Section of the X-shooter spectrum for one of the observed Cepheid candidates (B06). Top: observed spectrum (light blue) with the best-fit telluric model (red dot-dashed line). This spectral region is particularly affected by telluric absorption. Bottom: final telluric-corrected spectrum (green) together with its corresponding best-fit synthetic spectrum (magenta dashed line). The most prominent absorption lines are marked and labeled. The gray shaded regions were excluded from the spectral fitting procedure due to the large residuals in the telluric correction process of these heavily affected spectral regions (see Sect. 7 for more details about the atmospheric parameter determination).