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For on-line information type: cl> help using_spectral
The models provided are:
parameter 1 = | logarithmic value of Galactic NH in units of cm-2 |
parameter 2 = |
logarithmic value of Intrinsic NH in units of cm-2 |
parameter 3 = |
redshift of source |
If only one parameter is given, it is assumed to be the Galactic NH.
If only two parameters are given, they are assumed to be the Intrinsic NH and the redshift.
parameter 1 = | normalization - logarithmic value of the flux density at 1 keV in units of keV cm-2 s-1 keV-1 |
parameter 2 = |
energy index defined as
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parameter 1 = | normalization - logarithmic value of the flux density at 1 keV in units of keV cm-2 s-1 keV-1 |
parameter 2 = |
temperature in the source frame in KeV |
parameter 1 = | normalization - logarithmic value of the flux density at 1 keV in units of keV cm-2 s-1 keV-1 |
parameter 2 = | temperature in the source frame in KeV |
parameter 1 = | normalization - logarithmic value of the flux density at 1 keV in units of keV cm-2 s-1 keV-1 |
parameter 2 = | temperature in the source frame in keV |
parameter 1 = | normalization - logarithmic value of the ratio of
the volume emission
measure to
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parameter 2 = |
temperature in the source frame in keV |
parameter 3 = |
abundance table |
c - cosmic | |
m - Meyer | |
parameter 4 = |
percentage of heavy elements (100 is the solar value) |
parameter 1 = | normalization - logarithmic value of the normalization of the gaussian in units of keV cm-2 s-1. |
parameter 2 = | line centroid in keV |
parameter 3 = |
FWHM of the line in keV |
For detailed information on model parameters, please refer to the
science specifications in xspectraldoc$spectral.(tex,dvi).
The spectral model and its parameters are passed to the fitting tasks as:
More than one absorption and more than one spectral model can be
combined in the following ways:
absorption1(params)*model1(params)+absorption2(params)*model2(params)...
or
absorption(params)*(model1(params)+model2(params)...+modelN(params))
Some basic rules for writing a model description:
abs(18:20) * ( power(0:2) + brems ( log(0.5), 0:20) )
NOTE: When different spectral models with different units for the normalization are combined, the relative normalization of the second model can be quite large.
For example: ray(1:2,c,100)+pow(11:13,1:2)
specifies a power-law model with a flux of approximately 1% of the flux in the Raymond model.
See cl> help models_spectral for more information on syntax.
Examples:
to describe a power law model spectrum, with energy index varying between 1 and 2, and a galactic absorption varying between 1020 and 1021 cm-2.
for two power law models, and one absorption applied to both of them. The galactic absorption can vary between 1020 and 1021 cm-2, the intrinsic absorption is fixed at 1023, for an object at z=1. The energy index of the first power law model can vary between 1 and 2, with the best fit normalization calculated by the program. The second power law has a fixed index of 1.5, and its normalization is allowed to vary between 50 and 60 % of the first one.
to describe two power law models, each with galactic absorption in two different ranges.