get_chart_spectrum

Context: contrib

Synopsis

Return the model spectrum in the form required by ChaRT

Syntax

(x,y) = get_chart_spectrum( [id=None, elow=None, ehigh=None,
ewidth=None, norm=None] )

The get_chart_spectrum() command turns the current model values into the form expected by ChaRT, the Chandra Ray Tracer. The x values are the mid-points of each bin, and are in keV; the y values are the model flux in units of photon/cm^2/s (they give the integrated flux for each bin, rather than the flux density as displayed by the plot_source command).

Please see the ChaRT preparation thread for further information on how to use this routine.

Loading the routine

The routine can be loaded into Sherpa by saying:

from sherpa_contrib.chart import *

Arguments

Name	Default value	Description
id	None (which means use the value of get_default_id)	Which dataset to use.
elow	None	The minimum energy at which to evaluate the model; this parameter controls the lower edge of the lowest-energy bin, and is in keV. A value of None means to use the lowest energy bin from the ARF grid. This value should not be smaller than 0.2 keV.
ehigh	None	The maximum energy at which to evaluate the model; this parameter controls the upper edge of the highest-energy bin, and is in keV. A value of None means to use the highest energy bin from the ARF grid. This valus should not be larger than 10 keV.
ewidth	None	The bin width to use, in keV. A value of None means to use the bin width from the ARF grid.
norm	None	A scaling factor to allow you to easily change the overall flux of the model. A value of None is equivalent to a factor of 1; a value of 10 would create a ChaRT spectral model ten times brighter than the input model.

Example 1

sherpa> (x,y) = get_chart_spectrum()

Get the model values for the default dataset using the units expected by ChART.

Example 2

sherpa> (x,y) = get_chart_spectrum(elow=1, ehigh=8)

In this example the returned values are restricted to the range 1 to 8 keV, using the default binning given by the ARF grid. Note that this energy range need not overlap the range used to fit the data (or even the energy ranges of the ARF and RMF files). It should however remain within the range 0.2 to 10 keV.

Bugs

See the bugs pages on the Sherpa website for an up-to-date listing of known bugs.