Bailey diagram in K_s band, showing amplitude vs. period, for our Cepheid candidate sample (red diamonds contoured in black) together with other well-known CCs (light green stars) and T2Cs (light blue open symbols). T2Cs are divided into the three main subtypes (see text). The open triangles, circles, and stars represent BL Her, W Vir, and RV Tau stars, respectively. Literature CCs come from the compilation by Inno et al. (2015) and T2Cs from Braga et al. (2018). The classification of this comparison sample is based on optical data, and is therefore more accurate than those based on near-IR data.