TITLE: GCN GRB OBSERVATION REPORT NUMBER: 2645 SUBJECT: GRB 040812: Keck and LCO optical observations DATE: 04/08/14 22:59:59 GMT FROM: Edo Berger at Caltech E. Berger (Carnegie Observatories), D.B. Fox, S.R. Kulkarni (Caltech), Wojtek Krzeminski and Mario Hamuy (Las Campanas Observatory, Carnegie) report on behalf of a larger collaboration: "We imaged the 2-arcmin error circle of GRB 040812 (GCN #2640) with the Low-Resolution Imaging Spectrometer on the Keck-I telescope 47 and 104 minutes after the burst, and with the Du Pont 2.5-m telescope at Las Campanas Observatory (LCO) 1.75 days after the burst. All observations were taken in the I-band (Galactic extinction, A_I~2.3 mag). Within the 8-arcsec radius error cirle of the VLA source detected by Soderberg (GCN #2643) we find several sources, but none exhibit significant variability either between the two Keck epochs or between the Keck and LCO observations. Visual comparison of the two Keck epochs do not reveal the presence of a strongly fading source within the entire 2-arcmin INTEGRAL error circle." This message may be cited