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

parameters
offset a	slope b
-3.41922e-05	0.00191726

Covariance matrix
1.25425e-11	-5.27142e-10
-5.27142e-10	2.25415e-08

used data points for fitting
energy [keV]	efficiency	efficiency error	nuclide
53.16	4.24543e-05	2.53385e-06	Ba133
81	9.54115e-06	4.71723e-07	Ba133
