Example of a partially resolved binary. Top left panel: c^* vs. G for the star DR3 2624130051834565504. The data are distributed around two clumps, one around c^* ≃ 0 and the second around c^* ≃ 0.315. Top right panel: G magnitude time series of the star Gaia DR3 2624130051834565504 and of its close neighbour, Gaia DR3 2624130051834223104. The two sources form a partially resolved binary; i.e. depending on the observation time and on the scan angle, the two stars can be resolved or unresolved in the astrometric instrument. Bottom left panel: G_BP and G_RP epoch spectra corresponding to the case in which the two stars are unresolved both by the astrometric and spectrophotometric instruments. In this case, c^* is close to 0 because both instruments collect the fluxes coming from the two stars. Bottom right panel: G_BP and G_RP epoch spectra corresponding to the case in which the stars are resolved in the astrometric field but blended in the G_BP and G_RP FoV. In this case, the source exhibits a strong excess factor because the astrometric instrument collects the flux coming from a single source whereas the spectrophotometric instrument collects the flux coming from the star and its neighbour. We note that the G_BP and G_RP epoch spectra are only shown here for illustration; they will be available to the community in Gaia DR4.