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GCN Circular 33586

Subject
Konus-Wind detection of GRB 230405B
Date
2023-04-07T11:34:01Z (a year ago)
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 GRB 230405B
(Fermi-GBM detection: The Fermi GBM team, GCN 33570;
Wood & Meegan, GCN 33583;
Swift-BAT detection: Page et al., GCN 33571;
AstroSat CZTI detection: Navaneeth et al., GCN 33575;
AGILE detection: Casentini et al., GCN 33585)
triggered Konus-Wind at T0=71884.77 s UT (19:58:04.770).

The burst light curve shows a single pulse,
which starts at ~T0-6.1 s and has a total duration of ~10.7 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/GRB230405_T71884/

As observed by Konus-Wind, the burst
had a fluence of 2.24(-0.23,+0.27)x10^-5 erg/cm2,
and a 64-ms peak flux, measured from T0+1.088 s,
of 9.76(-1.97,+2.26)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 the GRB (Band) model with the following parameters:
the low-energy photon index alpha = -0.37(-0.26,+0.30),
the high energy photon index beta = -2.75(-0.64,+0.31),
the peak energy Ep = 184(-20,+23) keV
(chi2 = 101/91 dof).

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