Adding Atmosphere Models

Stellar atmosphere grids are implemented in SPISEA using STSci’s pysynphot and CDBS infrastructure. Adding a new atmosphere grid involves saving the models in a new sub-directory under your PYSYN_CDBS directory and creating a new function in atmospheres.py to access those files.

We’d recommend looking at the existing atmosphere model directories as a template for how to make a new one. Some general notes:

• The new atmosphere grid you implement should be placed in the <SPISEA_MODELS>/cdbs/grid/ directory

• Inside the new directory you need two things: a catalog.fits file (which tells SPISEA the Teff, logg, and metallicity of the atmospheres in your grid) and then the atmosphere model files themselves.

• The catalog.fits file MUST follow the format where one column labeled ‘INDEX’, which gives the ‘<teff>,<metallicity>,<logg>’ for each atmosphere, and then one column labeled ‘FILENAME’, which gives the path to the file containing that atmosphere.

• There is some flexibility as to how the atmosphere model files are organized. In BTSettle_2015_rebin, you’ll see that each file is simply stored in the same directory as the catalog.fits file, with one model per file. In phoenix_v16_rebin, the files are separated into sub-directory by metallicity, and then there is one file for each teff and then multiple columns within that file for different logg. It doesn’t matter what you choose, as long as it is reflected in the ‘INDEX’ column of catalog.fits.

• For the atmospheres, use units of angstroms for the wavelength and “FLAM” for flux ([erg/s/cm^2/A]; see pysynphot docs)

More detailed documentation on this is coming soon. In the meantime, let us know on the Github issue tracker if you’d like to implement a new atmospheric model grid.