MATISSE high spectral resolution (R ∼ 1000) observation of the Be star α Arae. Comparison of the observation in the 4.053 μm Brα emission line (solid blue line) with the best-fit of a rotating disk toy model (red dashed line). Top: images of the toy model at different wavelengths in the continuum and through the line. Bottom: all observable quantities from a single MATISSE observation, including the normalised spectrum, the four closure phases, the six squared visibilities, and the six differential phases.