Used file for the fit: SDD_normalized-Efficiency_point-source_with-air_all-levels.csv

parameters
offset a	slope b
-4.39408e-06	0.000246806

Covariance matrix
1.43045e-13	-6.07043e-12
-6.07043e-12	2.61327e-10

used data points for fitting
energy [keV]	efficiency	efficiency error	nuclide
53.16	5.44737e-06	2.72846e-07	Ba133
80.98	1.22365e-06	4.5725e-08	Ba133
