Last modified: December 2023

AHELP for CIAO 4.16 Sherpa


Context: models


The XSPEC compth model: Paolo Coppi's hybrid (thermal/non-thermal) hot plasma emission models.



The xscompth model is an additive model component.


The model is described at [1] .

Deprecated in Sherpa 4.10.0

The abhe parameter has been renamed ab_met to match the XSPEC definition. The name abhe can still be used to access the parameter, but this name will be removed in a future release.


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

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

   Param        Type          Value          Min          Max      Units
   -----        ----          -----          ---          ---      -----
   mdl.theta    thawed            1        1e-06        1e+06        keV
   mdl.showbb   frozen            1            0        10000           
   mdl.kT_bb    frozen          200            1       400000         eV
   mdl.RefOn    frozen           -1           -2            2           
   mdl.tau_p    frozen          0.1       0.0001           10           
   mdl.radius   frozen        1e+07       100000        1e+16         cm
   mdl.g_min    frozen          1.3          1.2         1000           
   mdl.g_max    frozen         1000            5        10000           
   mdl.G_inj    frozen            2            0            5           
   mdl.pairinj  frozen            0            0            1           
   mdl.cosIncl  frozen          0.5         0.05         0.95           
   mdl.Refl     frozen            1            0            2           
   mdl.Fe_abund frozen            1          0.1           10           
   mdl.Ab_met   frozen            1          0.1           10           
   mdl.T_disk   frozen        1e+06        10000        1e+06          K
   mdl.xi       thawed            0            0         5000           
   mdl.Beta     frozen          -10          -10           10           
   mdl.Rin      frozen           10        6.001        10000          M
   mdl.Rout     frozen         1000            0        1e+06          M
   mdl.redshift frozen            0            0            4           
   mdl.norm     thawed            1            0        1e+24           


The attributes for this object are:

Attribute Definition
kT_bb The temperature of the blackbody if greater than 0. When less than zero then the absolute value is used as the T_max parameter of the xsdispkpn model. The units are in eV.
tau_p The Thomson scattering depth.
radius The size of the scattering region in cm.
g_min The minimum Lorentz factor of the pairs.
g_max The maximum Lorentz factor of the pairs.
G_inj If less than zero then the non-thermal spectrum is assumed mono-energetic at g_max, otherwise a power law is used from g_min to g_max.
pairinj If zero then accelerated particles are electrons from thermal pool. If one then accelerated particles are electrons and positrons.
cosIncl The cosine of the inclination angle of the reflecting material to the line of sight.
Refl The fraction of the scattering region's emission intercepted by reflecting material.
Fe_abund The iron abundance with respect to solar.
Ab_met The abundance of the other metals with respect to solar.
T_disk The temperature of the reflecting disk, in K.
xi The ionization parameter of the reflector.
Beta The power-law index with radius of disk reflection emissivity.
Rin The inner radius of the reflecting material, in units of GM/c^2.
Rout The outer radius of the reflecting material, in units of GM/c^2.
redshift The redshift of the source.
norm The normalization of the model: see [1] for more details.


The precision of the numerical integration can be changed by using the set_xsxset function to set the value of the EQPAIR_PRECISION keyword, which defines the fractional precision. The default is 0.01 (1%).


XSPEC version

CIAO 4.16 comes with support for version 12.13.1e 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

xseqpair, xseqtherm