Last modified: December 2020

URL: https://cxc.cfa.harvard.edu/sherpa/ahelp/set_pileup_model.html
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AHELP for CIAO 4.13 Sherpa v1

set_pileup_model

Context: modeling

Synopsis

Include a model of the Chandra ACIS pile up when fitting PHA data.

Syntax

set_pileup_model(id, model=None)

id - int or str, optional
model - an instance of the jdpileup class

Description

Chandra observations of bright sources can be affected by pileup, so that there is a non-linear correlation between the source model and the predicted counts. This process can be modelled by including the `jdpileup` model for a data set, using the `set_pileup_model` .


Example

Plot up the model (an xsphabs model multiplied by a powlaw1d component) and then overplot the same expression but including the effects of pile up in the Chandra ACIS instrument:

>>> load_pha('src.pi')
>>> set_source(xsphabs.gal * powlaw1d.pl)
>>> plot_model()
>>> set_pileup_model(jdpileup.jpd)
>>> plot_model(overplot=True)

PARAMETERS

The parameters for this function are:

Parameter Definition
id The data set containing the source expression. If not given then the default identifier is used, as returned by `get_default_id` .
model

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 `model` parameter. If given two un-named arguments, then they are interpreted as the `id` and `model` parameters, respectively.

This is a generic function, and can be used to model other non-linear detector effects, but at present the only available model is for the ACIS pile up provided by the jdpileup model.


Bugs

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

See Also

confidence
set_conf_opt, set_covar_opt, set_proj_opt
data
get_bkg_chisqr_plot, get_bkg_delchi_plot, get_bkg_fit_plot, get_bkg_model_plot, get_bkg_plot, get_bkg_ratio_plot, get_bkg_resid_plot, get_bkg_source_plot, set_areascal, set_arf, set_backscal, set_bkg, set_coord, set_counts, set_data, set_dep, set_exposure, set_grouping, set_quality, set_rmf, set_staterror, set_syserror
filtering
set_filter
info
list_model_ids, list_pileup_model_ids, show_bkg_model, show_bkg_source
methods
set_iter_method, set_iter_method_opt, set_method, set_method_opt
model
delete_pileup_model
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_num_par_frozen, get_num_par_thawed, get_order_plot, get_par, get_pileup_model, get_source, get_source_component_image, get_source_component_plot, get_source_contour, get_source_image, get_source_plot, get_xsabund, get_xscosmo, get_xsxsect, get_xsxset, image_model, image_model_component, image_source, image_source_component, integrate, link, load_table_model, load_template_interpolator, load_template_model, load_user_model, normal_sample, reset, save_model, save_source, set_bkg_model, set_bkg_source, set_full_model, set_model, set_model_autoassign_func, set_par, set_source, set_xsabund, set_xscosmo, set_xsxsect, set_xsxset, t_sample, uniform_sample
plotting
get_cdf_plot, get_pdf_plot, 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
statistics
set_prior, set_sampler, set_sampler_opt, set_stat
utilities
calc_chisqr, calc_energy_flux, calc_model_sum, calc_photon_flux, calc_source_sum, calc_stat, eqwidth, set_analysis, set_default_id
visualization
contour_model, contour_ratio, contour_resid, image_setregion