Reduced χ² map for the fit of a simple binary model to the squared visibility (left) and closure phase (right). The maps are given as a function of two free parameters: the semi-major axis of the companion’s orbit and the flux ratio between the putative companion and Vega. For each couple of semi-major axis/contrast, the orbital phase at a given time t₀ has been optimised to minimize the . All models corresponding to a semi-major axis larger than 2 AU in the closure phase map are beyond 5σ and are not shown for the sake of clarity.