SURFACE IMAGING OF LATE-TYPE CONTACT BINARIES .1. AE-PHOENICIS AND YY-ERIDANI

This paper presents the results of the first application of Doppler Im aging to solar-type contact binaries. Our aim was to examine whether t his technique can help discriminate between various types of surface i nhomogeneities (dark vs. bright star-spots) which are produced by diff erent physical processes and which affect not only the surface brightn ess distribution but also the system's secular evolution. Simultaneous high dispersion spectroscopy and photometry for the systems AE Phe an d YY Eri were obtained at ESO using the Coude Auxiliary Telescope (CAT ) and the 50 cm telescope. The observed light-curves were solved by me ans of the latest version of the Wilson-Devinney program. Doppler maps were constructed taking into account the effects of fast rotation and proximity of the system's components. Doppler maps reveal the presenc e of dark spots on both systems. For AE Phe, this result is in agreeme nt with the light-curve solution. Indirect evidence of enhanced chromo spheric emission is also found. This emission appears to be more inten se on the primary components.