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GCN Circular 24534

Subject
Konus-Wind observation of GRB 190511A
Date
2019-05-14T10:00:01Z (5 years ago)
From
Anna Kozlova at Ioffe Institute <ann_kozlova@mail.ioffe.ru>
A. Kozlova, 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 190511A
(Swift-BAT detection: Bernardini et al., GCN Circ. 24472,
Barthelmy et al., GCN Circ. 24502;
Fermi-GBM observation: Kienlin et al., GCN Circ. 24482;
Fermi-LAT detection: Axelsson et al., GCN Circ. 24483)
triggered Konus-Wind at T0=26067.524 s UT (07:14:27.524).

The burst light curve shows a multipeaked structure
which started at ~T0-2.6 s and had a total duration of ~31.8 s.
The emission is seen up to ~2 MeV.

As observed by Konus-Wind, the burst
had a fluence of 1.93(-0.11,+0.12)x10^-5 erg/cm2,
and a 64-ms peak flux, measured from T0+21.936 s,
of 3.81(-0.90,+0.91)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+33.024 s)
is best fit in the 20 keV - 2 MeV range
by a power law with exponential cutoff model:
dN/dE ~ (E^alpha)*exp(-E*(2+alpha)/Ep)
with  alpha = -0.69(-0.16,+0.17)
and Ep = 185(-15,+18) keV (chi2 = 49/58 dof).
Fitting by a GRB (Band) model yields the same alpha and Ep,
and an upper limit on the high energy photon index: beta < -2.4
(chi2 = 48/57 dof)

The spectrum near the maximum count rate
(measured from T0+16.640 to T0+24.832 s)
is best fit in the 20 keV - 2 MeV range
by a power law with exponential cutoff model
with  alpha = -0.52(-0.23,+0.26)
and Ep = 193(-20,+26) keV (chi2 = 53/58 dof).
Fitting by a GRB (Band) model yields the same alpha and Ep,
and an upper limit on the high energy photon index: beta < -3.0
(chi2 = 53/57 dof)

The Konus-Wind light curve of this GRB is available at
http://www.ioffe.ru/LEA/GRBs/GRB190511_T26067/

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