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Description
Based on the Hipparcos and Tycho-2 astrometric catalogs and the ROSAT surveys, a sample of ~100 stars most luminous in X-rays within or around a distance of 50 pc is culled. The smallest X-ray luminosity in the sample is LX=9.8x10^29^erg/s; the strongest source in the solar neighborhood is II Peg, a RS CVn star, at LX=175.8x10^29^erg/s. With respect to the origin of X-ray emission, the sample is divided into partly overlapping classes of pre-main-sequence, post-T Tauri, and very young ZAMS objects (type XY), RS CVn-type binary stars (type RS), other active short-period binaries, including binary BY Dra-type objects (type XO), apparently single or long-period binary active evolved stars (type XG), contact binaries of WU UMa kind (type WU), apparently single or long-period binary variable stars of BY Dra kind (type BY), and objects of unknown nature (type X?). Chromospherically active, short-period binaries (RS and XO) make up 40% of the brightest X-ray emitters, followed by young stars (XY) at 30% and unknown sources (X?) at 15%.
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