{
  "bibcode": "2018GCN.22528....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 180324A (Sonbas, et al., GCN 22524) 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 2018/03 24.19 to 2018/03 24.23 UTC (2.4\nminutes to 0.92 hours after the BAT trigger), obtaining a total of 0.66\nhours exposure in the r and i bands.\n\nWe detect a weak source within the Swift-XRT error circle (Evans, et al.,\nGCN 22525) in our first 80 s exposure, i-band image only.  In comparison\nwith the USNO-B1 catalog, we find i=20.15+/-0.37.\n\nThe source is not on the frame in the subsequent image and is not detected\nin the next possible frame 3.5 minutes later.  In our full 0.66 hour\nexposure time, the source is not detected with the following upper limits\n(3-sigma):\n\n  r > 22.08\n  i > 22.04\n\nThese magnitudes are in the AB system and are not corrected for Galactic\nextinction in the direction of the GRB.  If the detection in the first\nframe is due to the afterglow, then the afterglow faded rapidly.\n\nWe thank the staff of the Observatorio Astron��mico Nacional in San Pedro\nM��rtir.",
  "circularId": 22528,
  "createdOn": 1521875796000,
  "email": "natbutler@asu.edu",
  "subject": "GRB 180324A: RATIR Optical Observations and Possible Afterglow Detection",
  "submitter": "Nat Butler at Az State U  <natbutler@asu.edu>",
  "eventId": "GRB 180324A"
}