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Last modified: January 2016

AHELP for CIAO 4.9 Sherpa v1


Context: contrib


Return the model spectrum in the form required by ChaRT2


(xlo, xhi, 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 ChaRT2 (the Chandra Ray Tracer). The x values are the low and high edges 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 *


Name Default value Description
id None Which dataset to use: if None then the value returned by get_default_id() will be used.
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> (xlo, xhi, ,y) = get_chart_spectrum()

Get the model values for the default dataset using the units expected by ChaRT2.

Example 2

sherpa> (xlo, xhi, 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.

Changes in the scripts 4.8.2 (January 2016) release

The routine has been updated to work with version 2 of ChART, so that the return value now contains three values rather than two.


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

See Also

get_conf, get_covar, get_int_proj, get_int_unc, get_proj, get_reg_proj, get_reg_unc
plot_chart_spectrum, save_chart_spectrum, sherpa_chart
get_areascal, get_arf, get_arf_plot, get_axes, get_backscal, get_bkg, get_bkg_plot, get_bkg_scale, get_coord, get_counts, get_data, get_data_plot, get_dep, get_dims, get_error, get_exposure, get_grouping, get_indep, get_quality, get_rmf, get_specresp, get_staterror, get_syserror
calc_stat_info, get_fit, get_stat_info
get_default_id, list_stats
get_draws, get_iter_method_name, get_iter_method_opt, get_method
get_model, get_model_component, get_model_component_image, get_model_component_plot, get_model_plot, get_num_par, get_order_plot, get_par, get_pileup_model, get_response, get_source, get_source_component_image, get_source_component_plot, image_source
get_kernel, get_psf
get_chisqr_plot, get_delchi_plot, get_prior, get_sampler, get_stat
get_analysis, get_rate
get_ratio, get_resid, image_getregion

Last modified: January 2016
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