Measured (center column) versus Monte Carlo simulations of the closure measured by the VLTI configurations of (left) thermal variations across the photosphere with temperature gradients ±100 K, and (right) a binary enshrouded in a large dust cloud with a temperature between 1000–1500 K and a radius up to 26% the diameter of the primary. Monte Carlo simulations assume a fixed zenith target geometry without Earth rotation synthesis. The light gray shaded region highlights ±1σ envelope of wavelength binned closure phases across the different MC simulations. Gray colors in the center column are measurements with uncertainties.