[vsnet-grb-info 9604] GRB 100807A: P60 Optical Afterglow Discovery

[GCN Circulars]

TITLE:   GCN CIRCULAR
NUMBER:  11073
SUBJECT: GRB 100807A: P60 Optical Afterglow Discovery
DATE:    10/08/07 20:55:56 GMT
FROM:    S. Bradley Cenko at Caltech  <cenko at srl.caltech.edu>

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

We have imaged the field of GRB 100807A (Grupe et al., GCN 11067) with the
automated Palomar 60 inch telescope.  Observations were obtained in the
Sloan r', i', and z' filters beginning at 9:16 UT on 7 August (~ 3 min
after the Swift trigger).

At the edge of the enhanced XRT position (Osborne et al., GCN 11070), we
detect a fading point source with coordinates (J2000.0):

	RA: 03:41:12.43    Dec: +67:40:17.4

Using several nearby objects in the USNO-B1 catalog for reference, we
report the following photometry for this object:

UT (mid-point)	t_burst (min)	Filter		Magnitude
---------------------------------------------------------------
09:16:55	3.7		R		20.47 +/- 0.17
09:18:21	5.1		I		19.80 +/- 0.14
09:47:07	33.9		R		21.57 +/- 0.20
09:49:58	36.8		I		20.96 +/- 0.20

The above magnitudes have not been corrected for the large Galactic
extinction along the line of sight.

The fading behavior confirms this source is the optical afterglow of GRB
100807A.