wdem, vwdem, vvwdem: plasma emission, multi-temperature with power-law distribution of emission measure.

A multi-temperature plasma emission model built on top of the apec or mekal codes. The emission measure distribution is a powerlaw:

$$\frac{dY}{dT} = \left\{ \begin{array}{ll} 0 & {\rm if\quad} ... ...\\ 0 & {\rm if\quad} T_{max} \leq < T \\ \end{array}\right\}$$

where $Y$ is the emission measure and $c$ is chosen so that the total emission measure equals the normalization parameter (Kaastra et al. 2004).

The switch parameter determines whether the apec or mekal codes will be used. For the mekal code there are also the options to run the code for each temperature or interpolate from a pre-calculated table. The former is slower but more accurate. The mekal options are now obsolete and are only included for historical purposes. See the documentation on the apec model for additional information on using different AtomDB versions or applying thermal or velocity broadening.

For the wdem version, the abundance ratios are set by the abund command. The vwdem variant allows the user to define abundances for the more common elements while vvwdem has parameters for abundances of all elements up to Zn. See the documentation on the apec model for further information.

The parameters for wdem are:

par1	Maximum temperature for power-law emission measure distribution
par2	Ratio of minimum to maximum temperature ( $\beta = T_min/T_max$)
par3	Inverse slope ($p = 1/\alpha$)
par3	nH (cm$^{-3}$). Fixed at 1 for most applications.
par4	abundance relative to Solar
par5	redshift z
par6	switch (0 = calculate using MEKAL model; 1 = interpolate using MEKAL model; 2 = interpolate using APEC model)
norm	Normalization

For the vwdem variant the parameters are:

par1	Maximum temperature for power-law emission measure distribution
par2	Ratio of minimum to maximum temperature ( $\beta = T_min/T_max$)
par3	Inverse slope ($p = 1/\alpha$)
par4	nH (cm$^{-3}$)
par5-18	abundance for He, C, N, O, Ne, Na, Mg, Al, Si, S,Ar, Ca, Fe, Ni wrt Solar (defined by the abund command)
par19	redshift z
par20	switch (0 = calculate using MEKAL model; 1 = interpolate using MEKAL model; 2 = interpolate using APEC model)
norm	Normalization

For the vvwdem variant the parameters are:

par1	Maximum temperature for power-law emission measure distribution
par2	Ratio of minimum to maximum temperature ( $\beta = T_min/T_max$)
par3	Inverse slope ($p = 1/\alpha$)
par4	nH (cm$^{-3}$)
par5-34	abundance for H to Zn wrt Solar (defined by the abund command)
par35	redshift z
par36	switch (0 = calculate using MEKAL model; 1 = interpolate using MEKAL model; 2 = interpolate using APEC model)
norm	Normalization