GODDARD HIGH-RESOLUTION SPECTROGRAPH OBSERVATIONS OF VARIABILITY IN THE RS CANUM-VENATICORUM SYSTEM V711 TAURI (HR-1099)

Goddard High Resolution Spectrograph (GHRS) observations of the RS CVn -type binary V711 Tau (K1 IV + G5 IV) were obtained at several phases over two consecutive stellar orbital cycles in order to study ultravio let emission-line profile and flux variability. Spectra cover the Mg I I h and k lines, C IV doublet, and Si IV region, as well as the densit y-sensitive lines of C III] (1909 Angstrom) and Si III] (1892 Angstrom ). IUE spectra, EUV data, and UBV photometry were obtained contemporan eously with the GHRS data. Variable extended wings were detected in th e Mg II lines. We discuss the Mg II line profile variability using var ious Gaussian emission profile models. No rotational modulation of the line profiles was observed, but there were several large flares. Thes e flares produced enhanced emission in the extended line wings, radial velocity shifts, and asymmetries in some line profiles. Nearly contin uous flaring for more than 24 hr, as indicated in the IUE data, repres ents the most energetic and long-lived chromospheric and transition re gion flare ever observed with a total energy much greater than 5 x 10( 35) ergs. The C III] to Si III] line ratio is used to estimate the pla sma density during the flares.