TITLE: GCN CIRCULAR NUMBER: 40350 SUBJECT: GRB 250504A: REM optical/NIR observations DATE: 25/05/05 10:35:35 GMT FROM: Riccardo Brivio at INAF-OAB riccardo.brivio@inaf.it
R. Brivio, M. Ferro, P. D'Avanzo, S. Covino, D. Fugazza (INAF-OAB) report on behalf of the REM team:
We observed the field of GRB 250504A detected by Fermi/GBM (Fermi GBM team, GCN 40342) and Swift/BAT (Moss et al., GCN 40343) with the REM 60 cm robotic telescope located at the ESO observatory of La Silla (Chile). The observations were carried in the g, r, i, z, J, H, and K bands, started on 2025 May 05 at 01:09:20 UT (i.e. 1.7 hr after the burst), and lasted for about 1 hour.
From preliminary inspection, we do not detect any counterpart at the position of the optical afterglow (de Wet et al., GCN. 40347) down to the following 3sigma limits:
r > 19.3 (AB; calibrated against the SkyMapper catalogue), at a mid-time of 2.2 hours after the trigger;
H > 15.7 (Vega; calibrated against the 2MASS catalogue), at a mid-time of 2.1 hours after the trigger.
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