{
  "bibcode": "2017GCN.22042....1B",
  "body": "Nat Butler (ASU), Alan M. Watson (UNAM), Alexander Kutyrev (GSFC), William\nH. Lee (UNAM), Michael G. Richer (UNAM), Ori Fox (STScI), J. Xavier\nProchaska (UCSC), Josh Bloom (UCB), Antonino Cucchiara (UVI), Eleonora\nTroja (GSFC), Owen Littlejohns (ASU), Enrico Ramirez-Ruiz (UCSC), Jes��s\nGonz��lez (UNAM), Carlos Rom��n-Z����iga (UNAM), Harvey Moseley (GSFC), John\nCapone (UMD), V. Zach Golkhou (U. Wash.), and Vicki Toy (UMD) report:\n\nWe observed the field of GRB 171020A (Page, et al., GCN 22028) with the\nReionization and Transients Infrared Camera (RATIR; www.ratir.org) on the\n1.5m Harold Johnson Telescope at the Observatorio Astron��mico Nacional on\nSierra San Pedro M��rtir from 2017/10 22.13 to 2017/10 22.47 UTC (27.94 to\n36.23 hours after the BAT trigger), obtaining a total of 5.27 hours\nexposure in the r and i bands and 2.21 hours exposure in the Z and Y bands.\n\nWe contine to detect the optical transient (Malesani, et al., GCN 22029;\nalso, Moskvitin, et al., GCN 22031; Butler, et al., GCN 22037).  In\ncomparison with the USNO-B1 and 2MASS catalogs, we obtain the following\ndetections and upper limits (3-sigma):\n\n r = 23.25 +/- 0.14\n i = 23.01 +/- 0.11\n Z > 21.75\n Y > 22.05\n\nThese magnitudes are in the AB system and are not corrected for Galactic\nextinction in the direction of the GRB.  Compared to our observations last\nnight, these data suggest either a slow afterglow fade (~t^-0.2) or that\nour measured flux contains flux from the GRB host galaxy.\n\nWe thank the staff of the Observatorio Astron��mico Nacional in San Pedro\nM��rtir.",
  "circularId": 22042,
  "createdOn": 1508707140000,
  "email": "natbutler@asu.edu",
  "subject": "GRB 171020A: Continued RATIR Optical and NIR Observation",
  "submitter": "Nat Butler at Az State U  <natbutler@asu.edu>",
  "eventId": "GRB 171020A"
}