Echo Tomography of Sco X-1 using Bowen Fluorescence Lines
  We present preliminary results of a simultaneous X-ray/optical campaign of the prototypical LMXB Sco X-1 at 1-10 Hz time resolution. Lightcurves of the high excitation Bowen/HeII emission lines were obtained through narrow interference filters with ULTRACAM, and these were cross-correlated with X-ray lightcurves. We find evidence for correlated variability, in particular when Sco X-1 enters the Flaring Branch. The Bowen/HeII lightcurves lag the X-ray lightcurves with a light travel time which is consistent with reprocessing in the companion star. 
J. Casares (1), T. Mu\~noz-Darias (1), I.G. Martinez-Pais (1), R.   Cornelisse (2), P.A. Charles (2,3), T.R. Marsh (4), V.S....