{
  "bibcode": "2019GCN.23781....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 190123A (D'Ai et al., GCN Circ. 23769) 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 2019-01-24 02:30 to 2019-01-23\n10:56 (from 14.2 to 22.6 hours after the trigger), obtaining a total of\n6.7 hours of exposure in the w filter.\n\nWe do not detect a source at the enhanced XRT position (Beardmore et\nal., GCN Circ. 23771) to a 5-sigma upper limit of w > 22.9.\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\nOur deeper non-detection follows non-detections reported by Lipunov et\nal. (GCN Circ. 23770), Hu et al. (GCN Circ. 23772), Steeghs et al. (GCN\nCirc. 23774), and Shiraishi et al.(GCN Circ. 23778).\n\nWe thank the COATLI technical team and the staff of the Observatorio\nAstron��mico Nacional.",
  "circularId": 23781,
  "createdOn": 1548334270000,
  "email": "alan@astro.unam.mx",
  "subject": "GRB 190123A: COATLI Optical Observations",
  "submitter": "Alan M. Watson at Instituto de Astronomia UNAM  <alan@astro.unam.mx>",
  "eventId": "GRB 190123A"
}