Last modified: December 2018

URL: http://cxc.harvard.edu/sherpa/ahelp/bbody.html
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AHELP for CIAO 4.11 Sherpa v1

bbody

Context: models

Synopsis

A one-dimensional Blackbody model.

Syntax

bbody

Description

A model representing the ideal blackbody function. It can be used when the independent axis is in energy or wavelength space.


Example

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

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

mdl
   Param        Type          Value          Min          Max      Units
   -----        ----          -----          ---          ---      -----
   mdl.space    frozen            0            0            1 0 - energy | 1 - wave
   mdl.kT       thawed            1          0.1         1000        keV
   mdl.ampl     thawed            1        1e-20        1e+20           

ATTRIBUTES

The attributes for this object are:

space

Switch to select whether the independent axis is energy or wavelength. This parameter is not fit ( alwaysfrozen is set), and should be set to either 0, when the independent axis is energy with units of keV, or 1 when the axis is wavelength with units of Angstrom.

kT

The temperature if the blackbody, in keV.

ampl

The amplitude of the blackbody component.

Notes

The blackbody emission is calculated as a function of energy using the expression:

f(E) = ampl * E^2 / (exp(E / kT) - 1)

where E is the photon energy, and kT is the blackbody temperature (both in keV). The amplitude, ampl, is related to the ratio of source radius to distance by:

ampl = (2 * pi / (c^2 * h^3)) (R / d)^2
     = 9.884 x 10^31 (R / d)^2

with Planck's constant (h) specified in keV-s and the speed of light (c) specified in cm/s, and with R and d representing the radius of, and distance to, the source respectively.

There are two conditions when the above equation is not used:


Bugs

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

See Also

models
bbodyfreq