Impact of continuum variations on FRs from close- (red) and wide-spaced (blue) wavelength components. Upper panel: 15 times the same ζ Gem spectrum as was used in Sect. 4.1 with varying continuum slopes (see color bar in lower panel). The missing part in the presented spectrum corresponds to HARPS’ chip gap. Middle panel: zoomed-in view of the region around ~ 5295 Å where the λ regions are highlighted by vertical spans. Lower panel: deduced T_{eff, FR} values as a function of the measured FRs at different continuum slopes. The models are represented by red and blue solid curves while dashed red and blue lines and filled circles of the same colors indicate the finding from the original spectrum without any modification of the continuum.