Transmission spectrum of MASCARA-1b around single lines, after combining the two nights of observation. In grey we show the original sampling of the data and in black the data binned by 0.1 Å. The width of the vertical light blue region indicates the uncertainty of υ_sys, that is, the position where the signals from the exoplanet atmosphere are expected (we note that the Li I is a doublet). The estimated models describing the RM and CLV effects on the transmission spectrum and their 1er and 3σ uncertainties are shown in violet.