Gravitational mass M vs. central baryon density n_c for non-rotating NS models based on the sets EOS.H (blue lines – H) and EOS.N_ref (black lines – N_ref). In N_ref: A is APR, B is BSk20, C is DH; in H: a is SA.BSR2, b indicates BM165, c indicates GM1Z0, d is UU1, e is G.TM1C. EOS labels from Table 1. Solid lines: stable NS configurations. Dotted lines: configurations unstable with respect to small radial perturbations. Vertical lines crossing the M(n_c) curves indicate configurations with n_c/n₀ = 2,3,.... Hatched strip correspond to M = 1.4 ± 0.05M_⊙, and the observational constraints for J1614-2230 and J0348+0432 are marked in blue and magenta, respectively (1-σ errors). (Colour online.)