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We present a technique to extract radial velocity measurements from echellespectrograph observations of rapidly rotating stars ($V\sin{i} \gtrsim 50$ kms$^{-1}$). This type of measurement is difficult because the line widths ofsuch stars are often comparable to the width of a single echelle order. Tocompensate for the scarcity of lines and Doppler information content, we havedeveloped a process that forward-models the observations, fitting the radialvelocity shift of the star for all echelle orders simultaneously with theechelle blaze function. We use our technique to extract radial velocitymeasurements from a sample of rapidly rotating A- and B-type stars used ascalibrator stars observed by the California Planet Survey observations. Wemeasure absolute radial velocities with a precision ranging from 0.5-2.0 kms$^{-1}$ per epoch for more than 100 A- and B-type stars. In our sample of 10well-sampled stars with radial velocity scatter in excess of their measurementuncertainties, three of these are single-lined binaries with long observationalbaselines. From this subsample, we present detections of two previously unknownspectroscopic binaries and one known astrometric system. Our technique will beuseful in measuring or placing upper limits on the masses of sub-stellarcompanions discovered by wide-field transit surveys, and conducting futurespectroscopic binarity surveys and Galactic space-motion studies of massiveand/or young, rapidly-rotating stars.

Extracting Radial Velocities of A- and B-type Stars from Echelle Spectrograph Calibration Spectra