GCN Circular 4474
P.R. Wozniak, W.T. Vestrand, J. Wren, R. White, S. Evans of Los Alamos National Laboratory report: Our autonomous Raptor-S telescope responded to Swift trigger 176702 (Zane et al. GCN 4463) at 08:01:42.42 UT (6.8 seconds after receiving the trigger). We clearly detect a fading optical source at the location of the IR counterpart identified by Bloom et al. (GCN 4471). The measurements show that the optical counterpart faded from magnitude R=16.1+/-0.1 (5-second exposure) to about 17.5 over the first ten minutes. Our unfiltered magnitudes were calibrated using R2 magnitudes of the field sources in USNO B1.0 catalog.