TITLE:   GCN CIRCULAR
NUMBER:  45718
SUBJECT: GRB 260924A: NOT optical counterpart confirmation
DATE:    26/09/24 07:35:16 GMT
FROM:    Daniele Bjørn Malesani at Cosmic Dawn Center, Niels Bohr Institute <daniele.malesani@nbi.ku.dk>

L. Izzo (INAF/OACN and DARK/NBI), J. An (NAOC), A. Saccardi (CEA/Irfu), G. Corcoran (UCD), S.Y. Fu (HUST), D. Xu (NAOC), D. B. Malesani (DAWN/NBI), A. S. Mårtensson (NOT), report on behalf of a larger collaboration:

We observed the field of the Swift/BAT GRB 260924A (D'Elia et al., GCN 45713) using the Nordic Optical Telescope (NOT) equipped with the ALFOSC instrument. The target had only a short visibility window from La Palma. Observations started at 05:38:57 UT on September 24 2026 (about 4.43 hr after the Swift trigger), and consisted of 3x300 s in the SDSS-r and 5x200 s in the SDSS-z band. 

Within the enhanced Swift/XRT localisation region reported by Evans et al. (GCN 45715), we detect the source first noted by Hu et al. (GCN 45717), for which we report the following coordinates:

RA (J2000) = 08:55:03.10
Dec (J2000) = +12:02:35.42

with an estimated error of ~0.5".

In our stacked images we measure the following AB magnitudes:

r = 16.28 +/- 0.02
z = 16.00 +/- 0.02

These magnitudes are calibrated using nearby objects from the Pan-STARRS catalog and are not corrected for Galactic extinction.