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GCN Circular 27577

Subject
Konus-Wind observation of GRB 200412A
Date
2020-04-14T15:38:35Z (4 years ago)
From
Anna Ridnaia at Ioffe Institute <ridnaia@mail.ioffe.ru>
A. Ridnaia, S. Golenetskii, R. Aptekar, D. Frederiks,
M. Ulanov, D. Svinkin, A. Tsvetkova, A. Lysenko, and T. Cline
on behalf of the Konus-Wind team, report:

The long-duration GRB 200412A
(BALROG localization: Kunzweiler et al., GCN Circ. 27546;
Fermi-GBM detection: Mailyan and Hamburg., GCN Circ. 27550;
IPN triangulation: Hurley et al., GCN Circ. 27560)
triggered Konus-Wind at T0=25034.8 s UT (06:57:14.800).

The burst light curve shows a multipeaked structure
which starts at ~T0-0.2 s and has a total duration of ~13.3 s.
The emission is seen up to ~4 MeV.

As observed by Konus-Wind, the burst
had a fluence of 3.27(-0.32,+0.35)x10^-5 erg/cm2,
and a 64-ms peak flux, measured from T0+3.792 s,
of 1.18(-0.15,+0.15)x10^-5 erg/cm2/s
(both in the 20 keV - 10 MeV energy range).

The time-averaged spectrum of the burst
(measured from T0 to T0+13.056 s)
is best fit in the 20 keV - 4 MeV range
by the GRB (Band) model with the following parameters:
the low-energy photon index alpha = -0.59(-0.11,+0.12),
the high energy photon index beta = -2.68(-0.41,+0.23),
the peak energy Ep = 229(-19,+20) keV
(chi2 = 56/68 dof).

The spectrum near the maximum count rate
(measured from T0+0.256 to T0+4.864 s)
is best fit in the 20 keV - 4 MeV range
by a power law with exponential cutoff model:
dN/dE ~ (E^alpha)*exp(-E*(2+alpha)/Ep)
with  alpha = -0.69(-0.08,+0.09)
and Ep = 275(-16,+18) keV (chi2 = 47/68 dof).
Fitting by a GRB (Band) model yields the same alpha and Ep,
and an upper limit on the high energy photon index: beta < -2.8
(chi2 = 46/67 dof).

The Konus-Wind light curve of this GRB is available at
http://www.ioffe.ru/LEA/GRBs/GRB200412_T25034/

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