Gravity-darkening coefficient β estimated from the ELR model (Espinosa Lara & Rieutord 2011) as a function of the rotation flattening ϵ compared with values measured from interferometric observations of six rapidly rotating stars (references in Sect. 5.4), Achernar (α Eri) being the flattest one. The estimate of β is obtained from a fit to the log T_eff versus log g_eff curves directly predicted by the ELR model, such as in Fig. 12 (right). The ELR model predictions and interferometric measurements have a good general agreement (see Sect. 5.4 for a more detailed discussion).