Equation-of-state of neutron stars with junction conditions in the Starobinsky model

We study the Starobinsky or R2 model of f(R) = R + αR2 for neutron stars with the structure equations represented by the coupled differential equations and the polytropic type of the matter equation-of-state (EoS). The junction conditions of f(R) gravity are used as the boundary conditions to match the Schwarzchild solution at the surface of the star. Based on these the conditions, we demonstrate that the coupled differential equations can be solved directly. In particular, from the dimensionless EoS δ= kpγ with k5.0 and γ0.75 and the constraint of α1.47722 × 107m2, we obtain the minimal mass of the NS to be around 1.44 M. In addition, if k is larger than 5.0, the mass and radius of the NS would be smaller.