TITLE: GCN CIRCULAR NUMBER: 12878 SUBJECT: GRB 120119A: SMARTS optical/IR afterglow observations DATE: 12/01/19 19:46:55 GMT FROM: Bethany Cobb at GWU B. E. Cobb (GWU), reports: Using the ANDICAM instrument on the 1.3m telescope at CTIO, we obtained optical/IR imaging of the error region of GRB 120119A (GCN 12859, Beardmore et al.) over several epochs, starting ~0.6 hours post-burst. For the first epoch, several dithered images were obtained in each filter, with total summed exposure times of 180s in each of BRIJK and 120s in each of H and V. For later epochs, total summed exposure times amounted to 15 minutes in I and V and 12 minutes in J and K. At a mid-exposure time of 2012-01-19 04:43 UT (0.64 hrs post-burst), the GRB afterglow (e.g. GCN 12859, Beardmore et al., GCN 12860, Morgan et al., GCN 12863, Schady et al.) is detected with the following magnitudes: B = 20.07 +/- 0.06 V = 18.91 +/- 0.05 R = 18.02 +/- 0.03 I = 16.96 +/- 0.03 J = 15.14 +/- 0.05 H = 14.02 +/- 0.06 K = 12.89 +/- 0.10 Between about 0.6 hrs and 3 hrs post-burst, the GRB afterglow fades with a decay rate of approximately alpha = 1.6 (where afterglow flux is proportional to t^-alpha). time post-burst I-band magnitude 0.64 hrs 16.96 +/- 0.03 1.71 hrs 18.52 +/- 0.03 2.97 hrs 19.39 +/- 0.05 (Optical photometry is calibrated against Landolt standard stars and IR photometry is calibrated against 2MASS stars in the field.)