GCN Circular 35751

D. Svinkin, D. Frederiks,  A. Lysenko, A. Ridnaia,
and T. Cline on behalf of the Konus-Wind team,

A. Goldstein, M. S. Briggs, C. Wilson-Hodge,
and E. Burns on behalf of the Fermi GBM team,

and

S. Barthelmy, J. Cummings, H. Krimm, D. Palmer, and A. Tohuvavohu
on behalf of the Swift-BAT team,

report:

The long-duration GRB 240209A
(Fermi-GBM detection: The Fermi GBM team, GCN 35712
Not found
 
 
;
Malacaria et al., GCN 35729
Not found
 
 
)
was detected by Fermi (GBM trigger 729152364) and
Konus-Wind, in the waiting mode, at about 22760 s UT (06:19:20).

We have triangulated it to a Konus-GBM annulus centered at
RA(2000)=119.672 deg (07h 58m 41s) Dec(2000)=+19.090 deg (+19d 05' 25"),
whose radius is 66.074 +/- 14.729 deg (3 sigma).

The annulus combined with the Fermi-GBM final position (GCN 35712
Not found
 
 
;
glg_healpix_all_bn240209263_v01) gives ~2019 sq. deg (3 sigma) localization region.

The reported optical counterpart candidate GOTO24pw/AT2024cew
Not found
 
 

(Belkin et al., GCN 35715
Not found
 
 
) is outside the Konus-GBM annulus,
implying that the optical transient is unrelated to the GRB.

A triangulation map and HEALPix FITS file are posted at
http://www.ioffe.ru/LEA/GRBs/GRB240209_T22759/IPN