TITLE: GCN CIRCULAR NUMBER: 14445 SUBJECT: GRB 130420A: Continued Skynet/GORT Observations/Detections DATE: 13/04/25 22:19:25 GMT FROM: Adam S. Trotter at UNC-Chapel Hill/PROMPT/Skynet A. Trotter, N. Frank, A. LaCluyze, D. Reichart, K. McLin, L. Cominsky, T. Berger, H. T. Cromartie, R. Egger, A. Foster, J. Haislip, K. Ivarsen, M. Maples, J. Moore, M. Nysewander, E. Speckhard, and J. A. Crain report: Skynet continued observing the field of GRB 130420A (Page et al., GCN 14406, Swift trigger #553977) with the 14" GLAST Optical Robotic Telescope (GORT) at the Hume Observatory in California. It took 214 80-s exposures in Ic at times t=20.48-23.30h and t=26.25-28.56h after burst trigger, and 96 80-s exposures in Rc at t=23.33-26.15h. We performed photometry on the stacked exposures in each band, calibrated to six SDSS stars in the field. We detect the afterglow in both Ic and Rc bands at t~24h: band exp length mean time since trig mag(Vega) Ic 4.76h 24.37h 21.04 (+0.43,-0.31) Rc 2.47h 24.77h 21.00 (+0.25,-0.21) As we note in Trotter et al. (GCN 14427), and as Elenin et al. (GCN 14428) confirm, the afterglow exhibits a rising light curve at early times, peaking at t=330s (peak Rc~16, Ic~15.5). After the peak, the light curve fades with a power law index alpha~-0.9. A preliminary light curve of the first and second nights' data is at: http://skynet.unc.edu/grb/grb130420a_2.png