LogEmission¶

class sherpa.astro.optical.LogEmission(name='logemission')[source]¶

Bases: sherpa.models.model.ArithmeticModel

Gaussian function for modeling emission (log of fwhm).

It is for use when the independent axis is in Angstroms.

fwhm¶: The full-width half-maximum of the model in km/s.

pos¶: The center of the gaussian, in Angstroms.

flux¶: The normalisation of the gaussian.

skew¶: The skew of the gaussian.

limit¶: This is a hidden parameter and is unused by the model.

Notes

The functional form of the model for points is:

f(x) = fmax * (x / pos)^arg                    if x <= pos

       fmax * (x / pos)^(-alpha)               otherwise

arg = log(2) / log(1 + 0.5 * fwhm / c)

arg1 = log(2) / log(1 + 0.5 * skew * fwhm / c)

alpha = arg                                    if skew == 1

      = arg1                                   otherwise

fmax = (arg - 1) * flux / (2 * pos)            if skew == 1

     = (arg - 1) * flux / (pos * (1 + (arg - 1) / (arg1 - 1)))

                                               otherwise

c = 2.9979e5

and for integrated data sets the low-edge of the grid is used.

Attributes Summary

`thawedparhardmaxes`
`thawedparhardmins`
`thawedparmaxes`
`thawedparmins`
`thawedpars`

Methods Summary

`apply`(outer, \otherargs, \\*otherkwargs)
`calc`(p, x[, xhi])
`get_center`()
`guess`(dep, \args, \\*kwargs)	Set an initial guess for the parameter values.
`reset`()
`set_center`(\args, \\*kwargs)
`startup`()
`teardown`()

Attributes Documentation

thawedparhardmaxes¶

thawedparhardmins¶

thawedparmaxes¶

thawedparmins¶

thawedpars¶

Methods Documentation

apply(outer, *otherargs, **otherkwargs)¶

calc(p, x, xhi=None, **kwargs)[source]¶

get_center()¶

guess(dep, *args, **kwargs)¶

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.

reset()¶

set_center(*args, **kwargs)¶

startup()¶

teardown()¶