{
  "bibcode": "2018GCN.22934....1B",
  "body": "Nat Butler (ASU), Alan M. Watson (UNAM), aRosa 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 180709A (Marshall et al., GCN Circ 22930) with\nthe COATLI 50-cm telescope and interim imager at the Observatorio\nAstron��mico Nacional on the Sierra de San Pedro M��rtir (\nhttp://coatli.astroscu.unam.mx) from 2018-07-09 10:53:05.6 to 11:26:07.1\nUTC (from 65.4 seconds after the trigger or 14.5 seconds after the alert to\n0.55 hours after the trigger), obtaining a total of 695 seconds of exposure\nin the w filter.\n\nFor a source within the XRT error region (Marshall et al., GCN Circ.\n22930), we determine a 3-sigma upper limit of\n\n w > 21.3\n\nThis magnitude is calibrated against the USNO-B1 catalog (adjusted to an\napproximate AB system) and is not corrected for Galactic extinction in the\ndirection of the GRB.\n\nWe thank the COATLI technical team (Fernando ��ngeles, Oscar Chapa, Salvador\nCuevas, Alejandro Farah, Jorge Fuentes, Rosal��a Langarica, Fernando Quir��s,\nand Carlos Tejada) and the staff of the Observatorio Astron��mico Nacional.",
  "circularId": 22934,
  "createdOn": 1531150062000,
  "email": "natbutler@asu.edu",
  "subject": "GRB 180709A: COATLI Optical Observations",
  "submitter": "Nat Butler at Az State U  <natbutler@asu.edu>",
  "eventId": "GRB 180709A"
}