TITLE: GCN CIRCULAR NUMBER: 40169 SUBJECT: GRB 250419A: SVOM/COLIBRÍ (FM-GFT) Detection of the Optical Counterpart DATE: 25/04/19 04:51:59 GMT FROM: Alan Watson at UNAM alan@astro.unam.mx
Kin Ocelotl López (UNAM), Alan Watson (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), Jean-Grégoire Ducoin (CPPM), Francis Fortin (IRAP), Noémie Globus (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), and B.-T. Wang (YNAO, CAS) report:
We imaged the field of the SVOM GRB 250419A (Wang et al., GCN Circ. 40168) with the DDRAGO wide-field imager on the SVOM/COLIBRÍ (FM-GFT) telescope at the Observatorio Astronómico Nacional on the Sierra de San Pedro Mártir in Mexico on the night of 2025-04-19 UTC.
We observed from 2025-04-19 03:04 to 03:07 (35 to 38 minutes after the trigger) and obtained 3 minutes of exposure in the i filter. The data were coadded with the COLIBRÍ pipeline and analysed in STDWeb/STDPipe (Karpov 2025), with photometric calibration against Pan-STARRS DR1. Our photometry is in the AB system and is not corrected for Galactic extinction.
We detect an uncataloged source at RA, Dec = 202.40535, 7.04108 degrees (J2000) with a magnitude of
i = 17.87 +/- 0.01
We suggest this is the optical counterpart of the GRB.
Further observations and analysis are ongoing.
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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