TITLE: GCN CIRCULAR NUMBER: 39374 SUBJECT: SVOM/sb25021804: COLIBRÍ/DDRAGO Confirmation of Variability DATE: 25/02/19 14:04:46 GMT FROM: Alan Watson at UNAM <alan@astro.unam.mx> Damien Dornic (CPPM), Antonio de Ugarte Postigo (LAM), Alan M. 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), 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 field of SVOM/ECLAIRs trigger sb25021804 (Wang et al., GCN 39363) 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 observed from 2025-02-19 06:23 to 09:00 UTC (23.1 to 25.7 hours after the trigger) and obtained 100 minutes of exposure in the r filter. The data were coadded with custom software and analyzed in 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. For the X-ray bright QSO WISEA J130010.60+280749.7, suggested by Eyles-Ferris et al. (GCN Circ. 39372) as a possible counterpart of the ECLAIRs source, we measure a magnitude of r = 19.95 +/- 0.01 In our observation on the previous night, reported in de Ugarte Postigo et al. (GCN Circ. 39364), we measure i = 19.98 +/- 0.04 Our magnitudes are about 0.3 magnitudes above the mean magnitudes reported in SDSS DR6 and PanSTARRS DR1. This confirms the excess reported by Eyles-Ferris et al. (GCN Circ. 39372) and strengthens their suggestion that this QSO might be related to the SVOM trigger. 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/39374. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0LW...