James F. (“Jack”) Steiner

Astronomer at Large

Code — XSPEC Models

simplcut

simplcut is an extension of the simpl scattering kernel.

Important note! For either simpl or simplcut, you should use the energies command to define a broad energy grid over which the photons are redistributed. This should sufficiently cover both the seed distribution and ideally extend above a high-energy cutoff. E.g., energies 0.01 1000. 1000 log gives ~1% energy resolution in the grid from 10 eV to 1 MeV.

The model parameters are given below:

  1. Gamma — spectral index
  2. fsc — scattered fraction
  3. ReflFrac — reflection fraction. Negative values omit the transmitted component and return just the scattered spectrum.
  4. Energy Turnover — exponential cutoff Ecut when negative; kTe when positive, using nthcomp as an engine.

simplcut can be compiled using xspec – go from the command line in the installation directory. A tarball of the package is provided below.

Update (June 2026): a patched version of the package now works with ISIS as well as XSPEC (thanks to Cal Miller). There is no change for XSPEC users.

Model files:

kerrbb2

kerrbb2 is a modified version of Li-Xin Li’s code kerrbb, which combines the relativistic accretion disk models kerrbb and bhspec. It works using a table of spectral hardening values which have been computed by fitting bhspec-generated spectra with kerrbb at fixed sets of input values. The code needs to be compiled manually. An important restriction is that this release of kerrbb2 has been designed to operate over a luminosity range from 3% to 30% of the Eddington limit.

The model parameters are described below, where parameters 1–8 and 13 are the same as those in kerrbb:

  1. eta — kerrbb’s torque parameter, 0 by default
  2. a* — the spin
  3. i — inclination in degrees
  4. M — BH mass in M⊙
  5. Mdot — kerrbb’s mass accretion rate in units of 1018 g s−1
  6. D — the source distance in kpc
  7. rflag — returning-radiation flag (0/1)
  8. lflag — limb-darkening flag (0/1)
  9. fval — spectral hardening; values > 0 are taken as input, values < 0 (the default) interpolate over the table
  10. alpha — the viscosity term from bhspec; must be between 0.01 and 0.1
  11. NH — should be linked to the tbabs absorbing column in the fit
  12. idnum — the file index: the star in xftab*.dat; if 0 then taken as blank; if < 0, then xftab*.out is made with f and luminosity for eta = 0
  13. normalization — fix this to 1 for a given M, i, D

The kerrbb2 package can be compiled via xspec – go from the directory of the unpacked tarfile. When performing the data analysis, one should be sure to include the appropriate xftab*.dat file in the working directory. A tarball of the package is provided below.

Model files:

Spectral hardening tables (one per instrument; the number is the idnum parameter — put the file in your working directory):

Notes: NH is used not because kerrbb2 computes photoelectric absorption, but because NH affects the sensitivity range and weighting over the channels of a given instrument, and therefore it can moderately affect the spectral hardening.

Ranges over which the table has been computed: M = [3, 25] M⊙, i = [0, 85] degrees, a* = [−1, 0.99], L = [0.03, 0.3] LEdd, alpha = [0.01, 0.1], NH = [0, 20] × 1022 cm−2.