Position of the observed stars on the T–(150M − L) plane. Light blue circles with error bars show the stars from Table 2. The hatched area shows where the second overtone is excited. The different patterns indicate the different metallicites. The dotted, dashed, and solid black curves correspond to those models that have the ratio (f₂ − f₀)/f₀ = 0.686 for the linear grids with metallicities Z = 0.0001, Z = 0.003, and Z = 0.0011, respectively. The blue and the red solid curves are the first overtone blue and the fundamental red edges of the instability strip with M = 0.65 M_⊙ for reference as given by Marconi et al. (2015). Grey squares denote models with |2f₁ − f₀ − f₂|< 0.005 resonance.