Last modified: December 2023

AHELP for CIAO 4.16 Sherpa


Context: models


The XSPEC compmag model: Thermal and bulk Comptonization for cylindrical accretion onto the polar cap of a magnetized neutron star.



The xscompmag model is an additive model component.


The model is described at [1] .


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

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

   Param        Type          Value          Min          Max      Units
   -----        ----          -----          ---          ---      -----
   mdl.kTbb     thawed            1          0.2           10        keV
   mdl.kTe      thawed            5          0.2         2000        keV
   mdl.tau      thawed          0.5            0           10           
   mdl.eta      thawed          0.5         0.01            1           
   mdl.beta0    thawed         0.57       0.0001            1           
   mdl.r0       thawed         0.25       0.0001          100           
   mdl.A        frozen        0.001            0            1           
   mdl.betaflag frozen            1            0            2           
   mdl.norm     thawed            1            0        1e+24           


The attributes for this object are:

Attribute Definition
kTbb The seed blackbody temperature, in keV.
kTe The electron temperature of the accretion column, in keV.
tau The vertical optical depth of the accretion column, with electron cross-section equal to 10^-3 of the Thomson cross-section.
eta The index of the velocity profile when the accretion velocity increases towards the neutron star (valid when betaflag is 1).
beta0 The terminal velocity of the accreting matter at the neutron star surface (valid when betaflag is 1).
r0 The radius of the accretion column in units of the neutron star Schwarzschild radius.
A The albedo at the surface of the neutron star.
betaflag A flag for setting the velocity profile of the accretion column, described at [1] . It has values of 1 or 2 and can not be thawed.
norm The normalization of the model: see [1] for an explanation of the units.


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.