Stellar relaxation
==================


When mapping 1D profile from MESA to a 3D code such as Phantom, a relaxation procedure is required to ensure that the particles are in hydrostatic equilibrium.

In phantom this is achieved by a process called ``relax-o-matic``
(`Lau et al., 2022 <https://doi.org/10.1093/mnras/stac049>`_ - **please see its appendix C for full details of how it works**).


To run ``relax-o-matic`` after setting up a star,
just follow the instructions during setup (from ``phantomsetup``) and type ``yes`` when prompted "Relax star automatically during setup?";

Then, modify the ``.setup`` file and fill in the relaxation options, which are pretty self-explanatory::

	relax_star        =           T    ! relax star automatically during setup
	tol_ekin          =   1.000E-07    ! tolerance on ekin/epot to stop relaxation
	tol_dens          =       1.000    ! % error in density to stop relaxation
	maxits            =        1000    ! maximum number of relaxation iterations
	write_rho_to_file =           F    ! write density profile to file

Run the ``phantomsetup`` again to start the auto relaxation process.
You are now good to go!

If interruptted during the relaxation, run ``phantomsetup`` again and it will pick up from where it left off automatically.

If in doubt, you can always run the star in isolation for a few years to see if relaxation procedure worked.