{
  "bibcode": "2016GCN.18956....1W",
  "body": "Alan M. Watson (UNAM), Nat Butler (ASU), Alexander Kutyrev (GSFC),\nWilliam H. Lee (UNAM), Michael G. Richer (UNAM), Ori Fox (STScI), J.\nXavier Prochaska (UCSC), Josh Bloom (UCB), Antonino Cucchiara\n(GSFC/STScI), Eleonora Troja (GSFC), Owen Littlejohns (ASU), Enrico\nRamirez-Ruiz (UCSC), Jos�� A. de Diego (UNAM), Leonid Georgiev (UNAM),\nJes��s Gonz��lez (UNAM), Carlos Rom��n-Z����iga (UNAM), Neil Gehrels (GSFC),\nHarvey Moseley (GSFC), John Capone (UMD), V. Zach Golkhou (ASU), and\nVicki Toy (UMD) report:\n\nWe observed the field of GRB 160131A (Page et al., GCN Circular 18951)\nwith the Reionization and Transients Infrared Camera (RATIR;\nwww.ratir.org) on the 1.5m Harold Johnson Telescope at the Observatorio\nAstron��mico Nacional on Sierra San Pedro M��rtir from 2016/01 31.35 to\n2016/01 31.37 UTC (0.07 to 0.50 hours after the BAT trigger), obtaining\na total of 0.18 hours exposure in the r, i, and z bands.\n\nWe detect a bright uncatalogued source at 05:12:40.33 -07:03:00 (J2000,\n��0.5 arcsec). In comparison with the USNO-B1 catalog, we obtain the\nfollowing mean magnitudes:\n\n r\t= 13.35 �� 0.04\n i\t= 13.01 �� 0.02\n z\t= 12.67 �� 0.04\n\nThese magnitudes are in the AB system and are not corrected for Galactic\nextinction in the direction of the GRB.\n\nThe source fades roughly as t^-0.87 during our observations. This source\nis presumably the optical counterpart reported by Page et al. (GCN\nCircular 18951), Yurkov et al. (GCN Circular 18952), Guidorzi et al.\n(GCN Circular 18953), and Xin et al. (GCN Circular 18954).\n\nWe thank the staff of the Observatorio Astron��mico Nacional in San Pedro\nM��rtir.",
  "circularId": 18956,
  "createdOn": 1454247418000,
  "email": "alan@astro.unam.mx",
  "subject": "GRB 160131A: RATIR Optical Observations",
  "submitter": "Alan M. Watson at Instituto de Astronomia UNAM  <alan@astro.unam.mx>",
  "eventId": "GRB 160131A"
}