The mass-radius relations for several equations of state of neutron and strange stars matter are shown by dotted curves. The M–R relations for constant log g = 14.0,14.3,14.6 are shown by solid curves and the lines of constant redshift (z = 0.18,0.27,0.42 corresponding to the chosen log g for M = 1.4   M_⊙) by dashed curves. The upper-left region is excluded by constraints from the causality requirements (Haensel et al. 2007; Lattimer & Prakash 2007). The hatched horizontal belt marks the spread of pulsars masses accurately measured in double NS binaries (Haensel et al. 2007).