TITLE: GCN CIRCULAR NUMBER: 39840 SUBJECT: GRB 250321B: SVOM/COLIBRÍ (F-GFT) follow-up observations DATE: 25/03/22 19:49:21 GMT FROM: Ny Avo Rakotondrainibe at LAM nyavo.rakotobe@gmail.com
Jean-Grégoire Ducoin (CPPM), Ny Avo Rakotondrainibe (LAM), Ramandeep Gill (UNAM), Stéphane Basa (UAR Pytheas), William H. Lee (UNAM), Dalya Akl (AUS), Camila Angulo (UNAM), Sarah Antier (OCA), Jean-Luc Atteia (IRAP), 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), Benjamin Schneider (LAM), Antonio de Ugarte Postigo (LAM), Alan M. Watson (UNAM), and Stéphane Schanne (CEA) report:
We imaged the field of the SVOM/ECLAIRs GRB 250321B (Schanne et al., GCN Circ. 39818) with the DDRAGO imager on the SVOM/COLIBRÍ (formerly SVOM/F-GFT) telescope at the Observatorio Astronómico Nacional on the Sierra de San Pedro Mártir in Mexico.
We observed from 2025-03-22 08:07 to 10:20 UTC (28.52 to 30.74 hours after the trigger) and obtained 100 minutes of exposure in the i band. The data were coadded with the COLIBRÍ pipeline and analysed with STDWeb/STDPipe (Karpov 2021), with photometric calibration against Pan-STARRS DR1. Our photometry is in the AB system and is not corrected for Galactic extinction.
Within the ECLAIRs localization of the source (Schanne et al., GCN Circ. 39818) we do not detect any uncatalogued sources to a 10-sigma limiting magnitude of :
i > 22.68
We warmly thank the COLIBRÍ and DDRAGO engineering teams and the staff of the Observatorio Astronómico Nacional on the Sierra de San Pedro Mártir.
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