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ExoJAX

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, HITRAN/HITEMP and VALD3

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

🟢 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
• Quick Look for Observers
• Databases

Tutorials:

• Basics
  • Simple Usage
  • Cross Section using Various Opacity Calculators
  • Forward Modeling
  • Reverse Modeling (a.k.a Retrieval) using Various Opacity Calculators
  • Gradient-based Optimization of Spectra
  • Micro Chemical/Physical Processes
  • Macro Physical Processes
  • Others

User Guide:

• User Guide
  • Voigt-Hjerting Function and Voigt Profile
  • ExoMol, HITEMP, HITRAN common API
  • Loading HITEMP for Each Isotope
  • Parition Function (Ratio) for Each Isotope
  • Molecular Database and Conversion
  • ExoMol
  • HITRAN/HITEMP
  • VALD3
  • Radiative Transfer
  • Modified Discrete Integral Transform (MODIT)
  • Benchmark: LPF vs MODIT
  • F32 and F64
  • Terminal Velocity of Cloud Particles
  • Compatibility to External Packages
• For Developers
  • Test codes for developers
  • Generating Documents
  • Experimental module

API:

• exojax package

References

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

License & Attribution

Copyright 2021-2022, Contributors

• Hajime Kawahara (@HajimeKawahara, maintainer)

• Yui Kawashima (@ykawashima)

• Kento Masuda (@kemasuda)

• Ian Crossfield

• Dirk van den Bekerom (@dcmvdbekerom)

• Daniel Kitzmann (@daniel-kitzmann)

• Brett Morris (@bmorris3)

• Erwan Pannier (@erwanp) and RADIS community

• Stevanus Nugroho (@astrostevanus)

• Tako Ishikawa (@chonma0ctopus)

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