TITLE: GCN CIRCULAR NUMBER: 13605 SUBJECT: GRB 120807A: TAROT La Silla observatory optical observations DATE: 12/08/07 14:39:04 GMT FROM: Alain Klotz at CESR-CNRS Klotz A. (IRAP-CNRS-OMP), Gendre B. (ASDC/INAF-OAR), Boer M. (UNS-CNRS-OCA), Atteia J.L. (IRAP-CNRS-OMP) report: We imaged the field of GRB 120807 detected by SWIFT (trigger 530267) with the TAROT robotic telescope (D=25cm) located at the European Southern Observatory, La Silla observatory, Chile. The observations started 31.5s after the GRB trigger (15.2s after the notice). The elevation of the field decreased from 8 degrees above horizon and weather conditions were poor (due to the low elevation). The first image is trailed with a duration of 60.0s (see the description in Klotz et al., 2006, A&A 451, L39). We do not detect any OT in the enhanced Swift-XRT position (Evans et al. GCNC 13603) with a limiting magnitude of: t0+31.5s to t0+91.5s : R > 15.5 Further images does not show OT anymore at about the same limiting magnitude until 1500 seconds after the trigger. Magnitudes were estimated with the nearby USNO-B1 stars and are not corrected for galactic dust extinction. N.B. Galactic coordinates are lon=333.3260 lat= +3.6420 and the galactic extinction in R band is about 4 magnitudes estimated from D. Schlegel et al. 1998ApJ...500..525S. This message may be cited.