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logpar, zlogpar: log-parabolic blazar model

logpar is a power-law with an index which varies with energy as a log parabola. The zlogpar variant computes a redshifted spectrum. See for instance Massaro et al. (2004).

$\displaystyle A(E) = K (E/pivotE)^{(-a-b\log{(E/pivotE)})} $

par1 a, slope at the pivot energy
par2 b, curvature term
par3 pivotE, fixed pivot energy (best near low end of energy range).
norm= K  

For zlogpar the formula and corresponding parameters are:

$\displaystyle A(E) = K ([E(1+z)]/pivotE)^{(-a-b\log{([E(1+z)]/pivotE)})} $

par1 a, slope at the pivot energy
par2 b, curvature term
par3 pivotE, fixed pivot energy (best near low end of energy range).
par4 z, redshift
norm= K