TITLE: GCN CIRCULAR NUMBER: 40382 SUBJECT: GRB 250506A: SVOM/COLIBRÍ (FM-GFT) optical upper limit DATE: 25/05/07 14:39:13 GMT FROM: J.-G. Ducoin at CPPM <ducoin@cppm.in2p3.fr> Jean-Grégoire Ducoin (CPPM), Alan M. Watson (UNAM), Fredd Alvarez (UNAM), Stéphane Basa (UAR Pytheas), William H. Lee (UNAM), Jean-Luc Atteia (IRAP), Camila Angulo (UNAM), Dalya Akl (AUS), Sarah Antier (OCA), Rosa L. Becerra (U Roma), Nathaniel R. Butler (ASU) , Damien Dornic (CPPM), Francis Fortin (IRAP), Noémie Globus (UNAM), Kin Ocelotl López (UNAM), Diego López-Cámara (UNAM), Francesco Magnani (CPPM), Enrique Moreno Méndez (UNAM), Margarita Pereyra (UNAM), Ny Avo Rakotondrainibe (LAM), Benjamin Schneider (LAM), Antonio de Ugarte Postigo (LAM), Chenwei WANG (IHEP) and Lin LAN (NAOC): We imaged the field of the SVOM GRB 250506A (Wang et al., GCN Circ. 40358) using the DDRAGO wide-field imager on the SVOM/COLIBRÍ (FM-GFT) telescope. We observed from 2025-05-07T03:44:16 to 05:14:17 UTC (from 1.12 to 1.22 days after the trigger) and obtained 64 minutes of exposure in the i filter. The data were reduced and coadded with the COLIBRÍ pipeline and analyzed with STDWeb/STDPipe (Karpov 2025). The photometry was calibrated using nearby stars from the PanSTARRS DR1 catalog and is not corrected for Galactic extinction. In the stacked image, we do not detect any new source at the improved MXT position (Maggi et al., GCN Circ. 40364) and at the XRT position (Burrows et al., GCN Circ. 40378) down to the following 5-sigma limit (AB): i > 22.4 This upper limit is consistent with the one reported by Xin et al. (GCN Circ. 40366), Ferro et al. (GCN Circ. 40363), Liu et al. (GCN Circ. 40360), Postigo et al. (GCN Circ. 40359), and Liu et al. (GCN Circ. 40373). We thank the staff of the Observatorio Astronómico Nacional on the Sierra de San Pedro Mártir and the COLIBRÍ and DDRAGO engineering teams. COLIBRÍ is an astronomical observatory developed and operated jointly by France (AMU, CNES and CNRS) and Mexico (UNAM and SECIHTI). It is located at the Observatorio Astronómico Nacional on the Sierra de San Pedro Mártir, Baja California, Mexico. View this GCN Circular online at https://gcn.nasa.gov/circulars/40382. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0LW...