Do not allow indicated model parameters to vary. (See also thaw.)
XSPEC> freeze [<param range>...]
where <param range> =:: {<param #> | <param #>-<param #>}. The indicated model parameter or range of model parameters will be marked so they cannot be varied by the fit command by setting their associated <delta> to less than zero (see newpar command). By default, the range will be the last range input by either a freeze or thaw command.