TITLE:   GCN CIRCULAR
NUMBER:  6905
SUBJECT: GRB 071011: Optical Limit after 13.95hrs
DATE:    07/10/13 01:54:53 GMT
FROM:    Myungshin Im at Seoul Nat U  <mim@astro.snu.ac.kr>

  M. Im, I. Lee (Seoul National University), and Y. Urata
  (Saitama University) on behalf of the EAFON team:

   Using the Mt. Lemmon (Arizona, US) 1.0m telescope
  operated by the Korea Astronomy Space Science Institute,
  we observed the field of GRB071011 (GCN 6882,
  Barthelmy et al.) beginning at 02:37:30 UT on Oct 12,
  or 13.95 hrs after the trigger.
   A stacked image of 11, 5 min frames in the R-band
  does not show the OT reported by Cenko et al. (6895),
  Perley et al. (6898), Pandey et al. (6899), Iizuka
  et al. (6900), and Xin et al. (6904).
   Using USNO B1.0 R2mag of stars for photometric calibration,
   we place the upper limit of the OT as R > 21.9 mag
  (3-sigma, 6" aperture mag) 13.95 hrs after the trigger.
   It appears that the OT faded beyond the R limit.

  t_start (UT)    Filter    exp (sec)    R-mag 
-----------------------------------------------------
  02:37:30          R       11x300       > 21.9mag (3-sigma)

  We will report later, a more careful analysis of the BVRI
  images taken during the same period.