TITLE: GCN CIRCULAR NUMBER: 12883 SUBJECT: GRB 120119A: TAROT La Silla observatory optical observations DATE: 12/01/20 09:47:40 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 120119A detected by SWIFT (trigger 512035) with the TAROT robotic telescope (D=25cm) located at the European Southern Observatory, La Silla observatory, Chile. The observations started 33.0s after the GRB trigger (9.2s after the notice) using the trigger time origin at 04:04:30.21 UT (Beardmore et al. GCNC 12859). The elevation of the field increased from 67 degrees above horizon and weather conditions were good. We observed during 4.35h until the dawn allowing a continuous follow up of the afterglow discovered by Beardmore et al. (GCNC 12859). The first image is trailed with a duration of 60.0s (see the description in Klotz et al., 2006, A&A 451, L39). This image was obtained during the fading of the gamma emission. We extracted three measurements from the trail. A first magnitude extraction is reported in the following table. As noticed by LaCluyze et al. (GCNC 12864), the optical emission decreased slowly in the range 33s to 200s, then it increased to reach a maximum R=16.8 at 850 +/- 50s. A decay phase alpha=1.3 occured between 10^3 and 10^4 seconds. As noticed by Elenin et al. (GCNC 12871) the begining of a plateau is suspected after 10^4 seconds. The end of the night over Chile does not allow to conclude definitively. Note that the GRB was also observed at TAROT Calern (France) but data are poor due to the low elevation of the field. However, the afterglow is also detected in the TAROT Calern images. ------------------------------------------ t1(min) t2(min) mag dmag ------------------------------------------ 0.55 0.85 16.96 0.30 0.85 1.15 17.15 0.30 1.15 1.55 17.05 0.30 1.67 2.17 17.32 0.16 2.34 2.84 17.37 0.12 3.01 3.51 17.58 0.22 3.67 4.17 17.53 0.17 4.34 4.84 17.27 0.17 10.36 11.86 17.02 0.26 12.03 13.53 16.87 0.20 13.70 15.20 17.03 0.15 15.37 16.87 16.94 0.18 17.03 18.53 17.19 0.29 18.70 20.20 17.19 0.11 21.31 22.81 17.27 0.24 22.97 24.47 17.37 0.16 24.64 26.14 17.35 0.09 26.31 27.81 17.32 0.19 27.98 29.48 17.40 0.06 29.64 31.14 17.59 0.05 35.98 38.98 17.65 0.05 39.15 42.15 18.00 0.21 45.48 48.48 18.09 0.06 48.65 51.65 18.31 0.25 55.66 58.66 18.39 0.15 58.83 61.83 18.58 0.26 42.32 84.94 18.51 0.12 65.16 91.28 19.10 0.15 95.40 126.40 19.51 0.09 129.73 195.34 19.78 0.12 199.45 261.71 19.90 0.08