Relation between the radius and the mass of HD 52265, as inferred from model optimization. Colours are for optimized models of case 7 of Table 3 for different input physics, as listed in Table 2. Models for case 6 are plotted in grey, other cases are shown with open blue symbols. Bold solid horizontal and vertical black lines represent the values of the mass and radius derived from the scaling relations (Sect. 2.2.2). The corresponding uncertainties are displayed with dashed lines. The radius obtained using the Stefan-Boltzmann relation (Sect. 2.1) is shown as a triple-dot dashed line. Three groups of models lie on the Stefan-Boltzmann line: case 1, 4, and 5 models, as discussed in the text.