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

parameters
offset a	slope b
-1.20923e-05	0.000687465

Covariance matrix
1.23739e-12	-5.22054e-11
-5.22054e-11	2.23879e-09

used data points for fitting
energy [keV]	efficiency	efficiency error	nuclide
53.15	1.53576e-05	7.9858e-07	Ba133
80.99	3.5681e-06	1.43817e-07	Ba133
