{
  "bibcode": "2009GCN..9008....1C",
  "body": "B. E. Cobb (UC Berkeley) reports:\n\nUsing the ANDICAM instrument on the 1.3m telescope at CTIO, we obtained\noptical/IR imaging of the error region of GRB 090313 (GCN 8980, Mao\net al.) over four epochs (with UT mid-exposure times of: 2009-03-14 04:27,\n2009-03-14 06:55, 2009-03-15 06:30 & 2009-03-17 05:07). Total\nsummed exposure times for each observation amounted to\n36 minutes in R and 30 minutes in J.\n\nThe GRB afterglow (e.g. GCN 8979, Chornock et al., GCN 8983, Updike et\nal. and GCN 8985, Perley et al.) appears in our imaging to be fading \nrapidly after ~19 hours post-burst:\n\nmid-exposure time\n(hours post-burst)   R mag           J mag\n19.33                19.70+/-0.04    17.38+/-0.15\n21.81                19.90+/-0.04    17.62+/-0.15\n45.38                21.57+/-0.12    18.91+/-0.16\n92.01                > 22.5          > 19.8\n\nThese preliminary magnitudes are calibrated using Landolt standard\nstars in the optical and a 2MASS star in the IR.\n\nThis rapid fading follows the initial plateau phase that was reported by \nPerley et al. (GCN 8985) and de Ugarte Postigo et al. (GCN 8992).  This \nfading is consistent with the light curve break noted by de Ugarte \nPostigo et al. (GCN 8999), though the break appears to occur in this \nimaging somewhat earlier than suggested by Yoshida et al. (GCN 9002).",
  "circularId": 9008,
  "createdOn": 1237338389000,
  "email": "bcobb@astro.berkeley.edu",
  "subject": "GRB 090313, SMARTS optical/IR observations",
  "submitter": "Bethany Cobb at UC Berkeley  <bcobb@astro.berkeley.edu>",
  "eventId": "GRB 090313"
}