Simulated model visibility curves. Three ring models with different power law values are shown as full lines (see the legend for the colour coding). The inner and outer ring radii are fixed to the values adopted for the 89 Her system. The correlated flux at zero baseline (i.e., the total flux) is fixed at 100 Jy for comparison purposes. For each ring model, the uniform disk model that crosses the correlated flux curve at 40 Jy is shown for comparison. The black dashed line represents the asymptotic limit of the ring model: an infinitesimally thin ring at the sublimation radius.