Abstract
ABSTRACT The three X-ray selected mid-K stars with the highest values of (fx/fv) in the Einstein Medium Sensitivity Survey have been studied spectroscopically at moderate and high spectral resolution. One of these objects (1E1548.7+1125) is presented as a binary-star system with characteristics similar to the RS CVn class of binaries. A second of these stars (1E1751.0+7046) is a rapid rotator, while the third star (1E1339.9+6030) has not been shown to be either a binary system or a rapid rotator. The presence of both Ca II H and K emission core and high X-ray flux is attributed to chromospheric and coronal activity, but no single underlying cause is indicated.
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