TITLE: GCN CIRCULAR NUMBER: 17590 SUBJECT: GRB 150314A: Early RAPTOR Detection DATE: 15/03/17 00:43:21 GMT FROM: James Wren at LANL J. Wren, W.T. Vestrand, P. Wozniak, and H. Davis, of Los Alamos National Laboratory report: The RAPTOR network of robotic optical telescopes made observations of Swift trigger 634795 (Hagen, et al., GCN 17573). Our narrow-field instruments located in Los Alamos, NM, USA, arrived on target at 04:55:20.83 UT, T+27.98 seconds after the BAT trigger time. Our initial 5s exposure shows the counterpart (Zheng, et al., GCN 17574) at an unfiltered magnitude of 13.11 +- 0.02. The source fades steadily, reaching magnitude 15.87 +- 0.09 at T+180.38 s, in agreement with the KAIT lightcurve (Zheng, et al., GCN 17585). We derive a power-law decay slope of -1.50 using 04:54:52.86 as the BAT T0. Our unfiltered magnitudes were calibrated to the USNO-B1 R-band catalog. The optical counterpart is not detected in any of our persistent wide-field monitors during the gamma-ray emitting interval. Typical 3-sigma unfiltered limiting magnitudes during this period were V~9.8 based on comparison to the Tycho-2 V-band catalog.