Pyrat Bay: Python Radiative Transfer in a Bayesian framework

A Forward-modeling and retrieval code to model exoplanet atmospheres and spectra.

Install as:

pip install pyratbay

or:

conda install -c conda-forge pyratbay

Docs at:

https://pyratbay.readthedocs.io/en/latest/

Cite as (ADS):

For the base code:

@ARTICLE{CubillosBlecic2021mnrasPyratBay,
       author = {{Cubillos}, Patricio E. and {Blecic}, Jasmina},
        title = "{The PYRAT BAY framework for exoplanet atmospheric modelling: a population study of Hubble/WFC3 transmission spectra}",
      journal = {\mnras},
     keywords = {radiative transfer, methods: statistical, planets and satellites: atmosphere, Astrophysics - Earth and Planetary Astrophysics, Astrophysics - Instrumentation and Methods for Astrophysics},
         year = 2021,
        month = aug,
       volume = {505},
       number = {2},
        pages = {2675-2702},
          doi = {10.1093/mnras/stab1405},
archivePrefix = {arXiv},
       eprint = {2105.05598},
 primaryClass = {astro-ph.EP},
       adsurl = {https://ui.adsabs.harvard.edu/abs/2021MNRAS.505.2675C},
      adsnote = {Provided by the SAO/NASA Astrophysics Data System}
}

For Multinest retrievals, radiative-equilibrium, TLS, isotopic ratios, and/or direct-imaging spectra:

@ARTICLE{CubillosEtal2026mnrasPyratBay2,
       author = {{Cubillos}, Patricio E. and {Blecic}, Jasmina and {Shulyak}, Denis and {Fossati}, Luca},
        title = "{PYRAT BAY 2.0: an upgraded framework for exoplanet atmosphere modelling in the JWST era}",
      journal = {\mnras},
     keywords = {radiative transfer, techniques: spectroscopic, planets and satellites: atmospheres, Earth and Planetary Astrophysics, Instrumentation and Methods for Astrophysics},
         year = 2026,
        month = sep,
       volume = {551},
       number = {3},
          eid = {stag1526},
        pages = {stag1526},
          doi = {10.1093/mnras/stag1526},
archivePrefix = {arXiv},
       eprint = {2608.07128},
 primaryClass = {astro-ph.EP},
       adsurl = {https://ui.adsabs.harvard.edu/abs/2026MNRAS.551g1526C},
      adsnote = {Provided by the SAO/NASA Astrophysics Data System}
}