Radial profiles of the mean brightness of the photosphere-subtracted images. Each point of these curves was computed as the mean of the emission in an elliptical annulus centered on the peak of the main emission close to the image center. They correspond to an axisymmetric disk model inclined to 40° relative to the plane of the sky (see text). They are one pixel wide, i.e. 1 arcsec in the 70 and 100 μm images and 2 arcsec in the 160 μm image. The Gaussian with the FWHM of the beam is the profile expected for a hypothetical point source in the background aligned by chance with the star and shown for comparison.