{
  "bibcode": "2019GCN.23864....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 190203A (Lien et al., GCN Circ. 23845) 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 02:39 to 2019-02-04\n09:19 (from 10.9 to 17.6 hours after the trigger), obtaining a total of\n3.2 hours of exposure in the w filter.\n\nAt the position of the UVOT afterglow candidate (Lien et al., GCN Circ.\n23852), we do not detect anything to a 5-sigma limit of w = 22.4.\n\nOur non-detection is consistent with the rapid fading seen by Lien et\nal. (GCN Circ. 23845), Novichonok et al. (GCN Circ. 23846), Moskvitin et\nal. (GCN Circ. 23847), and Lipunov (GCN Circ. 23850).\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": 23864,
  "createdOn": 1549290061000,
  "email": "alan@astro.unam.mx",
  "subject": "GRB 190203A: COATLI Optical Observations",
  "submitter": "Alan M. Watson at Instituto de Astronomia UNAM  <alan@astro.unam.mx>",
  "eventId": "GRB 190203A"
}