LINEAR POLARIMETRY OF AP STARS .3. A DIAGNOSTIC METHOD FOR THE MAGNETIC-STRUCTURE OF ROTATING STARS

A method for the diagnostic of magnetic fields in Ap stars is presente d. It is based on the joint interpretation of traditional circular pol arization observations (giving B-1, the longitudinal magnetic field av eraged over the stellar surface) and of broadband linear polarization observations. The method consists in a numerical, best-fit algorithm w hich takes into account the possibility of describing the time variati on of broadband linear polarization by means of analytical expressions . The algorithm has been checked against numerical simulations and has shown to be reliable especially for the determination of the magnetic configuration of the star. Two applications have been considered for the stars HD 24712 and HD 71866 by interpreting new broadband linear p olarization observations together with circular polarization data avai lable in the literature.