4.1.12. Dem: differential emission measure model¶
This model calculates a set of isothermal CIE spectra, that can be used
later in one of the DEM analysis tools (see the “dem” commands of the
syntax). The CIE spectra are evaluated for a logarithmic grid of
temperatures between 
and 
, with 
bins.
Warning
For the DEM methods to work, the dem model is the only allowed additive component that can be present. No other additive components are allowed. But of course the spectrum of the dem model may be modified by applying any combination of multiplicative models (redshifts, absorptions, line broadening, etc.).
Warning
Because of the above, do not use the fit commands when
you have a dem model. If you really need to fit, use the pdem model
(Pdem: DEM models) instead.
Warning
In general, the spacing between the different temperature
components should not be smaller than 0.10 in 
. Smaller
step sizes will produce unstable solutions.
The parameters of the model are:
t1 : Lower temperature in keV. Default value: 0.001
keV.t2 : Upper temperature in keV. Default value: 100 keV.nr : Number of temperature bins. Default value: 64.hden : Hydrogen density in 
.it : Ion temperature in keV.vrms : RMS Velocity broadening in km/s (see Definition of the micro-turbulent velocity in SPEX).ref : Reference element.01...30 : Abundances of H to Zn.file : Filename for the non-thermal electron distribution.Recommended citation: Mewe et al. (1995)
