Fractional mass of the convective core for the eight stars that were found to have a convective core in this study. For each star, the open symbols correspond to the core size of the five models of the two grids (blue squares for Cesam2k models, red circles for mesa models) that yield the lowest values of χ² as defined by Eq. (7). The filled squares give the core sizes obtained from a Levenberg-Marquardt optimization and the evolution code Cesam2k (see Sect. 5.1).