Last modified: December 2020

AHELP for CIAO 4.13 Sherpa v1


Context: models


The XSPEC jet model: Leptonic relativistic jet model.



The xsjet model is an additive model component.


The model is described at [1] .


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

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

   Param        Type          Value          Min          Max      Units
   -----        ----          -----          ---          ---      -----
   mdl.mass     frozen        1e+09            1        1e+10      solar
   mdl.Dco      frozen       3350.6            1        1e+08        Mpc
   mdl.log_mdot thawed           -1           -5            2  logL/lEdd
   mdl.thetaobs frozen            3            0           90        deg
   mdl.BulkG    frozen           13            1          100           
   mdl.phi      frozen          0.1         0.01          100        rad
   mdl.zdiss    frozen         1275           10        10000         Rg
   mdl.B        frozen          2.6         0.01           15        Gau
   mdl.logPrel  frozen         43.3           40           48           
   mdl.gmin_inj frozen            1            1         1000           
   mdl.gbreak   frozen          300           10        10000           
   mdl.gmax     frozen         3000         1000        1e+06           
   mdl.s1       frozen            1           -1            1           
   mdl.s2       frozen          2.7            1            5           
   mdl.z        frozen            0            0           10           
   mdl.norm     frozen            1            0        1e+24           


The attributes for this object are:

Attribute Definition
mass Black hole mass, in solar masses.
Dco Comoving distance, as in XSoptxagnf.
log_mdot log (accretion power / Eddington luminosity), in units of log L / logLEdd. See [1] for a full discussion of this parameter.
thetaobs The inclination angle (deg) between the jet axis and line of sight.
BulkG Bulk lorentz factor of the jet.
phi The angular size scale - in radians - of the jet acceleration region as seen from the black hole. See [1] for more details.
zdiss The vertical distance from the black hole of the jet dissipation region, in units of Rg=GM/c^2. See [1] for more details.
B The magnetic field (in Gauss) in the jet.
logPrel The log of the power injected in relativisitic particles, which is measured in ergs/s.
gmin_inj The minimum lorentz factor of the injected electrons.
gbreak The lorentz factor of the break in injected electron distribution.
gmax The maximum lorentz factor.
s1 The injected index of the electron distribution below the break.
s2 The injected index of the electron distribution above the break.
z The cosmological redshift corresponding to the Dco parameter.
norm MUST BE FIXED AT UNITY as the jet spectrum normalisation is set by the relativisitic particle power.


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.