A SEARCH FOR CHROMOSPHERICALLY ACTIVE STARS FROM THE ROSAT EUV SOURCE LIST

Optical spectroscopic observations have been made of ten G-, K-, and M-type stars which were detected as EUV sources by the ROSAT Wide Field Camera (WFC). The optical spectra reveal the signatures of enhanced chromospheric activity in nine of the ten stars. Halpha appears as a partially filled absorption line in seven of nine stars observed in that region and is strongly in emission in two, HD 160934 and Wolf 1225. The strongest line of the Ca II infrared triplet (8542 angstrom) appears as a partially filled absorption line in five of the six stars observed in that region. Two stars with filled Halpha and Ca II 8542 angstrom lines (BD+48 3686 and HD 171488) were also observed to have a strong Li absorption line at 6707 angstrom, suggesting an age less than the age of the Pleiades (7 X 10(7) yr). Two stars were discovered to be double-lined spectroscopic binaries (BD+27 3245 and HD 144110). This work has also identified a previously unreported chromospherically active star with a very strong level of activity, HD 160934.