TITLE:   GCN CIRCULAR
NUMBER:  37130
SUBJECT: Konus-Wind detection of GRB 240807A (a counterpart of EP240807a)
DATE:    24/08/10 11:10:53 GMT
FROM:    Anna Ridnaia at Ioffe Institute <ridnaia@mail.ioffe.ru>

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

The long-duration GRB 240807A
(Fermi GBM detection: Fermi GBM team, GCN 37089;
SVOM-GRM detection: Wang et al., GCN 37111;
IPN triangulation: Ridnaia et al., GCN 37120)
was detected by Konus-Wind (KW) in the waiting mode
at T0~20568 s UT (05:42:48).

A Bayesian block analysis of the KW  waiting mode data
in the 20-300 keV band reveals a >8 sigma count rate
increase in the interval from ~T0+0.143 s to ~T0+3.087 s.

Corrected for the propagation time, the burst started ~4 s
before the start time of the fast X-ray transient EP240807a
(T0(EP)=05:42:48 UT; Fu et al., GCN 37088).
The positional (Ridnaia et al., GCN 37120) and temporal
coincidence of GRB 240807A with the EP transient supports
the conclusion that EP240807a is the GRB counterpart.

The Konus-Wind light curve of this GRB is available at
http://www.ioffe.ru/LEA/GRBs/GRB240807A/

The time-integrated spectrum of the burst,
measured from T0+0.143 s to T0+3.087 s,
cat be described by a power law with exponential cutoff (CPL) model
dN/dE ~ (E^alpha)*exp(-E*(2+alpha)/Ep)
with alpha = -0.60(-0.95,+3.74) and Ep = 134(-35,+285) keV.

The total burst fluence is 4.24(-0.01,+4.68)x10^-7 erg/cm^2,
and the 2.944 s peak energy flux, measured from T0+0.143 s,
is 1.43(-0.27,+1.61)x10^-7 erg/cm^2.
(both in the 20 keV - 10 MeV energy range).

All the quoted errors are estimated at the 68% confidence level.
All the presented results are preliminary.