Line profiles from a Keplerian disk around a black hole

This model calculates the line profile from a Keplerian Accretion disk around both Schwarzschild & Kerr (arbitrary spin) black holes. For bug reports, feature requests, etc. please contact It requires the use of an extensive set of transfer functions, which must be downloaded (see below). Each of the files contain a transfer function for a given black hole spin. All of the zip files MUST be unzipped in within the directory $LHEASOFT/../spectral/xspec/manager/XSKDLINE/ for v11 or $HEADAS/../spectral/modelIonData/ for v12. The model can be used in two distinct forms within XSPEC:

  • As an additive model, called using one of
    • XSPEC>mo kdline0
    • XSPEC>mo kdline1
  • As a convolution model, called using one of (e.g.)
    • XSPEC>mo kdconv0*compps
    • XSPEC>mo kdconv1*compps
Each of these forms can be run in two distinct modes (denoted by kdlineN,kdconvN; where N is either 0 or 1):

Mode 0 (kdline0,kdconv0)

The accretion disk is assumed to extend down to the marginally stable orbit for a particular black hole spin. The value of the spin parameter is determined by inversion of Rms(a) (see e.g. Bardeen, Press & Teulkolsky, 1974). The model can be used to fit to the value of Rms & hence determine a, which is displayed by setting:
XSPEC>chatter 12

Mode 1 (kdline1,kdconv1)

The model does not assume that the disk extends down to the innermost stable orbit. Instead, the line profile is calculated by specifying the black hole spin, a; the inner (Rmin) & outer (Rmax) edges of the disk; along with inclination, etc. Due to the method used by XSPEC to perform spectral fitting, the radii are c set in units such that Rms(a) = 1, Rout = 100. Unless the user is certain of what they are doing, it is STRONGLY advised that the spectral fit is started using the default settings of the model. Upon the completion of a fitting procedure, the user can determine the values of the radii in units of GMc^{-2} by setting:
XSPEC>chatter 12


If you use these models, please cite:


The source code files required are xskdc0.f, xskdc1.f, xskdconv.f, xskdl0.f, xskdl1.f, xskdline.f. The parameter information is in xskd_lmodel.dat and a more detailed description of the model in xskd_readme.txt. All these files are available in If you are running xspec versions prior to 11.3.2b then you need to edit xskdline.f and replace the instances of fgmodf with fgdatd.

The transfer function files are,,,,,,,,,,, Note that each of these files is approximately 200 Mbytes.

Keith Arnaud, Lab. for High Energy Astrophysics, NASA/Goddard Space Flight Center

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Last modified: Friday, 13-May-2005 10:57:08 EDT