... models.^5.1

The majority of the models in XSPEC are 1-D, created to fit energy spectra (in units of keV). Therefore the user must exercise caution when combining models from the Sherpa and XSPEC libraries$-$the models must be a function of the same arguments. For instance, data may be input to Sherpa with any units, so if the user wishes to combine models, the data should be defined in keV, or the user should supply an instrument model that provides a mapping from the observed units to keV. Instrument models are discussed later in this chapter.

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... response,^5.2

$R$ may include contributions that are defined in separate Response Matrix Format [RMF] and Ancillary Response Format [ARF] files. [NEED REFERENCE HERE.]

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... values.^5.3

Parameter prompting can be turned off using the command PARAMPROMPT OFF.

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