Low-resolution (LR-HK) squared visibilities of HR 4049 as a function of spatial frequency. Top to bottom: observed squared visibilities , model squared visibilities , and residual squared visibilities . Colors refer to the wavelength of the observation: from 1.6 μm (blue) to 2.4 μm (red). The gap visible for each observation is the band gap between the H and K bands. The H-band squared visibilities are higher than the K-band measurements because of the higher flux contribution of the unresolved primary star at short wavelengths.