Seaton

class sherpa.astro.optical.Seaton(name='seaton')

Bases: sherpa.models.model.ArithmeticModel

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])
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)

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()