TITLE:   GCN CIRCULAR
NUMBER:  9769
SUBJECT: GRB 090812: P60 Confirmation of Optical Afterglow
DATE:    09/08/12 06:53:20 GMT
FROM:    S. Bradley Cenko at Caltech  <cenko@srl.caltech.edu>

S. B. Cenko (UC Berkeley) reports on behalf of a larger collaboration:

We have imaged the field of GRB090812 (Stamatikos et al., GCN 9768) with
the automated Palomar 60 inch telescope.  Observations were obtained in
the Sloan r', i', and z' filters beginning at 6:34 UT (~ 2.5 minutes after
the burst).

Near the XRT afterglow we detect a point source at coordinates (J2000.0):

   RA: 23:32:48.55
   Dec: -10:36:17.0

with an estimated uncertainty of ~ 0.3" in each coordinate.  This is
consistent with the position reported by the UVOT.

We measure the following magnitudes for the source, calculated with
respect to the SDSS DR7:

Time (UT mid-point)  Exposure (s)   Filter       Magnitude
-----------------------------------------------------------------------
06:05:02             60             r'           16.18
06:06:27             60             i'           16.39
06:09:28             60             r'           17.30
06:10:43             60             i'           17.34

The fading nature confirms this is the afterglow of GRB090812.

Further observations are planned.