{
  "body": "Alan M. Watson (UNAM), Owen Littlejohns (ASU), Nat Butler (ASU),\nAlexander Kutyrev (GSFC), William H. Lee (UNAM), Michael G.\nRicher (UNAM), Chris Klein (UCB), Ori Fox (UCB), J. Xavier\nProchaska (UCSC), Josh Bloom (UCB), Antonino Cucchiara (UCSC),\nEleonora Troja (GSFC), Enrico Ramirez-Ruiz (UCSC), José A. de\nDiego (UNAM), Leonid Georgiev (UNAM), Jesús González (UNAM),\nCarlos Román-Zúñiga (UNAM), Neil Gehrels (GSFC), and Harvey\nMoseley (GSFC) report:\n\nWe again observed the field of GRB 130831A (Hagen, et al., GCN 15139) with\nthe Reionization and Transients Infrared Camera (RATIR; www.ratir.org) on\nthe 1.5m Harold Johnson Telescope at the Observatorio Astronómico Nacional\non Sierra San Pedro Mártir from 2013/09 4.32 to 2013/09 4.34 UTC (90.60\nto 91.04 hours after the BAT trigger), obtaining a total of 0.36 hours\nexposure in the r' and i' bands and 0.15 hours exposure in the Z,\nY, J, and H bands.\n\nFor a source within the Swift-XRT error circle (Evans et al., GCN 15147),\nin comparison with SDSS DR9 and 2MASS, we obtain the following upper limits\n(3-sigma):\n\n  r'    > 22.84\n  i'    > 22.94\n  Z     > 20.76\n  Y     > 20.23\n  J     > 20.09\n  H     > 19.49\n\nIn comparison with earlier RATIR observations (Butler et al., GCN 15165)\nthe source has faded by 2.2 magnitudes in the r' band and 2.6 magnitudes\nin the i' band. This implies a power-law decay steeper than t^-1.7. The\nupper limits obtained in the Z, Y, J, and H bands are also consistent with\nsuch a steep decay index. These magnitudes are in the AB system and not\ncorrected for Galactic extinction in the direction of the GRB.\n\nWe thank the staff of the Observatorio Astronómico Nacional in San Pedro\nMártir.",
  "email": "olittlej@asu.edu",
  "editedOn": 1731009255954,
  "editedBy": "Vidushi Sharma at NASA GSFC/UMBC <vidushi.sharma@nasa.gov> on behalf of Leo P. Singer at NASA/GSFC <leo.p.singer@nasa.gov>",
  "version": 2,
  "circularId": 15179,
  "createdOn": 1378320234000,
  "format": "text/plain",
  "bibcode": "2013GCN.15179....1W",
  "subject": "GRB 130831A: RATIR Optical and NIR Upper Limits",
  "submitter": "Owen Littlejohns at Az State U  <olittlej@asu.edu>",
  "eventId": "GRB 130831A"
}