M(R) dependence for the exact solution of the TOV equations obtained using a unified EOS and the approximate approach for the DH EOS. Different values of n_cc are used (from left to right; 0.16, 0.13, 0.11, 0.09, 0.077 fm^-3, see Table 1 for details). The value n_cc = 0.077 fm^-3 corresponds to the “real” crust-core boundary for the DH model. The solid blue curves show the M(R_core) relation, the dashed red curves show the M(R) approximation based on Eqs. (11), (12), and the black curve shows the exact solution of the TOV equation.