{
  "submitter": "Margarita Pereyra Talamantes at IA-UNAM Ensenada <mpereyra@astro.unam.mx>",
  "body": "Margarita Pereyra (UNAM), Rosa L. Becerra (U Roma), Stéphane Basa (UAR Pytheas), William H. Lee (UNAM), Jean-Luc Atteia (IRAP),  Dalya Akl (AUS), Camila Angulo (UNAM), Sarah Antier (OCA),  Nathaniel R. Butler (ASU), Jean-Grégoire Ducoin (CPPM), Damien Dornic (CPPM), Francis Fortin (IRAP), Noémie Globus (UNAM), Kin Ocelotl López (UNAM), Diego López-Cámara (UNAM), Francesco Magnani (CPPM), Enrique Moreno Méndez (UNAM), Ny Avo Rakotondrainibe (LAM), Benjamin Schneider (LAM), and Antonio de Ugarte Postigo (LAM) report:\n\nWe imaged the field of the Einstein Probe source EP J120944.2+585060 (Sun et al., GCN Circ. 39834) possibly associated with FRB 250316A (ID=439373176) detected by CHIME/FRB (Mason et al., ATel #[17081](https://www.astronomerstelegram.org/?read=17081) with the DDRAGO wide-field imager on the COLIBRÍ telescope at the Observatorio Astronómico Nacional on the Sierra de San Pedro Mártir in Mexico.\n\nWe observed the field centred in the position of EP J120944.2+585060 from 2025-03-23 08:23:56 to 12:32:11 UTC (6.99 to 7.17 days after the discovery of FRB 250316A) and obtained 2.82 hrs of exposure 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 in the AB system and is not corrected for Galactic extinction.\n\nConsistent with previous reports (Becerra et al. ATel #[17082](https://www.astronomerstelegram.org/?read=17082), Niuno et al. ATel #[17084](https://www.astronomerstelegram.org/?read=17084), Hashimoto et al. ATel #[17095](https://www.astronomerstelegram.org/?read=17095), Aryan et al. Circ. GCN 39839, Yang et al. ATel #[17101](https://www.astronomerstelegram.org/?read=17101), Becerra et al. GCN 39843 and Becerra et al. GCN 39853), we do not detect any uncatalogued source to an estimated 5-sigma upper limit of\n\ni > 23.6 \n\nWe warmly thank the COLIBRÍ and DDRAGO engineering teams and the staff of the Observatorio Astronómico Nacional on the Sierra de San Pedro Mártir.\n",
  "format": "text/markdown",
  "createdOn": 1742793271482,
  "circularId": 39858,
  "submittedHow": "web",
  "bibcode": "2025GCN.39858....1P",
  "subject": "FRB 250316A: COLIBRÍ/DDRAGO Optical follow up of the X ray source EP J120944.2+585060"
}