TITLE:   GCN CIRCULAR
NUMBER:  36646
SUBJECT: Konus-Wind detection of GRB 240606B
DATE:    24/06/08 09:47:59 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 240606B
(Swift/BAT-GUANO arcminute localization: DeLaunay et al., GCN 36628;
GECAM-B detection: Wang et al., GCN 36633;
Fermi-GBM detection: Bala & Meegan, GCN 36640)
triggered Konus-Wind at T0=48787.583 s UT (13:33:07.583).

The burst light curve shows a multipeaked structure
which starts at ~T0-53.0 s and has a total duration of ~58.4 s.
The emission is seen up to ~4 MeV.

The Konus-Wind light curve of this GRB is available at
http://www.ioffe.ru/LEA/GRBs/GRB240606_T48787/

As observed by Konus-Wind, the burst
had a fluence of 5.07(-0.10,+1.54)x10^-6 erg/cm2,
and a 64-ms peak flux, measured from T0+0.318 s,
of 1.68(-0.34,+0.61)x10^-6 erg/cm2/s
(both in the 20 keV - 10 MeV energy range).

Since the bulk of the burst emission was detected before
the trigger, the spectral analysis was performed using
the KW 3-channel light curve data.

Modelling the KW 3-channel time-integrated spectrum
(measured from T0-53.014 s to T0+5.360 s)
by a power law with exponential cutoff (CPL) model,
dN/dE ~ (E^alpha)*exp(-E*(2+alpha)/Ep),
yields alpha = -0.55(-0.83,+3.21) and Ep = 116(-21,+62) keV.

A CPL fit to the spectrum near the peak count rate,
measured from T0-0.400 s to T0+0.816 s, gives
alpha -1.20(-0.14,+0.14), and Ep = 475(-128,+239) keV.

All the quoted errors are at the 68% confidence level.
All the quoted values are preliminary.