GCN Circular 5539
J. Wren, W.T. Vestrand, P.R. Wozniak, R. White, S. Evans, and J. Pergande of Los Alamos National Laboratory report: The RAPTOR array of telescopes autonomously responded to Swift trigger 228316. Conditions were cloudy at our primary telescope site but our wide-field RAPTOR-B small telescope array, located at our secondary site, imaged the event under clear conditions. Imaging began at 08:34:12.53 UTC (86.0 s after the trigger, 5.8 s after receipt). We do not detect the counterpart seen by the Swift XRT (Racusin et al. GCN 5528) and P60 (Cenko et al. GCN 5529). The initial unfiltered 5 s exposure yields a 3-sigma limiting magnitude at the counterpart location of R=15.2 when calibrated against the GSC 1.1 R-band. This limit has not been corrected for foreground galactic extinction.