Regular central expansion of the TOV equations
= Regular central expansion of the TOV equations
{title2=$m=\frac{4\pi}3\rho_cr^3+O(r^5)$}
For a smooth centre with density $\rho_c$ and pressure $p_c$, the <Tolman–Oppenheimer–Volkoff equation> gives $m(r)=4\pi\rho_cr^3/3+O(r^5)$ and $p(r)=p_c-2\pi(\rho_c+p_c)(\rho_c/3+p_c)r^2+O(r^4)$. A fixed <barotropic stellar equation of state> leaves one physical central parameter; the additive lapse constant fixes time normalization.