load_arf

sherpa.astro.ui.load_arf(id, arg=None, resp_id=None, bkg_id=None)

Load an ARF from a file and add it to a PHA data set.

Load in the effective area curve for a PHA data set, or its background. The load_bkg_arf function can be used for setting most background ARFs.

Parameters:
  • id (int or str, optional) – The data set to use. If not given then the default identifier is used, as returned by get_default_id.
  • arg – Identify the ARF: a file name, or a data structure representing the data to use, as used by the I/O backend in use by Sherpa: a TABLECrate for crates, as used by CIAO, or a list of AstroPy HDU objects.
  • resp_id (int or str, optional) – The identifier for the ARF within this data set, if there are multiple responses.
  • bkg_id (int or str, optional) – Set this to identify the ARF as being for use with the background.

See also

get_arf()
Return the ARF associated with a PHA data set.
load_bkg_arf()
Load an ARF from a file and add it to the background of a PHA data set.
load_multi_arfs()
Load multiple ARFs for a PHA data set.
load_pha()
Load a file as a PHA data set.
load_rmf()
Load a RMF from a file and add it to a PHA data set.
set_full_model()
Define the convolved model expression for a data set.
set_arf()
Set the ARF for use by a PHA data set.
unpack_arf()
Create an ARF data structure.

Notes

The function does not follow the normal Python standards for parameter use, since it is designed for easy interactive use. When called with a single un-named argument, it is taken to be the arg parameter. If given two un-named arguments, then they are interpreted as the id and arg parameters, respectively. The remaining parameters are expected to be given as named arguments.

If a PHA data set has an associated ARF - either from when the data was loaded or explicitly with the set_arf function - then the model fit to the data will include the efect of the ARF when the model is created with set_model or set_source. In this case the get_source function returns the user model, and get_model the model that is fit to the data (i.e. it includes any response information; that is the ARF and RMF, if set). To include the ARF explicitly, use set_full_model.

The minimum_energy setting of the ogip section of the Sherpa configuration file determines the behavior when an ARF with a minimum energy of 0 is read in. The default is to replace the 0 by the value 1e-10, which will also cause a warning message to be displayed.

Examples

Use the contents of the file ‘src.arf’ as the ARF for the default data set.

>>> load_arf('src.arf')

Read in an ARF from the file ‘bkg.arf’ and set it as the ARF for the background model of data set “core”:

>>> load_arf('core', 'bkg.arf', bkg_id=1)