IUE observations of the RS CVn systems Z Her, TY Pyx and HD 155555.

Abstract

Short wavelength (λλ1150 - 1950 Å) low resolution ultraviolet spectra of three RS CVn regular-period binary systems, obtained with the IUE satellite, have been examined. Newly observed spectra were compared with those retrieved from the IUE data bank. The surface fluxes of chromospheric and transition region lines were obtained and are briefly discussed. The enhancements relative to the quiet sun were derived; they increase with the line formation temperature and in all cases are higher than those found among single active stars.