Top panels: correlation coefficients for cross-correlation with the TiO template (VMR = 10^-7) between 640 nm and 670 nm, with and without injecting the template into the data prior to cross-correlation (middle and left panel, dashed and solid lines respectively). Restricting the wavelength range has reduced the S/N at which this template is retrieved after injection by over 9σ (compare to Fig. 5), but it is not clear to what extent persistent inaccuracies still adversely affect the sensitivity of this restricted template. Bottom row: correlation coefficients for cross-correlation Barnard’s star’s optical spectrum. No enhanced correlation is observed. Given that the injection of the stellar absorption spectrum into the planetary transmission spectrum is not physically meaningful, the sensitivity of this non-detection can’t straightforwardly be expressed in physical quantities like the limiting VMR.