Upper: W1 magnitude versus orbital phase according to the ephemeris given by Eq. (2). Colors represent time intervals. Lower: color-color diagram for non-variable HIPPARCOS stars of spectral type B1 V – K3 V, Be stars, and DPVs according to Mennickent et al. (2016). The UU Cas data is added with colors along with numbers (in some cases) showing the orbital phases. Phase zero corresponds to the primary (deeper) eclipse.