Left: SED of a young stellar object. In blue: the stellar photosphere (represented as a black body) at 10 000 K; in red: the environment black body at 1500 K; and in black: the sum of the two contributions. The vertical color lines are the spectral channels of PIONIER. The two contributions cross in the H band. In the top right corner as a dashed line: the flux ratios of every component from the SED, as a full line: the result of modeling the fluxes with power laws. Right: in black, expected visibilities from the extended structure alone. In color: the star contribution has been added and colors follow the standard color code (blue: shortest wavelength, red: longest wavelength). The visibilities increase with shorter wavelengths because the stellar contribution is higher.