{
  "subject": "GRB 250205A: COLIBRÍ/DDRAGO Optical Afterglow Detection",
  "submittedHow": "email",
  "createdOn": 1738818418776,
  "circularId": 39162,
  "body": "Alan M. Watson (UNAM), Stéphane Basa (UAR Pytheas), William H. Lee\n(UNAM), Dalya Akl (AUS), Camila Angulo (UNAM), Sarah Antier (OCA),\nJean-Luc Atteia (IRAP), Rosa L. Becerra (Università degli Studi di\nRoma Tor Vergata), Nathaniel R. Butler (ASU), Damien Dornic (CPPM),\nFrancis Fortin (IRAP), Jean-Grégoire Ducoin (CPPM), Francesco Magnani\n(CPPM), Margarita Pereyra (UNAM), and Benjamin Schneider (LAM) report:\n\nWe imaged the field of the SVOM/ECLAIRs GRB 250205A (Saccardi et al.,\nGCN Circ. 39154) with the DDRAGO wide-field camera on the COLIBRÍ\n(SVOM/F-GFT) telescope at the Observatorio Astronómico Nacional on the\nSierra de San Pedro Mártir in Mexico.\n\nWe observed from 2025-02-06 03:01 to 04:48 UTC, with a midpoint of\n6.34 hours after the event, and obtained 3840 seconds of exposure in\nthe r filter in good weather conditions. The data were reduced and\nstacked using custom software and then calibrated against the PS1\ncatalog and analysed using STDPipe (Karpov 2021).\n\nWe detect the afterglow (Gompertz et al., GCN Circ. 39156, and\nSchneider & Adami, GCN Circ. 39157) with\n\nr = 22.89 +/- 0.11\n\nThis magnitude is not corrected for Galactic extinction.\n\nOur measurement is significantly fainter than the earlier r magnitudes\nreported by Gompertz et al. (GCN Circ. 39156), Schneider & Adami (GCN\nCirc. 39157), Palmerio et al. (GCN Circ. 39159), and de Ugarte Postigo\net al. (GCN Circ. 39160), confirming that this is the afterglow.\nCompared to the magnitude reported by de Ugarte Postigo et al., our\nmeasurement implies a temporal index of -0.80 +/- 0.08 between 1.76\nand 6.34 hours.\n\nFurther observations are planned.\n\nWe warmly thank the COLIBRÍ and DDRAGO engineering teams and the staff\nof the Observatorio Astronómico Nacional on the Sierra de San Pedro\nMártir.\n",
  "submitter": "Alan Watson at UNAM <alan@astro.unam.mx>",
  "eventId": "GRB 250205A",
  "bibcode": "2025GCN.39162....1W"
}