Seaton

class sherpa.astro.optical.Seaton(name='seaton')[source] [edit on github]

Bases: sherpa.models.model.RegriddableModel1D

Galactic extinction: the Seaton model from Synphot.

The interstellar extinction is calculated using the formula from [1] as implemented in STSCI’s Synphot program [2]. The supported wavelength range is 1000 to 10000 Angstroms, and the Notes section describes the changes from [1]. This model is intended to be used to modify another model (e.g. by multiplying the two together). It is for use when the independent axis is in Angstrom.

ebv

E(B-V)

See also

CCM, FM, LMC, SM, SMC, XGAL

Notes

The formulae are based on an adopted value of R=3.20.

For wavelengths above 3704 Angstrom, the function interpolates linearly in 1/lambda in table 3 [1]. For wavelengths below this, the formulae from table 2 [1] are used (see also [3], corrected to R=3.2). The formulae match at the endpoints of their respective intervals. There is a mismatch of 0.009 mag/ebmv at nu=2.7 (lambda=3704 Angstrom). Seaton’s tabulated value of 1.44 mag at 1/lambda = 1.1 may be in error; 1.64 seems more consistent with his other values.

For wavelengths below 1000 Angstrom, a constant value equal to the value at 1000 Angstrom is used. For wavelengths above 10000 Angstroms a linear extrapolation (in 1/lambda) is used.

When evaluated on a binned grid, the lower-edges of the bins are used for the calculation.

References

[1](1, 2, 3, 4) Seaton, M. J. 1979, MNRAS, 187, 73 http://adsabs.harvard.edu/abs/1979MNRAS.187P..73S
[2]http://www.stsci.edu/institute/software_hardware/stsdas/synphot
[3]Nandy et al., 1975, A&A, 44, 195-203. http://adsabs.harvard.edu/abs/1975A%26A….44..195N

Attributes Summary

thawedparhardmaxes
thawedparhardmins
thawedparmaxes
thawedparmins
thawedpars

Methods Summary

apply(outer, *otherargs, **otherkwargs)
calc(p, x[, xhi]) Evaluate the model on a grid.
get_center()
guess(dep, *args, **kwargs) Set an initial guess for the parameter values.
regrid(*arrays)
reset()
set_center(*args, **kwargs)
startup(cache) 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) [edit on github]
calc(p, x, xhi=None, **kwargs)[source] [edit on github]

Evaluate the model on a grid.

Parameters:
  • p (sequence of numbers) – The parameter values to use. The order matches the pars field.
  • *args – The model grid. The values can be scalar or arrays, and the number depends on the dimensionality of the model and whether it is being evaluated over an integrated grid or at a point (or points).
get_center() [edit on github]
guess(dep, *args, **kwargs) [edit on github]

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) [edit on github]
reset() [edit on github]
set_center(*args, **kwargs) [edit on github]
startup(cache) [edit on github]

Called before a model may be evaluated multiple times.

See also

teardown()

teardown() [edit on github]

Called after a model may be evaluated multiple times.

See also

setup()