GCN Circular 22743

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 180523A
(IPN Triangulation: Hurley et al., GCN Circ. 22740
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triggered Konus-Wind at T0=66028.802 s UT (18:20:28.802).

The burst light curve shows a bright main pulse lasting about 35 s,
which is followed by a fainter second episode which
started at ~T0+87.4 s and lasted up to ~T0+87.9 s.
The emission in the main pulse is seen up to ~2 MeV.

As observed by Konus-Wind, the burst
had a fluence of 1.06(-0.08,+0.08)x10^-4 erg/cm2,
and a 64-ms peak flux, measured from T0+12.368 s,
of 1.11(-0.22,+0.22)x10^-5 erg/cm2/s
(both in the 20 keV - 10 MeV energy range).

The time-averaged spectrum of the main episode
(measured from T0 to T0+36.608 s)
is best fit in the 20 keV - 2 MeV range
by the GRB (Band) model with the following parameters:
the low-energy photon index alpha = -0.69(-0.06,+0.07),
the high energy photon index beta = -2.68(-0.30,+0.19),
the peak energy Ep = 307(-17,+18) keV
(chi2 = 49/61 dof).

The spectrum near the maximum count rate
(measured from T0+12.288 to T0+14.080 s)
is best fit in the 20 keV - 2 MeV range
by the GRB (Band) model with the following parameters:
the low-energy photon index alpha = -0.51(-0.14,+0.16),
the high energy photon index beta = -2.66(-0.89,+0.29),
the peak energy Ep = 325(-39,+49) keV
(chi2 = 53/55 dof).

The Konus-Wind light curve of this GRB is available at
http://www.ioffe.ru/LEA/GRBs/GRB180523_T66028/

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