TITLE: GCN CIRCULAR NUMBER: 16967 SUBJECT: GRB 141026A: Skynet PROMPT-CTIO/Yerkes-41 Observations DATE: 14/10/27 20:26:34 GMT FROM: Adam S. Trotter at UNC-Chapel Hill/PROMPT/Skynet A. Trotter, J. Haislip, D. Reichart, V. Hoette, K. Cudworth, D. Harper, R. Kron, T. Linder, R. Russell, E. Struble, A. Aji, R. Beauchemin, T. Berger, A. Dow, A. Foster, N. Frank, M. Hinckle, K. Ivarsen, A. LaCluyze, M. Maples, J. Moore, M. Nysewander, C. Salemi, L. Zbinden, and J. A. Crain report: Skynet observed the Swift BAT/XRT localization of GRB 141026A (Hagen et al., GCN 16950, Swift trigger=616502) with one 24" telescope (PROMPT 8; I band) and four 16" telescopes (PROMPT 3,1,4,5; BVRI bands) of the PROMPT array at CTIO, Chile, and with the 41" telescope of Yerkes Observatory in Wisconsin, USA (g'r'i' bands). Starting at 2014-10-26 02:38:30 UT and continuing until 03:03 UT (t=1.5-26m post-trigger), Skynet took a total of 89 exposures ranging from 10s-160s each. We stacked subsets of these images to maximize the S/N ratio, and detected no optical source in any band at the OT position first reported by RATIR (Littlejohns et al., GCN 16952), and confirmed in later notices. Our 3-sigma limiting magnitudes are: ================================== tmid scope expos fil limit ================================== 10m PROMPT3 4x80s B >19.9 20m PROMPT1 4x160s V >20.4 19m PROMPT4 3x160s R >19.8 17m PROMPT5 4x80s I >19.9 4X160s 17m PROMPT8 12x80s I >20.0 63m Yerkes 1x80s g' >21.2 2x160s 60m Yerkes 2x80s r' >20.9 1x160s 66m Yerkes 1x80s i' >20.5 1x160s ================================== BVRI magnitudes are in the Vega System, and g'r'i' magnitudes are in the AB system, calibrated to 4 APASS stars in the field. Magnitudes have not been corrected for line-of-sight Milky Way dust extinction, with expected E(B-V)=0.16 (Schlafly & Finkbeiner 2011). No further Skynet observations are scheduled.