Best geometric model fit (uniform disk + elliptical Gaussian; purple) to the SAM/NACO data (gray; as in Fig. 3). The fitting results are given in the legend. The spread of the values at similar baseline lengths is due to the different baseline position angles. 2.30 μm and 3.74 μm data in the upper and lower panel. Overplotted for comparison are the best fits of simpler, centrosymmetric functions, i.e., a uniform disk (green; lower line) and a circular Gaussian distribution (blue; middle dashed-line). The diameters (θ_UD) and FWHM of these fits are upper panel 223 and 102 mas, and lower panel 180 and 99 mas.