TITLE: GCN CIRCULAR NUMBER: 7706 SUBJECT: GRB 080507: Keck photometry DATE: 08/05/10 02:33:56 GMT FROM: Daniel Perley at U.C. Berkeley D. A. Perley (UC Berkeley), J. X. Prochaska (UCO/Lick), and J. Hennawi (UCB) report: We imaged the field of Super-AGILE GRB 080507 (Lapshov et al., GCN 7697) with Keck I (+LRIS) during morning twilight starting at 15:03 UT on 2008-05-08 (31.3 hours after the trigger). Four exposures were taken in g and R filters simultaneously, although due to twilight only the first two R-band frames were usable. We detect the optical afterglow reported by Kann et al. (GCN 7701) at a position of: RA = 15:34:43.39 Dec = +56:26:08.28 (estimated uncertainty of 0.7") in R-band. Our magnitude, calibrated to seven USNO-B1.0 stars, is R = 22.20 +/- 0.11 at 1.31 days after the trigger. This supports the generally non-fading behavior between 1-2 days after burst in observations from the Swift UVOT (Breeveld et al., GCN 7702) and Tautenberg (Kann et al.). For reference, the observed magnitudes of two nearby USNO stars in the same calibration system are: 15:35:10.99 +56:23:57.02 R = 20.53 +/- 0.02 15:34:47.68 +56:25:16.44 R = 18.63 +/- 0.01