ExoJAX

Version 1.6 (History)

Notice

Paper II will be under peer review. We plan to release version 2.0 at the time of acceptance of the paper II. The documentation is currently undergoing a major revision. The revised documentation (develop branch version) might still provide clearer guidance, even for the current release version, while some features included may not yet be available in the release version. Jan 26th. (2025)

Warning

Recently, logging into HITRAN has become mandatory to access HITEMP files, causing issues with automated HITEMP file retrieval by RADIS. For more details, please refer to this resource. Feb 3rd. (2025)

ExoJAX provides an auto-differentiable high-resolution spectrum model for exoplanets/brown dwarfs using JAX. ExoJAX enables a fully Bayesian inference of the high-dispersion data to fit the line-by-line spectral computation to the observed spectrum, from end-to-end (i.e. from molecular/atomic databases to real spectra), by combining it with the Hamiltonian Monte Carlo in recent probabilistic programming languages such as NumPyro. So, the notable features of ExoJAX are summarized as

• HMC-NUTS, gradient-based optimizer available

• Easy to use the latest molecular/atomic data in ExoMol, HITEMP, HITRAN, and VALD3

• A transparent open-source project; anyone who wants to participate can join the development!

For a more geek-oriented explanation

ExoJAX is a spectral model based on the Differentiable Programming (DP) paradigm! ExoJAX aims to provide building blocks for retrieval code, much like Minecraft 🧱.

🟢 If you have an error and/or want to know the up-to-date info, visit ExoJAX wiki. Or use the discussions form on github or directly raise issues.

Contents

• Installation and References

Tutorials:

• Basics
  • Get Started
  • HMC-NUTS Retrieval of a Methane High-Resolution Emission Spectrum
• Applications
  • Tips for Real Analysis
  • Transmission Spectra
  • Reflection Spectrum
  • Molecular/Atomic/Continuum Databases
• Multi Molecule/Segments Mdb and Opa Handler
  • Multi Molecule Handler
• Manual Settings of Opacity (not using opa)
  • Cross Section using Various Opacity Calculators
• Others
  • Scattering
  • Micro Chemical/Physical Processes
  • Macro Physical Processes
  • Others

User Guide:

• Molecular Database
  • Molecular and Atomic Databases (mdb / adb)
  • ExoMol, HITEMP, HITRAN
  • Non-air broadening
  • VALD3
• Opacity Calculation
  • Opacity Calculator Classes (opa)
  • Voigt-Hjerting Function and Voigt Profile
  • MODIT
  • PreMODIT
  • Benchmark
  • 32 and 64 bit in ExoJAX
• Scattering and Clouds
  • Rayleigh scattering
  • Particulates Database (pdb)
  • Mie Scattering
  • Atmospheric Microphysics (amp)
  • Terminal Velocity of Cloud Particles
  • Comparison the AM geometric opacity with PieMieScatt
  • Comparison of the ExoJAX AM cloud model with VIRGA
• Radiative Transfer
  • Radiative Transfer
  • Flux-based Emission with pure absorption
  • Intensity-based Emission with pure absorption
  • Flux-based Emission with Scattering
  • Flux-based Reflection Spectrum
  • Transmission Spectroscopy
• Spectral Operators
  • Spectral Operators (sop)
• Others
  • Compatibility to External Packages
• For Developers
  • Test codes for developers
  • Generates documents
• History
  • History

API:

• exojax package

ExoJAX example (exojaxample)

• 🪐 exojaxample_WASP39b : An example of HMC-NUTS for actual hot Saturn (JWST/ERS, NIRSPEC/G395H)

• 🪐 exojaxample_jupiter : An example of HMC-NUTS for actual Jupiter reflection spectrum

References

• Kawahara, Kawashima, Masuda, Crossfield, Pannier, van den Bekerom, ApJS 258, 31 (2022) (Paper I)

• Kawahara et al., 2024, in prep. (Paper II)

License & Attribution

Copyright 2021-2024, Contributors

• Hajime Kawahara (@HajimeKawahara, maintainer)

• Yui Kawashima (@ykawashima, co-maintainer)

• Kento Masuda (@kemasuda)

• Ian Crossfield

• Dirk van den Bekerom (@dcmvdbekerom)

• Daniel Kitzmann (@daniel-kitzmann)

• Brett Morris (@bmorris3)

• Erwan Pannier (@erwanp) and Nicolas Minesi (@minouHub) from RADIS community

• Stevanus Nugroho (@astrostevanus)

• Tako Ishikawa (@chonma0ctopus)

• Yui Kasagi (@YuiKasagi)

• Shotaro Tada (@sh-tada)

• Ko Hosokawa (@KoHosokawa)

• Hibiki Yama

ExoJAX is free software made available under the MIT License. See the LICENSE.