TITLE:   GCN CIRCULAR
NUMBER:  6920
SUBJECT: GRB 071010B: Photometry after 1.6 days
DATE:    07/10/16 01:37:25 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 continued our observation of GRB071010B (GCN 6871,
  Markwardt et al.), beginning at 11:37:19 UT on Oct 12,
  or 1.62 days after the trigger.
   From a stacked image of nine, 5 min frames in the R-band,
  we detect the OT again (Oksanen GCN 6873, Kann et al. GCN 6884).

   A preliminary photometry of the object using the standard
  star data taken during the same day is given below
  (aperture mag with 6" diameter circle). Also given is a
  slightly revised R-band magnitude we reported earlier
  (Im et al., GCN 6897).


  t_start (UT)    Filter    exp (sec)    R-mag   err
-----------------------------------------------------
  Oct. 11,
  11:19:47          R        4x300       19.81    0.08

  Oct. 12,
  11:37:19          R        9x300       20.54    0.10

   Our result is consistent with the recent report that
  the GRB is fading rather slowly (GCN 6918, Kann et al.;
  GCN 6919 Kocevski et al.).  However, compared with
  the magnitudes at Oct. 14 reported by Kann et al. (6918),
  our photometry suggests a very marginal decrease in
  the brightness between Oct. 12 - Oct. 14.

   We will report later, the BVRI photometry data
  taken during the same period.

   This message may be cited.