TITLE:   GCN CIRCULAR
NUMBER:  22640
SUBJECT: Konus-Wind observation of GRB 180411A
DATE:    18/04/12 12:00:31 GMT
FROM:    Dmitry Frederiks at Ioffe Institute  <fred@mail.ioffe.ru>

D. Frederiks, S. Golenetskii, R.Aptekar, M. Ulanov, D. Svinkin,
A. Tsvetkova, A.Lysenko, A. Kozlova, and T. Cline,
on behalf of the Konus-Wind team, report:

The long GRB 180411A (Swift/BAT detection: Liu et al., GCN 22630;
Markwardt et al., GCN 22633; Fermi-GBM detection: Poolakkil, GCN 22634)
triggered Konus-Wind at T0=44862.530 s UT (12:27:42.530).

The KW light curve shows two multipeaked pulses with
a total duration of ~90 s.
The emission is seen up to ~10 MeV.

As observed by Konus-Wind, the burst had a fluence of
(4.01 ± 0.91)x10^-5 erg/cm2 and a 64-ms peak energy flux,
measured from T0+50.496, of (3.3 ± 0.7)x10^-6 erg/cm2
(both in the 20 keV - 10 MeV energy range).

The time-integrated spectrum (measured from T0 to T0+82.368 s)
is best fit in the 20 keV - 15 MeV range by by the GRB (Band)
function with the following model parameters:
the low-energy photon index alpha = -1.17 (-0.12,+0.15),
the high energy photon index beta = -2.39 (-0.90,+0.31),
the peak energy Ep = 239 (-49,+55) keV,
chi2 = 90/97 dof.

The spectrum near the peak count rate (measured from T0+41.408
to T0+57.792 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 = -0.89 (-0.13,+0.16),
the high energy photon index beta = -2.49 (-0.77,+0.31),
the peak energy Ep = 255 (-40,+44) keV,
chi2 = 96/97 dof.

The Konus-Wind light curve of this GRB is available at
http://www.ioffe.ru/LEA/GRBs/GRB180411_T44862/

All the quoted errors are estimated at the 90% confidence level.
All the presented results are preliminary.