ExoJAX

Version 1.6 (History)

Note: Paper II will be under peer review. We plan to release version 2.0 at the time of acceptance of the paper II.

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.