Examples of CSE models with a Gaussian brightness intensity distribution in the case of (a) β Dor (1.86 mas) and (b) U Car (0.80 mas). The examples illustrate the difficulty of resolving a compact CSE with MATISSE/VLTI. For a CSE flux contribution of 5% of the total flux, compact CSEs between 5 and 10 R_⋆ cannot be resolved (see the green, orange, and red models). The large and bright model shown as the dashed magenta line is excluded in both stars, however. The upper limits for different CSE models are given in Table 5.