TITLE: GCN CIRCULAR NUMBER: 39371 SUBJECT: GRB 250217C: COLIBRÍ/DDRAGO Upper Limits on the Optical Counterpart DATE: 25/02/19 07:20:09 GMT FROM: Alan Watson at UNAM <alan@astro.unam.mx> Alan M. Watson (UNAM), Antonio de Ugarte Postigo (LAM), Eleonora Troja (U Roma), Rosa L. Becerra (U Roma), Simone Dichiara (PSU), Stéphane Basa (UAR Pytheas), William H. Lee (UNAM), Dalya Akl (AUS), Camila Angulo (UNAM), Sarah Antier (OCA), Jean-Luc Atteia (IRAP), Nathaniel R. Butler (ASU), Damien Dornic (CPPM), Jean-Grégoire Ducoin (CPPM), Francis Fortin (IRAP), Noémie Globus (UNAM), Kin Ocelotl López (UNAM), Francesco Magnani (CPPM), Margarita Pereyra (UNAM), Ny Avo Rakotondrainibe (LAM), and Benjamin Schneider (LAM) report: We imaged the IPN 3-sigma error box of GRB 250217C (Fermi GBM Team, GCN Circ. 39357, Tembhurnikar et al., GCN Circ. 39359, Kozyrev et al., GCN Circ. 39365) with the DDRAGO wide-field imager on the COLIBRÍ telescope at the Observatorio Astronómico Nacional on the Sierra de San Pedro Mártir in Mexico. We used three pointings that, combined with the 26 arcmin field of COLIBRÍ/DDRAGO, cover more than 95% of the IPN error box. We observed from 2025-02-19 02:51 to 04:18 UTC (27.0 to 28.4 hours after the trigger) and obtained 20 minutes of exposure at each pointing in the i filter. The data were coadded with custom software and analyzed in STDWeb/STDPipe (Karpov 2021), with photometric calibration against Pan-STARRS DR1 and image subtraction against Pan-STARRS DR2. Our photometry is not corrected for Galactic extinction. We do not detect any likely optical counterpart to a 5-sigma limit of i > 22.7 Our non-detections are consistent with the shallower limits reported by Becerra et al. (GCN Circ. 39370) and with the lack of a bright X-ray candidate counterpart in the tiled Swift/XRT ToO observations reported by Evans et al. (GCN Circ. 39368). We warmly thank the COLIBRÍ and DDRAGO engineering teams and the staff of the Observatorio Astronómico Nacional on the Sierra de San Pedro Mártir. View this GCN Circular online at https://gcn.nasa.gov/circulars/39371. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0LW...