TITLE: GCN CIRCULAR NUMBER: 40938 SUBJECT: GRB 250407A: REM detection of the optical afterglow DATE: 25/07/04 07:59:57 GMT FROM: Riccardo Brivio at INAF-OAB <riccardo.brivio@inaf.it> R. Brivio, M. Ferro (INAF-OAB), S. D. Vergani (LUX-Paris Obs.), A. Melandri (INAF-OAR), P. D'Avanzo, S. Covino, D. Fugazza (INAF-OAB) report on behalf of the REM team: We observed the field of GRB 250704A detected by SVOM (Cao et al., GCN 40934) 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 July 04 at 05:19:02 UT (i.e. 1.6 hr after the burst), and lasted for about 2 hours. From preliminary inspection, we detect the optical afterglow within the SVOM/MXT error region at the coordinates (J2000): RA = 01:08:46.5 Dec = -17:19:28.0 and with the following magnitude: r = 17.6 +/- 0.2 (AB; calibrated against the Pan-STARRS catalogue), at a mid-time of 1.7 hr after the trigger. No NIR counterpart is detected down to the following 3sigma upper limit: H > 15.6 (Vega; calibrated against the 2MASS catalogue), at a mid-time of 1.8 hr after the trigger. View this GCN Circular online at https://gcn.nasa.gov/circulars/40938. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0LW...