SMC 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 = 0.004 and Y = 0.26 for the SMC (Bertelli et al. 2009). The dashed lines are post-AGB tracks from Miller Bertolami (2016) for 1 M_⊙ and 1.5 M_⊙ stars and Z = 0.001, plotted as 2nd and 3rd from bottom, respectively. The bottom-most dashed track is for a 1 M_⊙ star with a metallicity of Z = 0.01, which is at a lower luminosity than a post-AGB track 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 tip of the RGB for each track corresponding to a mean metallicity of the SMC are indicated with orange “+” signs , which are at L ∼ 2880, 330, 660, and 1560 L_⊙ for the 1, 2, 3, and 4 M_⊙ tracks, respectively. The cyan “x” markers represent the start of the early AGB phase (E-AGB), which are at L ∼ 170, 510, and 1380 L_⊙ for the 2, 3, and 4 M_⊙ tracks, respectively. The stars in the grey circle are the OGLE-SMC-T2CEP-07 and OGLE-SMC-T2CEP-29, which shows ellipsoidal variability and eclipses in their light curves, respectively. The upper and lower horizontal dotted lines indicate the tip of the RGB for a 1 and 4 M_⊙ star, respectively