The black filled circles show the normalized flux from the star plus Haumea, as observed from the Asiago station, which is the one that provided the highest signal-to-noise ratio and enough time resolution to look for a faint atmosphere. They combine ingress and egress data and are plotted against the distance perpendicular to the local Haumea limb, as given by the solution shown in Fig. 2. The horizontal bars associated with each data point indicate the distance interval corresponding to the integration times of each point. The red line shows an example light curve obtained with an isothermal N₂ atmosphere at T = 40 K and with surface pressure p_surf = 15 nbar (at 3σ-level upper limit for better illustration, because the 1σ-level of 3 nbar would be difficult to notice). The red open circles show the expected flux at each data point after convolution with the finite integration point.