{
  "bibcode": "2019GCN.23861....1W",
  "body": "Alan M. Watson (UNAM), Nat Butler (ASU), Rosa L. Becerra (UNAM), Diego\nGonz��lez (UNAM), William H. Lee (UNAM), Margarita Pereyra (UNAM), Carlos\nRom��n-Z����iga (UNAM), Alexander Kutyrev (GSFC), and Eleonora Troja (GSFC)\nreport:\n\nWe observed the field of GRB 190204A (Lien et al., GCN Circ. 23852) with\nthe COATLI 50-cm telescope and interim imager at the Observatorio\nAstron��mico Nacional on the Sierra de San Pedro M��rtir\n(http://coatli.astroscu.unam.mx) from 2019-02-04 05:46:35 to 2019-02-04\n05:57:30 (from 34 to 689 seconds after the trigger), obtaining a total\nof 345 seconds of exposure in the w filter.\n\nAt the position of the UVOT afterglow candidate (Lien et al., GCN Circ.\n23852), we detect a source that fades from w = 13.5 to w = 17.5 over the\ncourse of our observations. A power-law fit suggest a temporal index of\n-1.44 +/- 0.03.\n\nOur w magnitudes are calibrated against the USNO-B1 catalog (adjusted to\nan approximate AB system) and are not corrected for Galactic extinction\nin the direction of the GRB.\n\nWe thank the COATLI technical team and the staff of the Observatorio\nAstron��mico Nacional.",
  "circularId": 23861,
  "createdOn": 1549284875000,
  "email": "alan@astro.unam.mx",
  "subject": "GRB 190204A: COATLI Optical Detection of the Fading Afterglow",
  "submitter": "Alan M. Watson at Instituto de Astronomia UNAM  <alan@astro.unam.mx>",
  "eventId": "GRB 190204A"
}