1999A&A...344..221G

High-resolution spectra of the RS CVn system AR Lac taken during total eclipse of the primary component lead to a precise determination of the stellar effective temperature of the secondary, T_eff=5100±100K, and a surface gravity logg=3.65±0.1. The small-scale motions are well represented by a microturbulence velocity of v_t=1.6±0.3km/s. Examination of a number of spectral windows by means of spectrum synthesis based on solar spectrum reference fits produces a pattern of photospheric metal abundances that is essentially represented by solar or slightly enhanced values. This is at variance with the subsolar metal abundances reported from X-ray observations with the ROSAT and ASCA satellites. The effective temperature determined here restricts the surface fraction of cool matter such as confined in star spots during the present observations to values around 0.3. For a close binary system with an active chromosphere the photospheric spectra are normal. No spectrum variations on a half hour time scale are detected.