POSEIDON’s documentation

POSEIDON is a Python package designed to rapidly retrieve atmospheric properties from exoplanet spectra. POSEIDON has two main components: (1) a ‘forward’ model, TRIDENT, that generates 1D, 2D, or 3D transmission spectra; and (2) a nested sampling retrieval framework that uses the sampling algorithm PyMultiNest, wrapped around TRIDENT, to explore the range of atmospheric properties consistent with an observed exoplanet transmission spectrum.

POSEIDON’s official features currently include:

• Transmission spectra modelling for 1D, 2D, and 3D exoplanet atmospheres.

• Rapid atmospheric retrievals that can run on your laptop.

• Model support for planets ranging from ultra-hot Jupiters to temperate terrestrials.

• Parametric prescriptions for stellar contamination, multidimensional clouds, and more.

• High-resolution line-by-line models (\(R \sim 10^6\)) for cross correlation analyses.

Beta features:

• Chemical equilibrium retrievals.

• Emission spectra modelling and retrievals for 1D, cloud-free atmospheres without scattering.

The initial public release of POSEIDON contains a range of tutorials on generating forward models and a tutorial on running atmospheric retrievals. Tutorials on multidimensional retrievals will be added soon.

New in POSEIDON v1.1:

To use these new features, you will need to re-download the POSEIDON input data. See the installation instructions.

• Chemical equilibrium models and retrievals, demonstrated in two new tutorials.

• JWST proposal tutorial (PandExo + retrieving simulated JWST data).

• Bayesian model comparison demonstration in first retrieval tutorial.

• Improved stellar contamination retrieval capabilities (e.g. spots + faculae).

See the POSEIDON Release Notes on GitHub for more details.

License:

POSEIDON is available under the BSD 3-Clause License. If you use POSEIDON, please cite MacDonald & Madhusudhan (2017) and MacDonald (2023). Additionally, if you make use of the multidimensional transmission spectra modelling capabilities, we would appreciate a citation for the TRIDENT methods paper: MacDonald & Lewis (2022).

Contributor Hall of Fame:

Ryan MacDonald, Ruizhe Wang, Elijah Mullens

Guide:

• Forward Model Tutorials
  • Generating Transmission Spectra
  • Multidimensional Transmission Spectra with TRIDENT
  • Chemical Equilibrium Transmission Spectra
  • High-Resolution Spectroscopy
  • Transmission Spectra for Terrestrial Planets
  • Generating Secondary Eclipse Emission Spectra
• Retrieval Tutorials
  • Atmospheric Retrievals with POSEIDON
  • Chemical Equilibrium Retrievals
  • Supporting a JWST Proposal with POSEIDON
• Opacity Database

Code Documentation:

• Contributing to POSEIDON
• API Reference
  • POSEIDON