DoLP radial extension in R_⋆, taken as the radial range over which the cumulative DoLP lies between 10 and 95% of its maximum, as a function of the star distance. The RSGs are in red, and the AGB stars are in blue. The gray squares correspond to the PSF calibrator half width at half maximum (in units of R_⋆) at the distance of each star. The gray diamonds with an error bar correspond to the position and extent of the AO ring of SPHERE. We used the filter at the shortest wavelength observed for each star.