Bottom versus upper limit of the instability range. Models computed using the physical parameters from spectroscopy are plotted as red and green crosses. The limits of the frequencies with the highest amplitudes observed in HD 50870 are depicted with a blue star. The shaded yellow area shows where a theoretical model must be to predict an over-stable frequency range containing the observed one. The models with a Δν in the observed range of [3.5,4.5] d^-1 are marked as light blue squares.