The Distribution of Fe, Cr, and Si over the Surface of θ Aur

Abstract

Very accurate spectroscopic line profiles have been obtained at various phases during the 3 ^d_. 618 period of the magnetic variable Ap-star θ Aur. These profiles were observed using a Reticon detector at the coudé focus of the 3.5 metre Canada-France-Hawaii telescope. The mapping of Si, Cr and Fe over the surface of the star was done by solving the Inverse Problem. Complex spotty structure has been revealed with the number of Fe spots found being as great as six. The distribution of Cr is found to be similar to Fe but with less detailed structure. Si is distributed quite differently from Fe and Cr. Discussion of the relationship of the magnetic field maximum phase and the light curve along with the maps of the distribution of elements suggests that the principal spots of Fe and Cr are in phase with the light variability but they are 90° out of phase with Si and the magnetic field variation. We are surprised by the Si variability seeming to be 90° out of phase with the light variability.