Stellar images derived from rotation broadening - AW Ursae Majoris

Abstract

New spectroscopic observations of the W UMa star AW Ursae Majoris are interpreted by retrieving the star's continuum Doppler redistribution function through the Fourier deconvolution of broadened strong lines by a standard flux profile, and the star's shape and surface brightness distribution are derived. The graphical approach to rotation broadening is briefly reviewed, and the implicit assumptions are stated. The observations and data reduction method are described, and the assumption that the locally emitted spectral profile is uniform over the stellar surface is examined. The Doppler redistribution functions obtained for AW UMa are consistently too narrow and asymmetric for the assumed geometry of the system. It is concluded that a large fraction of the primary component is covered with a solarlike plage centered on the side away from the secondary, which radically alters the local line equivalent widths.