PHOENIX Model Atmospheres

[zachway1996]

In order to compare Korg synthesized spectra of M dwarfs to the BT-Settl (CIFIST) models, it would be awesome to be able to build spectra from the PHOENIX model atmosphere grid.

Atmospheres: https://phoenix.astro.physik.uni-goettingen.de

Comparison between models for cool stars: https://iopscience.iop.org/article/10.1088/1742-6596/328/1/012005/pdf

[ajwheeler]

Some initial notes:
It looks like the atmospheres provide tau, T, P, rho, and Pe. The question is: which tau. Section 2.3 of the paper suggests that it is tau at 12,000 Å for Teff < 5000 K and tau at 5000 Å otherwise. If so, this will require only a very simple addition to Korg to make things work (the reference wavelength is currently fixed at 5000 Å, but making it configurable wouldn't be hard).