Polytropic models represent stars in hydrostatic equilibrium that follow the polytropic equation of state,
for piecewise-constant \(K\) and polytropic index \(n\). The formalism behind these models is described in the Composite Polytropes section. The build_poly executable can be used to create a polytropic model and write it to a file in POLY format.
To use a polytropic model with GYRE, set the
parameter in the
&model namelist group to
file parameter to the name of the POLY file.