy photon index alpha = 0.10 (-0.17,+0.21),
the high energy photon index beta = -5.6 (-4.3,+1.7),
the peak energy Ep = 227 (-15,+13) keV,
chi2 = 47/38 dof.
All the quoted errors are estimated at the 90% confidence level.
All the presented results are preliminary.