Last modified: December 2020

AHELP for CIAO 4.13 Sherpa v1


Context: models


The XSPEC kerrbb model: multi-temperature blackbody model for thin accretion disk around a Kerr black hole.



The xskerrbb model is an additive model component.


The model is described at [1] .


>>> create_model_component("xskerrbb", "mdl")
>>> print(mdl)

Create a component of the xskerrbb model and display its default parameters. The output is:

   Param        Type          Value          Min          Max      Units
   -----        ----          -----          ---          ---      -----
   mdl.eta      frozen            0            0            1           
   mdl.a        thawed            0           -1       0.9999           
   mdl.i        frozen           30            0           85        deg
   mdl.Mbh      thawed            1            0          100       Msun
   mdl.Mdd      thawed            1            0         1000       Mdd0
   mdl.Dbh      frozen           10            0        10000        kpc
   mdl.hd       frozen          1.7            1           10           
   mdl.rflag    frozen            1         -100          100           
   mdl.lflag    frozen            0         -100          100           
   mdl.norm     thawed            1            0        1e+24           


The attributes for this object are:

Attribute Definition
eta The ratio of the disk power produced by a torque at the disk inner boundary to the disk power arising from accretion. See [1] for more details.
a The specific angular momentum of the black hole in units of the black hole mass M (when G=c=1). It should be in the range [-1, 1).
i The disk inclination angle, in degrees. A face-on disk has i=0. It must be less than or equal to 85 degrees.
Mbh The mass of the black hole, in solar masses.
Mdd The "effective" mass accretion rate in units of 10^18 g/s. See [1] for more details.
Dbh The distance from the observer to the black hole, in units of kpc.
hd The spectral hardening factor, Tcol/Teff. See [1] for more details.
rflag A flag to switch on or off the effect of self irradiation: when greater than zero the self irradition is included, otherwise it is not. This parameter can not be thawed.
lflag A flag to switch on or off the effect of limb darkening: when greater than zero the disk emission is assumed to be limb darkened, otherwise it is isotropic. This parameter can not be thawed.
norm The normalization of the model. It should be fixed to 1 if the inclination, mass, and distance are frozen.


XSPEC version

CIAO 4.13 comes with support for version 12.10.1s of the XSPEC models. This can be checked with the following:

% python -c 'from sherpa.astro import xspec;


See the bugs pages on the Sherpa website for an up-to-date listing of known bugs.

See Also