HARPS observations of nine galactic Cepheids

For each star, we derive an interpolated cross-correlated radial velocity curve using the HARPS pipeline. Pulsating phases and HARPS radial velocity measurements can be found in Table 1.

The cross correlation method is widely used to derive the radial velocity curve of Cepheids when the signal to noise ratio of the spectra is low. However, if it is used with an inac curate projection factor, it might introduce some biases in the Baade-Wesselink (BW) methods of determining the distance of Cepheids. In addition, it might affect the average value of the radial velocity curve (or gamma-velocity) important for Galactic structure studies.