LMC RV Tauri stars with different SED characteristic, plotted in the HRD. The black lines are evolutionary tracks for a 1 M_⊙, 2 M_⊙, ³ M_⊙, and 4 M_⊙ stars with a composition of Z = 0.008 and Y = 0.26 for the LMC (Bertelli et al. 2009). The dashed lines are post-AGB tracks from Miller Bertolami (2016) for 1 M_⊙, 1.25 M_⊙, 2 M_⊙, and 3 M_⊙ initial mass stars with an initial metallicity of Z = 0.001. The blue line represents the evolution of a 3 M_⊙ star, which goes through a blue-loop phase. The slanted dotted lines show the theoretical instability strip taken from Kiss et al. (2007). The four points with cyan marker edges indicate the position of OGLE-LMC-T2CEP-119, OGLE-LMC-T2CEP-149, OGLE-LMC-T2CEP-190, and OGLE-LMC-T2CEP-191, which display clear period change in their (O−C) diagram. The stars in the grey circles denote the position of OGLE-LMC-T2CEP-005 and OGLE-LMC-T2CEP-199, which have higher-than-expected luminosities (see Sect. 7.5). The tip of the RGB for each track corresponding to a mean metallicity of the LMC are indicated with orange “+” signs, which are at L ∼ 3150, 330, 630, and 1450 L_⊙ for the 1, 2, 3, and 4 M_⊙ tracks, respectively. The upper and lower horizontal dotted lines indicate the tip of the RGB for a 1 and 4 M_⊙ star, respectively. The cyan “x” markers represent the start of the early AGB phase (E-AGB); these markers are at L ∼ 170, 370 and 1090 L_⊙ for the 2, 3 and 4 M_⊙ tracks, respectively.