Chandra X-Ray Observatory
Skip to the navigation links
Last modified: December 2013

Jump to: Description · Examples · Bugs · See Also

AHELP for CIAO 4.9 Sherpa v1


Context: data


Load a source or background ARF


load_arf( [id], filename|ARFCrate, [resp_id=1], [bkg_id=None] )


The load_arf command loads an ARF (effective area) from a FITS file or an ARFCrate. The ARF may be set as the response file for any available source or background dataset. Additionally, more than one ARF may be associated with a dataset.

  • 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")
  • filename|ARFCrate - the name of the file (with path) or ARFCrate which contains the ARF data
  • resp_id - the id of the response, if multiple responses exist for the dataset; default is id=1
  • bkg_id - the id of the background, if the response is a background response; default=None

The load_bkg_arf command ("ahelp load_bkg_arf") may instead be used to load the background ARF. It uses the default background and response ids, which is adequate for most simple analysis sessions.

Example 1

sherpa> load_arf("arf.fits")

Load arf.fits and assign it as the first ARF for the source dataset. This basic case could also have been done with the load_bkg_arf command ("ahelp load_bkg_arf")

Example 2

sherpa> load_arf(1, "source.arf", resp_id=2)

The file source.arf is loaded as the second ARF (the resp_id is 2) assigned to the dataset with id=1.

Example 3

sherpa> load_arf("arf.fits", resp_id=1, bkg_id=2)

Load a background response on the second background (bkg_id=2) of a PHA data set. The ARF is loaded from a file and uses the default dataset id.

Example 4

sherpa> arfcr = read_arf("3c273.arf")
sherpa> load_arf(arfcr)

The ARF is read into an ARFCrate (named "arfcr") from the file 3c273.arf. The ARF is then loaded into Sherpa from the crate, using the default options.


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

See Also

dataspace1d, dataspace2d, datastack, fake, get_arf, get_bkg, load_arrays, load_ascii, load_bkg, load_bkg_arf, load_bkg_rmf, load_data, load_grouping, load_image, load_multi_arfs, load_multi_rmfs, load_pha, load_quality, load_rmf, load_staterror, load_syserror, load_table, pack_image, pack_pha, pack_table, set_arf, unpack_arf, unpack_arrays, unpack_ascii, unpack_bkg, unpack_data, unpack_image, unpack_pha, unpack_rmf, unpack_table
get_default_id, list_bkg_ids, list_data_ids, list_response_ids
add_model, add_user_pars, get_response, load_table_model, load_template_model, load_user_model, save_model, save_source
save_arrays, save_data, save_delchi, save_error, save_filter, save_grouping, save_image, save_pha, save_quality, save_resid, save_staterror, save_syserror, save_table

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: Smithsonian Institution, Copyright © 1998-2017. All rights reserved.