TITLE:   GCN CIRCULAR
NUMBER:  7018
SUBJECT: GRB071025: Optical+NIR observations
DATE:    07/10/29 23:02:05 GMT
FROM:    Paul Price at IfA,UH  <price@ifa.hawaii.edu>

T. Minezaki (IoA, Tokyo), P.A. Price (IfA, Hawaii), Y. Yoshii (IoA,
Tokyo), L. Cowie (IfA, Hawaii) and Y. Kakazu (IfA, Hawaii) report:

We observed the optical afterglow of GRB071025 with the robotic MAGNUM
telescope + MIPS dual-beam imager.  We find a fading source in each of
the RIYJHK bands at the position reported by Bloom et al. (GCN 6989):

 Filter  midtime(UTC)       Exp. time    magnitude/upper limits
   J     2007-10-25 06:59   10           17.73 +- 0.06
   R     2007-10-25 07:01   10           21.5  +- 0.4
   Y     2007-10-25 07:21    9           detected
   I     2007-10-25 07:21   10           19.97 +- 0.13
   K     2007-10-25 07:43    8           16.67 +- 0.07
   R     2007-10-25 07:43   10           > 20.9
   H     2007-10-25 08:04    9           17.59 +- 0.08
   I     2007-10-25 08:04   10           20.3 +- 0.2
   J     2007-10-25 08:25    9           18.29 +- 0.10
   R     2007-10-25 08:25   10           > 21.0
   Y     2007-10-25 08:44    9           marginally detected
   I     2007-10-25 08:44   10           20.5 +- 0.3


The magnitude and the 3-sigma upper limits were derived using the
USNO-B1.0 and 2MASS catalogues. The magnitude error does not include the
error of the calibration source. The Y-band observations have not been
calibrated.

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