Results of the Hα line analysis of MASCARA-2b. Each column corresponds to one night. First row,top: residuals after dividing each spectrum by the master-out spectrum. Second row: best-fit model describing the first panel residuals, including absorption, CLV and RME. Third row: residuals after subtracting the best-fit model (second row) to the data (first row). Fourth row: transmission spectrum obtained when combining the in-transit residuals from fourth row in the planetary rest frame. The black dots show the transmission spectrum binned in 0.2 Å intervals and the propagated errors from the photon noise. Light blue shows the standard deviation of the residuals from fourth row. The red lines show the Gaussian profile derived from the best-fit parameters of second row. Fifth row: residuals after subtracting the Gaussian profile to the transmission spectrum. In all cases the residuals (rows from 1st to 3rd) are binned in intervals of 0.002 in orbital phase and 0.05 Å in wavelength. The relative flux (F_in /F_out −1) in % is shown in the colour bar. In white we show the time regions for which we have no information. The horizontal lines show the first and last contact times of the transit.