SPECTROPOLARIMETRY OF MAGNETIC STARS .3. MEASUREMENT UNCERTAINTIES

The estimation of the uncertainties affecting the determination of var ious parameters characterizing spectral line profiles recorded in Stok es I and V that are used in the diagnosis of stellar magnetic fields t hrough the moment technique is described. Simple statistical considera tions are presented, to demonstrate that the errors are properly asses sed and to illustrate how their evaluation can be exploited to derive information about the physical properties of the studied stars. It is shown that taking these uncertainties properly into account allows one to achieve better determination of the mean longitudinal magnetic fie ld. Improved Values of the latter are derived for observations already analysed in earlier work. The approach sketched in this paper is inte nded as a basis for future studies of magnetic fields of Ap stars.