Analytic Polytropic Models

Setting the model_type parameter of the &model namelist group to 'ANAPOLY' tells the frontend to create an analytic polytropic stellar model. Because the structure of these model can be computed analytically, there is no need to read from an external file.

The n_poly parameter of the &model namelist group controls the polytropic index; valid choices are 0, 1 or 5. Likewise, the Gamma_1 parameter controls the first adiabatic index of the model, while the n, s and grid_type parameters control the model grid. See the Stellar Model Parameters section for further details.

It’s possible to create truncated polytropic models, with a finite surface pressure and density, by setting the theta_s to a value other than zero (this parameter represents the desired surface value of the polytropic dependent variable \(\theta\)). A non-zero theta_s is required when n_poly=5.