Decomposition of Stokes I and V for R Aql (spectral resolution of 0.139 km s⁻¹). Left: Stokes I data are shown in black, and the global fit is shown in red. The vertical dashed colored lines are the positions of the center of the individual Gaussian functions used in the fit, plotted in various colors. Right: Stokes V data cleaned from instrumental polarization are shown in black (Sect. 3.2), and the fit is shown in red. The vertical dashed colored lines show the individual Gaussian I components from the Stokes I fitting procedure (left panel).