Canopus calibrated squared visibilities, V² (log scale), closure phases, CP, and errors as a function of the spatial frequency, observed with AMBER/VLTI (light blue) in the H (a) and K (b) bands. The red squares correspond to the best-fit-model observables obtained from an MCMC fit on the AMBER data using a power-law LD and including bandwidth smearing. The residuals of the fit are also shown.