{
  "bibcode": "2018GCN.22859....1W",
  "body": "Alan M. Watson (UNAM), Nat Butler (ASU), Rosa L. Becerra (UNAM), William\nH. Lee (UNAM), Carlos Rom��n-Z����iga (UNAM), Alexander Kutyrev (GSFC), and\nEleonora Troja (GSFC) report:\n\nWe observed the field of GRB 180626A (Evans et al., GCN 22850) with the\nCOATLI 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 2018-06-20 08:21:50.6 to\n11:18:41.7 UTC (from 33.7 seconds after the trigger or 17.9 seconds\nafter the alert to 2.95 hours after the trigger), obtaining a total of\n7020 seconds of exposure in the w filter.\n\nWithin the enhanced XRT error region (Osborne et al., GCN Circ. 22852),\nwe detect the afterglow previously reported by Evans et al. (GCN Circ.\n22850), Martone et al. (GCN Circ. 22854), and Breeveld et al. (GCN Circ.\n22857) with\n\n  w = 21.4 +/- 0.9\n\nIn our first set of 30 images each of 5 seconds of exposure, from\n08:21:50.6 to 08:27:10.1 UTC, we do not detect the afterglow with a\n10-sigma limiting magnitude of\n\n  w > 19.2\n\nThese magnitudes are calibrated against the Pan-STARRS1 catalog and the\nUSNO-B1 catalog (adjusted to an approximate AB system) and are not\ncorrected for Galactic extinction in the direction of the GRB.\n\nWe thank the COATLI technical team (Fernando ��ngeles, Oscar Chapa,\nSalvador Cuevas, Alejandro Farah, Jorge Fuentes, Rosal��a Langarica,\nFernando Quir��s, and Carlos Tejada) and the staff of the Observatorio\nAstron��mico Nacional.",
  "circularId": 22859,
  "createdOn": 1530033010000,
  "email": "alan@astro.unam.mx",
  "subject": "GRB 180626A: COATLI Optical Detection",
  "submitter": "Alan M. Watson at Instituto de Astronomia UNAM  <alan@astro.unam.mx>",
  "eventId": "GRB 180626A"
}