Response of the Neutron Star Properties to the Equation of State at Low Density

Using the RMF theory to describe the neutron liquid region in the neutron star and the Fermi gas model or FMT, BPS, and BBP model to describe the crust of the neutron star (referred as Fermi gas + RMF and RMF* respectively), the properties of the neutron star are calculated and compared with those from the RMF theory. Although the EOS at low density has negligible influence on the maximum mass of the neutron star, and its corresponding central density, energy density, and pressure, it changes the mass-radius relationship of neutron stars considerably. The differences of the neutron star radius corresponding to maximum mass between the RMF theory and RMF* calculations are 0.23-0.33 km.