{
  "bibcode": "2021GCN.30672....1B",
  "body": "Nat Butler (ASU), Alan M. Watson (UNAM), Alexander Kutyrev (GSFC), William\nH.\nLee (UNAM), Eleonora Troja (GSFC), Michael G. Richer (UNAM), Ori Fox\n(STScI),\nJ. Xavier Prochaska (UCSC), Josh Bloom (UCB), Enrico Ramirez-Ruiz (UCSC),\nJes��s Gonz��lez (UNAM), Carlos Rom��n-Z����iga (UNAM), Harvey Moseley (GSFC),\nRosa\nL. Becerra (UNAM), Simone Dichiara (UMD), and Oc��lotl L��pez (UNAM) report:\n\nWe observed the field of GRB 210820A (Beardmore, et al., GCN 30664) with\nthe\nReionization and Transients Infrared Camera (RATIR) on the 1.5m Harold\nJohnson Telescope at the Observatorio Astron��mico Nacional on Sierra San\nPedro M��rtir from 2021/08 21.27 to 2021/08 21.50 UTC (12.47 to 17.96\nhours after the BAT trigger), obtaining a total of 3.70 hours exposure\nin the r and i bands.\n\nWe detect one source within the Swift-XRT error circle (Beardmore, et al.,\nGCN 30667).  In comparison with the SDSS DR9 and 2MASS catalogs, we obtain:\n\n  r = 22.84 +/- 0.22\n  i = 22.66 +/- 0.18\n\nThese magnitudes are in the AB system and are not corrected for Galactic\nextinction in the direction of the GRB.\n\nThe source is located at RA, Dec = 1:22:33.47, +4:36:28.1 (J2000, +/-0.5\").\nThis is 0.2 arcsec away from the UVOT OT (GCN 30664).\n\nWe thank the staff of the Observatorio Astron��mico Nacional in San Pedro\nM��rtir.",
  "circularId": 30672,
  "createdOn": 1629561148000,
  "email": "natbutler@asu.edu",
  "subject": "GRB 210820A: RATIR Optical Detections",
  "submitter": "Nat Butler at Az State U  <natbutler@asu.edu>",
  "eventId": "GRB 210820A"
}