As Fig. 1 for R Leo. The six different epochs are denoted by the symbols and colours as indicated in the top left panel. No fits are indicated for the individual epochs in the temperature vs. radius (top right panel). The long-dashed line indicates the grey atmosphere temperature profile with a temperature at R_* of T = 2850 K. In the bottom left, the lines indicate the maximum and minimum power-law fit to the size vs. frequency relation when correcting each epoch for the observed expansion (Sect. 5.2). In the uv plot only two epochs, one for each observing band, are indicated for illustration.