TITLE: GCN CIRCULAR NUMBER: 14476 SUBJECT: GRB 130427A: RAPTOR Bright Counterpart Before Swift Trigger DATE: 13/04/28 00:12:42 GMT FROM: James Wren at LANL J. Wren, W.T. Vestrand, P. Wozniak, and H. Davis, of Los Alamos National Laboratory report: Three RAPTOR full-sky persistent monitors at Maui, HI, and Los Alamos, NM, independently detected bright optical emission at the location of the Swift trigger 554620 (Maselli, et al., GCN 14448). Starting at 07:47:07.28 UT (50.2 seconds before the Swift trigger) we detect a brightening counterpart which peaks at magnitude R~7.4. After the peak, the source fades to below 10th magnitude at approximately the Swift trigger time. The unfiltered images from all three monitors are calibrated to the Tycho-2 V-band catalog.