TITLE:   GCN CIRCULAR
NUMBER:  38526
SUBJECT: Konus-Wind detection of GRB 241209D
DATE:    24/12/10 14:55:58 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 241209D
(Fermi-GBM detection: Fermi GBM team, GCN 38488;
Malacaria & Meegan, GCN 38507;
Swift-BAT detection: Parsotan et al., GCN 38489;
AstroSat CZTI detection: Tembhurnikar et al., GCN 38518)
was detected by Konus-Wind (KW) in the waiting mode.

A Bayesian block analysis of the KW waiting mode data in the 20-300 keV band
reveals a >13 sigma count rate increase in the interval
from T0-2.0 s to T0+42.160 s where T0 = T0(BAT) = 10:59:45.649 UT.

The KW light curve of this burst is available at
http://www.ioffe.ru/LEA/GRBs/GRB241209D/

Modeling a time-integrated spectrum of the burst
(from T0-2.0 s to T0+42.160 s)
by a power law with exponential cutoff (CPL) model
dN/dE ~ (E^alpha)*exp(-E*(2+alpha)/Ep):
yields alpha = -1.16 (-0.37, +4.03) and Ep = 90(-12,+14) keV.

The total burst fluence is 8.79(-0.87,+1.74)x10^-6 erg/cm^2,
and the 2.944 s peak energy flux, measured from T0-2.0 s,
is 5.86(-0.75,+1.25)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.