Pyrat Bay

Python Radiative Transfer in a Bayesian framework

Build Status Documentation Status Latest Version conda License

Author:

Patricio Cubillos & Jasmina Blecic

Contact:

patricio.cubillos[at]oeaw.ac.at

Organizations:

Space Research Institute (IWF)

Web site:

https://github.com/pcubillos/pyratbay

Date:

Aug 10, 2026

Features

Pyrat Bay is an efficient, user-friendly Python tool to compute radiative-transfer spectra, and fit exoplanet atmospheric properties. This package offers:

  • Transmission, eclipse, or emission spectral synthesis of exoplanet atmospheres.

  • Forward-model or (multinest) retrieval calculations.

Radiative-transfer calculations include opacity sources from:

  • Line-by-line molecular absorption

  • Collision-induced absorption

  • Rayleigh scattering absorption

  • Na and K alkali resonant lines

  • Gray and Mie (soon) aerosol opacities

Bayesian (Nested sampling) posterior sampling of atmospheric parameters:

  • Molecular abundances (free-, equilibrium-, or hybrid chemistry)

  • Temperature profiles

  • Pressure-radius

  • Rayleigh and cloud properties

  • Transit light source effect (TLS)

  • Offsets between observing instruments

  • Error scaling for observations

  • Isotopic-ratio fitting

Contributors

Be Kind

If you found Pyrat Bay useful for your research, please cite this article:

Cubillos & Blecic (2021): The Pyrat Bay Framework for Exoplanet Atmospheric Modeling: A Population Study of Hubble/WFC3 Transmission Spectra, MNRAS, 505, 2675.

Please prefer to channel your feedback or inquiries through the Github issue tracker: https://github.com/pcubillos/pyratbay, or alternatively through this email: patricio.cubillos[at]oeaw.ac.at.

Pyrat Bay is open-source software under the GNU GPL v2 license (see License) and is compatible with Python>=3.10.

Documentation