TITLE:   GCN CIRCULAR
NUMBER:  6739
SUBJECT: GRB 070809: Keck Imaging
DATE:    07/08/10 11:11:05 GMT
FROM:    Daniel Perley at U.C. Berkeley  <dperley@astro.berkeley.edu>

D. A. Perley (UC Berkeley), C. C. Thoene (DARK, UCB), J. Cooke (UC 
Irvine), J. S. Bloom (UCB), and E. Barton (UCI) report:

Starting at 06:21:52 UT (2007-08-10), we imaged the field of GRB 070809 
(GCN 6728), a short or intermediate-duration (GCN 6732) burst, with the 
Keck I telescope (+LRIS).  We obtained under very high airmass (>2.6) 
and intervening cirrus 4x300 seconds of imaging in R band and 4x330 
seconds in g band.

At the edge of the refined XRT error circle (GCN 6737) we detect a 
single, faint source in both filters, with coordinates:

RA = 13:35:04.55
dec = -22:08:30.8
(err: 0.4")

Relative to the USNO B1.0 star at 13:35:09.80 -22:09:15.9 (R2=19.55) we 
measure a preliminary magnitude of R~24.0.  It is not possible to tell 
whether the object is fading, but it does not appear visibly extended.

We note also the presence of an edge-on galaxy near the error circle, at 
coordiates of 13:35:04.25, -22:08:26.8.

No other objects are present in or near the error circle to a limiting 
magnitude of R~25.5.

An image of the field is available at 
http://lyra.berkeley.edu/~dperley/070809/070809keckR.png .