Polytropic Models

Polytropic models represent stars in hydrostatic equilibrium that follow the polytropic equation of state,

\[p = K \rho^{(\npoly+1)/\npoly},\]

for piecewise-constant \(K\) and polytropic index \(\npoly\). The structure of polytropic models is obtained by solving the Lane-Emden equation; GYRE doesn’t do this itself, but can read structure data from external files created by the build_poly executable (see the Building Polytropic Structure Files appendix for more details).

To use a polytropic model with GYRE, set the model_type parameter in the &model namelist group to 'POLY', and the file parameter to the name of the polytropic structure file.