Na I TLC from HARPS-N observations of MASCARA-2b for four bandwidths: 0.75 Å (first column), 1.5 Å (second column), 3.0 Å (third column), and 5.0 Å (fourth column). In all panels, the light gray dots indicate the values from all the spectra, and the black dots the same data binned with 0.003 phase step. First row: observed TLC of the Na I D lines from our data reduction. The relative flux of the D₁ and D₂ lines is averaged. The red line indicates the modeled TLC, which is the combination of the best-fit Na I absorption and the CLV and RM effects (Yan et al. 2017). This model is calculated theoretically and there is no fitting to the data. Second row: the CLV + RM effects. The black line indicates the result of removing the Na I absorption model from the observed TLC. The modeled CLV and RM effects are shown in red. Third row: the Na I absorption light curve obtained dividing the observed TLC by the modeled CLV + RM effects (black line). The red line is the best-fit Na I absorption model. Fourth row: residuals between the observed TLC and the model. We note the different y-scale of the panels.