Simultaneous photometric and RV monitoring of the transit of Qatar-2 b. Top panel: IAC80 photometric data. The black line is the model light curve, but it is not a fit to the data (see text in Sect. 4.3 for details). Middle panel: RV time-series covering the transit (red asterisks). To highlight the RM effect, the orbital RV trend was subtracted. Together with our best-fit model (black thick line), we also show models with VsinI_⋆ = 2.0 km s^-1  and λ = −90, 90, 180 deg (dashed blue, dot-dashed green, magenta lines, respectively). Bottom panel: RV residuals for the best-fit model of the RM effect and for the other three models shown in the middle panel.