An emission spectrum from hot diffuse gas based on the model calculations of Mewe and Kaastra with Fe L calculations by Liedahl. The model includes line emissions from several elements. The switch parameter determines whether the mekal code will be run to calculate the model spectrum for each temperature or whether the model spectrum will be interpolated from a precalculated table. The former is slower but more accurate. Relative abundances are set by the abund command for the mekal model. The vmekal variant allows the user to set the individual abundances for the model.
par1 
plasma temperature in keV 
par2 
H density (cm^{3}) 
par3 
Metal abundance (He fixed at cosmic). The elements included are C, N, O, Ne, Na, Mg, Al, Si, S, Ar, Ca, Fe, Ni. 
par4 
(fixed) redshift 
Par5 
0 calculate 
1 interpolate 

2 interpolate using APEC model 

norm 
_{} where D_{A} is the angular diameter distance to the source (cm), and n_{e ,} n_{H} (cm^{3}) are the electron and hydrogen densities respectively. 
Parameters for the vmekal variant are:
par1 
plasma temperature in keV 
par2 
H density (cm^{3}) 
par3par16 
Abundances for He, C, N, O, Ne, Na, Mg, Al, Si, S, Ar, Ca, Fe, Ni wrt Solar (given by the Anders & Grevesse mixture) 
par17 
(fixed) redshift 
par18 
0 calculate 
1 interpolate 

2 interpolate using APEC model 

norm 
_{} where D_{A} is the angular diameter distance to the source (cm), and n_{e ,} n_{H} (cm^{3}) are the electron and hydrogen densities respectively. 
The references for the MEKAL model are as follows :
Mewe, R., Gronenschild, E.H.B.M., and van den Oord, G.H.J. 1985,A&AS, 62, 197
Mewe, R., Lemen, J.R., and van den Oord, G.H.J. 1986, A&AS}, 65, 511
Kaastra, J.S. 1992, An XRay Spectral Code for Optically Thin Plasmas (Internal SRONLeiden Report, updated version 2.0)
Liedahl, D.A., Osterheld, A.L., and Goldstein, W.H. 1995, ApJL, 438, 115
Similar acknowledgement may also be given for the adopted ionization balance:
Arnaud, M., and Rothenflug, M. 1985, A&AS, 60, 425
Arnaud, M., and Raymond, J. 1992, ApJ, 398, 394