TITLE: GCN CIRCULAR NUMBER: 40452 SUBJECT: EP250512a/GRB 250512B: REM optical/NIR observations DATE: 25/05/13 10:28:43 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 EP250512a/GRB 250512B detected by EP/WXT (Zhao et al., GCN 40437) and SVOM/ECLAIRs (Maggi et al., GCN 40439) 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 12 at 22:52:55 UT (i.e. 11.5 hr after the burst), and lasted for about 1 hour.

From preliminary inspection, we do not detect any possible counterpart consistent with the afterglow (Li et al., GCN 40443; Xin et al., GCN 40444; Busmann et al., GCN 40447) down to the following 3sigma limits:

r > 18.9 (AB; calibrated against the Pan-STARRS catalogue), at a mid-time of 12.0 hr after the trigger;

H > 16.2 (Vega; calibrated against the 2MASS catalogue), at a mid-time of 11.9 hr after the trigger.

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