expcheb6, vexpcheb6, bexpcheb6, bvexpcheb6: differential emission measure using exponential of a 6-order Chebyshev polynomial

expcheb6 is a multi-temperature collisional-ionization equilibrium model using the exponential of a sixth-order Chebyshev polynomial for the differential emission measure. The switch parameter determines whether spectrum is calculated by running the mekal code, by interpolating on a pre-calculated mekal table, using the AtomDB data, or using the SPEX data. The final two options is now preferred. See the cie model for further information and options. The reference for this model is Singh et al. (1996, ApJ, 456, 766).

Velocity broadening can only be used with switch=2.

For expcheb6 the parameters are:

par1–6	Chebyshev polynomial coefficients
par7	H density (cm$^{-3}$)
par8	abundance wrt to Solar
par9	Redshift
par10	Switch (0 = calculate using mekal model, 1 = interpolate using mekal model, 2 = use AtomDB data, 3 = use SPEX data).
norm	Normalization

For vexpcheb6 the parameters are:

par1–6	Chebyshev polynomial coefficients
par7	H density (cm$^{-3}$)
par8–21	Abundances of He, C, N, O, Ne, Na, Mg, Al, Si, S, Ar, Ca, Fe, Ni wrt Solar (defined by the abund command)
par22	Redshift
par23	Switch (0 = calculate using mekal model, 1 = interpolate using mekal model, 2 = use AtomDB data, 3 = use SPEX data).
norm	Normalization

For bexpcheb6 the parameters are:

par1–6	Chebyshev polynomial coefficients
par7	H density (cm$^{-3}$)
par8	abundance wrt to Solar
par9	Redshift
par10	Gaussian sigma for velocity broadening (km/s) (switch=2 or 3 only)
par11	Switch (0 = calculate using mekal model, 1 = interpolate using mekal model, 2 = use AtomDB data, 3 = use SPEX data).
norm	Normalization

For bvexpcheb6 the parameters are:

par1–6	Chebyshev polynomial coefficients
par7	H density (cm$^{-3}$)
par8–21	Abundances of He, C, N, O, Ne, Na, Mg, Al, Si, S, Ar, Ca, Fe, Ni wrt Solar (defined by the abund command)
par22	Redshift
par23	Gaussian sigma for velocity broadening (km/s) (switch=2 or 3 only)
par24	Switch (0 = calculate using mekal model, 1 = interpolate using mekal model, 2 = use AtomDB data, 3 = use SPEX data).
norm	Normalization

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