TITLE: GCN CIRCULAR NUMBER: 19001 SUBJECT: GRB 151215A: TAROT Calern observatory very early optical detection DATE: 16/02/07 22:36:40 GMT FROM: Alain Klotz at IRAP-CNRS-OMP Klotz A., Turpin D., Atteia J.L. (CNRS-OMP-IRAP), Boer, M., Laugier, R. (CNRS-ARTEMIS), Gendre B. (UVI - Etelman Obs.) report: We imaged the field of GRB 151215A detected by SWIFT (trigger 667392) with the TAROT robotic telescope (D=25cm) located at the Calern observatory, France. The observations started 31.6s after the GRB trigger (17.7s after the notice). The elevation of the field decreased from 56 degrees above horizon and weather conditions were good but images were slightly unfocused. The first image is trailed with a duration of 60.0s (see the description in Klotz et al., 2006, A&A 451, L39). Due to the unfocused condition, we took time to reprocess the image to extract the magnitude of the optical transient discovered by Cenko et al. (GCNC 18692): t1(s) t2(s) Rmag d_Rmag 31.6 44.5 17.3 0.5 44.5 91.6 16.7 0.3 Magnitudes were estimated with the nearby USNO-B1 stars and are not corrected for galactic dust extinction.