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Last modified: 26 October 2016

URL: http://cxc.harvard.edu/sherpa/models/index.html

Sherpa Models

Sherpa | Sherpa (optical) | XSPEC | Other

The models available in Sherpa are listed below. The full list may be accessed within Sherpa using the list_models() command.


Sherpa models


Sherpa optical models

The following Sherpa models are designed for use with spectra or SEDs at optical wavelengths, which means that where relevant, position, line width, and other similar model parameters have units of Angstroms.


Models from XSPEC

Sherpa includes the "additive" and "multiplicative" models of XSpec version 12.9.0d. The XSpec model names have the prefix "xs", e.g. XSpec phabs model is called "xsphabs"; see "ahelp xs" for general information on the XSpec models in Sherpa.

The tablemodel model mentioned below can be used to read in XSPEC table models.

Missing model

The nlapec model from XSPEC 12.9.0 is not available in Sherpa 4.8. It can be emulated by taking advantage of the APECNOLINES xset option:

[The first version of the model evaluation includes the line emission (e.g. a nump of emission around 1 keV) whereas the second time it is displayed it has no lines.]
[Print media version: The first version of the model evaluation includes the line emission (e.g. a nump of emission around 1 keV) whereas the second time it is displayed it has no lines.]

Removing line emission from APEC models

sherpa> set_source(xsphabs.gal * xsapec.src)
sherpa> gal.nh = 0.05
sherpa> plot_source()
sherpa> set_curve(['*.color', 'default'])
sherpa> log_scale()
sherpa> set_xsxset('APECNOLINES', 'on')
sherpa> plot_source(overplot=True)
sherpa> set_curve(['line.style', 'dot'])

Other models

Models can also be created using Python code with the commands load_user_model and add_user_pars, or the add_model function which is used to add a model class to Sherpa (in which case the model behaves like the in-built Sherpa models.


Last modified: 26 October 2016
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