Study of spectral and polarimetric variability of the AE Herbig star AB Aur.

Results are presented of H-alpha spectral observations and wideband polarimetry of the Ae-Herbig star AB Aur with well defined P-Cyg-type profiles of the Balmer lines. The slow (from season to season) and the rapid (from night to night) AB Aur variabilities are discussed. It is shown that the main characteristics of spectral and polarimetric variations can be explained within the framework of the stellar wind model with a sector inhomogeneity that is due to local magnetic fields on the stellar surface. The best agreement between the observational and theoretical profiles of the H-alpha emission line is achieved when the model of the envelope with a magnetosphere is used with an average surface magnetic field value of between 0 and 200 G.