- 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 M0)
- 5. Mdot (kerrbb’s mass accretion rate in units of 1018 g/s)
- 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 0.01and 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 compiled following standard procedure for xspec (i.e., via “initpackage packname xkerrbb.dat /path/to/files/”), and then loaded into an xspec run in the same way (e.g., “lmod packname /path/to/files/”). 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.
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] M0, 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.