CROSS-CORRELATION RADIAL-VELOCITY TECHNIQUES FOR ROTATING F-STARS

Data reduction techniques for cross-correlation determination of radial velocities for F stars using echelle spectra obtained with the Center for Astrophysics Digital Speedometers are described and evaluated. Synthetic spectra, calculated for a grid of spectral types and rotational velocities, are used to derive radial velocities for a large sample of nearby F stars with a wide range of rotational velocities. Using a grid of calculated spectra provides a set of noise-free templates on a consistent wavelength scale and allows a closer match between the rotational velocity of the object and that of the template spectrum than would be possible using observed spectra as templates. We describe the methods used to choose the template parameters for each star and the tests conducted to evaluate the accuracy of our procedure. Typically the random error of a single velocity measurement is in the range 0.7 to 3 km s-1, depending primarily on the rotation of the star. The zero point of our velocity system has been established to an accuracy of better than 1 km s-1 for the F stars.