{
  "submittedHow": "email",
  "body": "Alan M. Watson (UNAM), Camila Angulo (UNAM), D. Akl (AUS), S. Antier\n(OCA), Benjamin Schneider (LAM), Stéphane Basa (UAR Pytheas), William\nH. Lee (UNAM), Jean-Luc Atteia (IRAP), Rosa Becerra (Università degli\nStudi di Roma Tor Vergata), Nathaniel R. Butler (ASU), Damien Dornic\n(CPPM), Francis Fortin (IRAP), J.-G. Ducoin (CPPM), Francesco Magnani\n(CPPM) and Margarita Pereyra (UNAM) report:\n\nWe imaged the field of the Swift GRB 250129A (Beardmore et al., GCN\nCirc. 39066) during the commissioning of the COLIBRÍ (SVOM/F-GFT)\ntelescope at the Observatorio Astronómico Nacional on the Sierra de\nSan Pedro Mártir in Mexico.\n\nWe observed with the OGSE engineering test camera in a red filter that\napproximates SDSS r from 2025-01-30 07:01 to 12:54 UTC. In the subset\nof our data from 2025-01-30 12:01 to 12:54, from 31.27 to 32.15 hours\nafter the event, with a total exposure of 2220 seconds, we clearly\ndetect the afterglow with\n\nr = 19.38 +/- 0.04\n\nThis magnitude is not corrected for Galactic extinction. The data were\nreduced using custom software and then analysed and calibrated against\nthe PS1 catalog using the STDWeb service.\n\nFurther observations are planned.\n\nWe warmly thank the COLIBRÍ engineering team and the staff of the\nObservatorio Astronómico Nacional on the Sierra de San Pedro Mártir.\nWe warmly thank the GRANDMA IJCLAB team and S. Karpov for the access\nof the STDWeb service for STDPipe.\n",
  "createdOn": 1738307612107,
  "submitter": "Alan Watson at UNAM <alan@astro.unam.mx>",
  "eventId": "GRB 250129A",
  "subject": "GRB 250129A: COLIBRÍ Optical Observations",
  "bibcode": "2025GCN.39104....1W",
  "circularId": 39104
}