logpar is a power-law with an index which varies with energy as a log parabola.
|
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 |
|
See for instance Massaro et al., 2004.