A Far Ultraviolet Spectroscopic Survey of Luminous Cool Stars

FUSE ultraviolet spectra of 8 giant and supergiant stars reveal that high temperature (3×10K) atmospheres are common in luminous cool stars and extend across the color-magnitude diagram from α Car (F0 II) to the cool giant α Tau (K5 III). Emission present in these spectra includes chromospheric H-Lyβ, Fe II, C I, and transition region lines of C III, O VI, Si III, Si IV. Emission lines of Fe XVIII and Fe XIX signaling temperatures of ∼10K and coronal material are found in the most active stars, β Cet and 31 Com. A short-term flux variation, perhaps a flare, was detected in β Cet during our observation. Stellar surface fluxes of the emission of C III and O VI are correlated and decrease Currently at Rutherford Appleton Laboratory, Culham UK Currently at McDonald Observatory, University of Texas, Austin, TX 78712-1083