摘要：Context.Accurate radial velocities (vrad) of Cepheids are mandatory within the context of Cepheid distance measurements using the Baade-Wesselink technique. The most commonvradderivation method consists in cross-correlating the observed stellar spectra with a binary template and measuring a velocity on the resulting mean profile. Nevertheless, for Cepheids and other pulsating stars, the spectral lines selected within the template as well as the way of fitting the cross-correlation function (CCF) have a direct and significant impact on the measuredvrad.Aims.Our first aim is to detail the steps to compute consistent CCFs andvradof Cepheids. Next, this study aims at characterising the impact of Cepheid spectral properties andvradcomputation methods on the resulting line profiles andvradtime series.Methods.We collected more than 3900 high-resolution spectra from seven different spectrographs of 64 Classical Milky Way (MW) Cepheids. These spectra were normalised and standardised using a single custom-made process on pre-defined wavelength ranges. We built six tailored correlation templates selecting unblended spectral lines of different depths based on a synthetic Cepheid spectrum, on three different wavelength ranges from 3900 to 8000 Å. Each observed spectrum was cross-correlated with these templates to build the corresponding CCFs, adopted as the proxy for the spectrum mean line profile. We derived a set of line profile observables as well as three differentvradmeasurements from each CCF and two custom proxies for the CCF quality and amount of signal.Results.This study presents a large catalogue of consistent Cepheid CCFs andvradtime series. It confirms that each step of the process has a significant impact on the deducedvrad: the wavelength, the template line depth and width, and thevradcomputation method. The way towards more robust Cepheidvradtime series seems to go through steps that minimise the asymmetry of the line profile and its impact on thevrad. Centroid or first-momentvrad, that exhibit slightly smaller amplitudes but significantly smaller scatter than Gaussian or biGaussianvrad, should therefore be favoured. Stronger or deeper spectral lines also tend to be less asymmetric and lead to more robustvradthan weaker lines.
