BBody

class sherpa.astro.models.BBody(name='bbody')[source]

Bases: sherpa.models.model.RegriddableModel1D

A one-dimensional Blackbody model.

This model can be used when the independent axis is in energy or wavelength space.

space

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.

See also

BBodyFreq

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:

  • if E/kt < 10^-4 then f(E) = ampl * E * kT
  • if E/kT > 60, f(E) = 0.

Attributes Summary

thawedparhardmaxes
thawedparhardmins
thawedparmaxes
thawedparmins
thawedpars

Methods Summary

apply(outer, *otherargs, **otherkwargs)
calc(pars, xlo, *args, **kwargs)
get_center()
guess(dep, *args, **kwargs) Set an initial guess for the parameter values.
regrid(*arrays)
reset()
set_center(*args, **kwargs)
startup() Called before a model may be evaluated multiple times.
teardown() Called after a model may be evaluated multiple times.

Attributes Documentation

thawedparhardmaxes
thawedparhardmins
thawedparmaxes
thawedparmins
thawedpars

Methods Documentation

apply(outer, *otherargs, **otherkwargs)
calc(pars, xlo, *args, **kwargs)
get_center()
guess(dep, *args, **kwargs)[source]

Set an initial guess for the parameter values.

Attempt to set the parameter values, and ranges, for the model to match the data values. This is intended as a rough guess, so it is expected that the model is only evaluated a small number of times, if at all.

regrid(*arrays)
reset()
set_center(*args, **kwargs)
startup()

Called before a model may be evaluated multiple times.

See also

teardown()

teardown()

Called after a model may be evaluated multiple times.

See also

setup()