{
  "bibcode": "2014GCN.16076....1B",
  "body": "Nat Butler (ASU), Alan M. Watson (UNAM), Alexander Kutyrev (GSFC), William\nH. Lee (UNAM), Michael G. Richer (UNAM), Chris Klein (UCB), Ori Fox (UCB),\nJ. Xavier Prochaska (UCSC), Josh Bloom (UCB), Antonino Cucchiara\n(ORAU/GSFC), Eleonora Troja (GSFC), Owen Littlejohns (ASU), Enrico\nRamirez-Ruiz (UCSC), Jos� A. de Diego (UNAM), Leonid Georgiev (UNAM), Jes�s\nGonz�lez (UNAM), Carlos Rom�n-Z��iga (UNAM), Neil Gehrels (GSFC), and\nHarvey Moseley (GSFC) report:\n\nWe again observed the field of GRB 140331A (Zhang, et al., GCN 16049) with\nthe Reionization and Transients Infrared Camera (RATIR; www.ratir.org) on\nthe 1.5m Harold Johnson Telescope at the Observatorio Astron�mico Nacional\non Sierra San Pedro M�rtir first from 2014/04 1.13 to 2014/04 1.37 UTC\n(21.27 to 27.13 hours after the BAT trigger), obtaining a total of 3.50\nhours exposure in the r and i bands and 1.46 hours exposure in the Z, Y, J,\nand H bands and then from 2014/04 3.18 to 2014/04 3.36 UTC (70.39 to 74.71\nhours after the BAT trigger), obtaining a total of 2.56 hours exposure in\nthe r and i bands and 1.07 hours exposure in the Z, Y, J, and H bands.\n\nWe do not detect statistically significant flux variation for the source\nreported by Littlejohns et al. (2014, GCN 16050), which was also noted to\nbe coincident with an SDSS galaxy at z~0.7.  We, therefore, conclude that\nthis source is not the GRB afterglow (see, also, Klotz et al. 2014, GCN\n6057).\n\nWe can utilize the observations reported here to estimate the limiting\nmagnitudes for the GRB during our first night of observations (mean time ~1\nhr after the GRB).  For a source within the Swift-XRT error circle\n(Beardmore et al. 2014, GCN 16052) , in comparison with the SDSS DR9 and\n2MASS, we obtain the following (3-sigma) upper limits:\n\n r > 23.5\n i > 23.2\n Z > 21.3\n Y > 21.3\n J > 21.2\n H > 21.0\n\nThese magnitudes are in the AB system and are not corrected for Galactic\nextinction in the direction of the GRB.  The r-band limit implies a very\nfaint or reddened afterglow.  Our r-band limit relative to the X-ray flux\nat the same epoch (e.g., D'Avanzo et al. 2014, GCN 16065) implies a\nbroadband spectral index beta_OX<0.3 (3-sigma), which is significantly\nlower than the standard cuttoff (beta_OX<0.5) defining optically-dark GRBs\n(e.g, Jakobsson et al. 2004).\n\nWe thank the staff of the Observatorio Astron�mico Nacional in San Pedro\nM�rtir.",
  "circularId": 16076,
  "createdOn": 1396548059000,
  "email": "natbutler@asu.edu",
  "subject": "GRB 140331A: Continued RATIR Optical and NIR Observations",
  "submitter": "Nat Butler at Az State U  <natbutler@asu.edu>",
  "eventId": "GRB 140331A"
}