Last modified: December 2023

AHELP for CIAO 4.16 Sherpa


Context: models


The XSPEC bwcycl model: Becker-Wolff self-consistent cyclotron line model.



The xsbwcycl model is an additive model component.


The model is described at [1] . Please review the restrictions on the model and parameter values at this reference before using the model.


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

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

   Param        Type          Value          Min          Max      Units
   -----        ----          -----          ---          ---      -----
   mdl.Radius   frozen           10            5           20         km
   mdl.Mass     frozen          1.4            1            3      Solar
   mdl.csi      thawed            3         0.01           20         thawed            1         0.01           20           
   mdl.B        thawed            4         0.01          100      1e12G
   mdl.Mdot     thawed            1        1e-06        1e+06    1e17g/s
   mdl.Te       thawed            5          1.3          100        keV
   mdl.r0       thawed           44           10         1000          m
   mdl.D        frozen            5            1           20        kpc
   mdl.BBnorm   frozen            0            0          100           
   mdl.CYCnorm  frozen            1           -1          100           
   mdl.FFnorm   frozen            1           -1          100           
   mdl.norm     frozen            1            0        1e+24           


The attributes for this object are:

Attribute Definition
Radius The radius of the Neutron star, in km. Keep frozen.
Mass The mass of the Neutron star, in solar units. Keep frozen.
csi Parameter linked to the photon escape time (order of some unities).
delta Ratio between bulk and thermal Comptonization importances.
B The magnetic field in units of 10^12 G.
Mdot The mass accretion rate, in 10^17 g/s.
Te The electron temperature in units of keV.
r0 The column radius in m.
D The source distance in kpc. Keep frozen.
BBnorm The normalization of the blackbody seed photon component (fix it to zero at first).
CYCnorm The normalization of the cyclotron emission seed photon component (fix it to one).
FFnorm The normalization of the Bremsstrahlung emission seed photon component (fix it to one).
norm The normalization of the model (fix it to one).


Changes in CIAO

Changed in CIAO 4.14

The D parameter now displays the correct units (kpc) rather than km.

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.