TITLE:   GCN CIRCULAR
NUMBER:  36768
SUBJECT: Konus-Wind detection of GRB 240619A
DATE:    24/06/26 21:43:33 GMT
FROM:    Dmitry Svinkin at Ioffe Institute <svinkin@mail.ioffe.ru>

D. Svinkin, 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 240619A
(Fermi-GBM detection: The Fermi GBM team, GCN 36694;
CALET-CGBM detection: Torii et al., GCN 36719;
GRBAlpha detection: Dafcikova et al., GCN 36724;
GOTO OT detection: Gompertz et al., GCN 36715;
Swift-XRT afterglow detection: Capalbi et al., GCN 36721)
triggered Konus-Wind at T0=13408.204 s UT (03:43:28.204).

The burst light curve shows two separated emission episodes.
The initial harder episode starts at ~T0-0.2 s and has a total duration of ~14 s. The following softer episode starts at ~T0+22 s and ends at ~T0+36 s. The total burst duration is ~36 s.
The emission is seen up to ~10 MeV.

The Konus-Wind light curve of this GRB is available at
http://www.ioffe.ru/LEA/GRBs/GRB240619_T13408/

As observed by Konus-Wind, the burst
had a fluence of 1.35(-0.36,+0.79)x10^-5 erg/cm2,
and a 64-ms peak flux, measured from T0+0.052 s,
of 1.48(-0.50,+0.49)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+41.216 s)
is best fit in the 20 keV - 10 MeV range
by a power law with exponential cutoff model:
dN/dE ~ (E^alpha)*exp(-E*(2+alpha)/Ep)
with alpha = -1.62(-0.21,+0.32)
and Ep = 557(-300,+4475) keV (chi2 = 93/86 dof).
Fitting by a GRB (Band) model yields the same alpha and Ep,
and an upper limit on the high energy photon index: beta < -1.9
(chi2 = 93/85 dof).

The spectrum near the maximum count rate
(measured from T0 to T0+0.256 s)
is best fit in the 20 keV - 10 MeV range
by the GRB (Band) model with the following parameters:
the low-energy photon index alpha = -0.60(-0.52,+0.86),
the high energy photon index beta = -1.98(-8.02,+0.25),
the peak energy Ep = 480(-218,+870) keV
(chi2 = 29/40 dof).

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