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Last modified: December 2013

URL: http://cxc.harvard.edu/sherpa/ahelp/eqwidth.html
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AHELP for CIAO 4.9 Sherpa v1

eqwidth

Context: utilities

Synopsis

Calculate the equivalent width of an emission or absorption line.

Syntax

eqwidth(src, combo, [lo, hi], [id], [bkg_id])

Description

The eqwidth command calculates the equivalent width of an emission or absorption line in the source or background data. The equivalent width is reported in the units of the analysis, either energy or wavelength.

An integral over the entire energy or wavelength range of the dataset - or a specified interval - is performed to evaluate the continuum model (src) and the continuum-plus-line model (combo) at each point. The integrand is then (combo-src)/src.

  • src - model expression that describes the continuum
  • combo - model expression that describes the continuum plus the line
  • lo - low energy/wavelength limit; default=None
  • hi - high energy/wavelength limit; default=None
  • id - the id of the dataset to use; if not given, uses the default dataset id (id=1 by default, see "ahelp get_default_id")
  • bkg_id - the id of the background to use; default is the first background dataset

The src and combo model expression components must be established, e.g. with set_source or set_model(), before they can be used by eqwidth.

Example 1

sherpa> set_source(powlaw1d.cont + gauss1d.eline)
sherpa> eqwidth(cont, cont+eline)
0.535073

Define 1D gaussian and powerlaw models, then use them to find the equivalent width of the line.

Example 2

sherpa> set_bkg_source(2, const1d.c1+gauss1d.line)
sherpa> eqwidth(c1, c1+line, lo=2., hi=10., id=2, bkg_id=1)

Define 1D constant and powerlaw models for background data set 1 associated with source data set 2, then use them to find the equivalent width of the line between 2.0 and 10.0 keV.

Example 3

sherpa> set_source("src",
bbody.bb+powlaw1d.pl+gauss1d.line1+gauss1d.line2)
sherpa> eqwidth(bb+pl, bb+pl+line1, "src")
0.454946

Model components from the source model are used to calculate the equivalent width of a line in dataset "src".

Bugs

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

See Also

data
get_bkg_plot
info
list_model_ids, show_bkg_model, show_bkg_source
modeling
add_model, add_user_pars, clean, create_model_component, delete_bkg_model, delete_model, delete_model_component, get_model, get_model_autoassign_func, 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_source, get_source_component_image, get_source_component_plot, image_model, image_model_component, image_source, image_source_component, integrate, integrate1d, link, load_table_model, load_template_model, load_user_model, normal_sample, reset, save_model, save_source, set_bkg_model, set_full_model, set_model_autoassign_func, set_pileup_model, set_source, set_xsabund, set_xscosmo, set_xsxsect, set_xsxset, t_sample, uniform_sample
plotting
get_lrt_plot, get_lrt_results, get_pvalue_plot, get_pvalue_results, plot_cdf, plot_model, plot_model_component, plot_pdf, plot_pvalue, plot_scatter, plot_source, plot_source_component, plot_trace
psfs
delete_psf, load_conv
saving
save_delchi, save_resid
utilities
calc_chisqr, calc_energy_flux, calc_model_sum, calc_photon_flux, calc_source_sum, calc_stat
visualization
contour_model, contour_ratio, contour_resid, get_ratio, get_resid

Last modified: December 2013
Smithsonian Institute Smithsonian Institute

The Chandra X-Ray Center (CXC) is operated for NASA by the Smithsonian Astrophysical Observatory. 60 Garden Street, Cambridge, MA 02138 USA.   Email:   cxchelp@head.cfa.harvard.edu Smithsonian Institution, Copyright © 1998-2017. All rights reserved.