GCN Circular 6084
J. Wren, W.T. Vestrand, P.R. Wozniak, R. White, J. Pergande of Los Alamos National Laboratory report: Our Raptor-S telescope responded to Swift trigger 259714 (Sato et al., GCN 6074) at 09:11:17.10 UT, 42.8 s after the trigger and 6.3 s after receiving the GCN packet. We clearly detect the source at the location of the optical counterpart identified by Guidorzi et al. (GCN 6077). Our first 5 second exposure was obtained while the Swift BAT was still detecting emission from the second GRB pulse (Markwardt et al., GCN 6081). Our measurements show that the optical counterpart brightened from fainter than magnitude 18.7 to 18.2 in the first 300 seconds after the trigger time and then began to fade steadily after that. Our unfiltered magnitudes were calibrated using the R-band magnitudes from the USNO B1.0 catalog.