TITLE:   GCN CIRCULAR
NUMBER:  6897
SUBJECT: GRB 071010B: Optical Detection
DATE:    07/10/12 01:52:16 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 GRB071010B (GCN 6871,
  Markwardt et al.) beginning at 11:19:26 UT on Oct 11,
  or 14.3 hrs after the trigger.
   From a stacked image of four, 5 min frames in the R-band,
  we detect the OT (Oksanen GCN 6873, Kann et al. GCN 6884)
  with a high significance (S/N > 15) at the position
  they reported. Compared to the non-detection
  report at 13.6 hrs after the trigger (GCN 6893),
  our detection suggests re-brightening of OT.

   A preliminary photometry of the object using USNO B1.0
  R2 mag of two stars near the OT is given below
  (aperture mag with 6" diameter circle).

  t_start (UT)    Filter    exp (sec)    R-mag   err
-----------------------------------------------------
  11:19:26          R        4x300       19.8    0.08 (uncertain)

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