Photometry of the orbital cycle around orbital phase 0.5 for three DPVs: OGLE-LMC-DPV-074 (left panel), OGLE-LMC-DPV-033 (middle panel), and OGLE-LMC-DPV-062 (right panel). The dashed red and black lines represent the best polynomial fits to the data at the maximum and minimum phases of the long cycle, respectively. The solid lines correspond to 1000 bootstrap realisations that we used to estimate the uncertainty, and the shaded region indicates the resulting 1σ confidence interval (see details in Sect. 3.4). The quantity ΔA_II is derived using Eq. (1).