TITLE:   GCN CIRCULAR
NUMBER:  30077
SUBJECT: Konus-Wind detection of GRB 210524A
DATE:    21/05/25 16:04:23 GMT
FROM:    Dmitry Svinkin at Ioffe Institute  <svinkin@mail.ioffe.ru>

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

The long-duration GRB 210524A
(Fermi-GBM detection: The Fermi GBM team, GCN Circ. 30071;
IPN triangulation: Hurley et al., GCN Circ. 30076)
triggered Konus-Wind at T0=18010.925 s UT (05:00:10.925).

The burst light curve shows a multi-peaked structure
which starts at ~T0-3.5 s and has a total duration of ~11.5 s.
The emission is seen up to ~1 MeV.

The Konus-Wind light curve of this GRB is available at
http://www.ioffe.ru/LEA/GRBs/GRB210524_T18010/

As observed by Konus-Wind, the burst
had a fluence of 8.64(-0.52,+0.56)x10^-6 erg/cm2,
and a 64-ms peak flux, measured from T0+2.752 s,
of 3.76(-1.00,+1.00)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 - 2 MeV range
by a power law with exponential cutoff model:
dN/dE ~ (E^alpha)*exp(-E*(2+alpha)/Ep)
with  alpha = -1.33(-0.19,+0.20)
and Ep = 99(-10,+11) keV (chi2 = 45/56 dof).
Fitting by a GRB (Band) model yields the same alpha and Ep,
and an upper limit on the high energy photon index: beta < -2.7
(chi2 = 45/55 dof).

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