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

Abstract

We study the Starobinsky or R-2 model of f(R) = R + alpha R-2 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 (rho) over bar = (kp) over bar gamma with (k) over bar similar to 5.0 and gamma similar to 0.75 and the constraint of alpha less than or similar to 1.47722 x 10(7) m(2), we obtain the minimal mass of the NS to be around 1.44 M circle dot. In addition, if (k) over bar is larger than 5.0, the mass and radius of the NS would be smaller.