Radix.jl

A spectral simulator for photo-ionized plasmas at X-ray frequencies.

Radix is based on Tim Kallman's XSTAR program, which is written in Fortran. A Julia version is more modular, extendable and performant: the rates of the atomic processes, the level balance, the thermal equilibrium, the transfer of the radiation through a slab and the emitted spectrum are separate functions that return arrays, and the results can be used as a model of a spectral fit or written to one FITS file. Each step has been validated against XSTAR 2.59j.

Quick start

using Radix
model = Model("atdb.fits", "coheat.dat")        # the atomic data and the Compton table of an XSTAR installation
run = slab(model; density=1e4, column=1e21, logξ=1.0, luminosity=1e46, equilibrium=true, T=10.0, emult=1.0, steps=3, vturb=0.0)
[(z.T, z.xee, z.Δr) for z in run.zones]         # the zones: temperature (10⁴ K), electron fraction and thickness (cm)

Start Julia with several threads (julia -t auto): the elements of the gas are solved in parallel.

Contents

• Using Radix
• • A slab
  • What comes back
  • Results as arrays, and one file
  • Agreement with XSTAR
  • Speed
  • Running the tests
• Reference
• • Models and results
  • Sources
  • Atomic data
  • Constants
  • Internals
• Field names for Radix rate types
• • Rules
  • Shared vocabulary
  • Transition and Parent
  • Verified against the Fortran and the data
  • Bugs found and fixed
  • Radiation and Opacity
  • Level data in the coefficients
  • Physical constants
  • Heating, cooling and thermal equilibrium
  • Transfer: escape probabilities and optical depths
  • Reference tests
  • Automatic differentiation
  • Open items
  • Fields of every type