HEASoft and XSPEC are now available as conda packages. See details ....
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grad: accretion disk, Schwarzschild black hole
General Relativistic Accretion Disk model around a Schwarzschild black hole. Inner radius is fixed to be 3 Schwarzschild radii, thus the energy conversion efficiency is 0.057. See Hanawa (1989) and Ebisawa, Mitsuda & Hanawa (1991). Several bugs were found in the old GRAD model which was included in xspec 11.0.1ae and before. Due to these bugs, it turned out that the mass obtained by fitting the old GRAD model to the observation was 1.4 times over-estimated. These bugs were fixed, and a new parameter (par6) was added to make the distinction between the old and new codes clear.
| par1 | distance (kpc) |
| par2 | disk inclination angle (deg; 0 for face-on) |
| par3 | mass of the central object (solar units) |
| par4 | mass accretion rate  gm/s |
| par5 | spectral hardening factor, T /T . Should be
greater than 1.0, and considered to be 1.5–1.9 for accretion disks
around a stellar-mass black hole. See, e.g., Shimura and
Takahara (1995, ApJ, 445, 780) |
| par6 | A flag to switch on/off the relativistic effects (never allowed to be free). If positive, relativistic calculation; if negative or zero, Newtonian calculation (the inner radius is still fixed at 3 Schwarzschild radii, and the efficiency is 1/12). |
| norm | Should be fixed to 1. |
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