An X-ray sampling of nearby stars.

Einstein (HEAO 2) observations of stars within 6.5 pc are reported with much reference to optical information. The detected stars are +43°44 AB, η Eri, Ross 47, +44°2051 AB, Wolf 630 AB, VB8, 70 Oph AB, δ Pav, -36°13540 AB, 61 Cyg AB, and Krüger 60 AB. Other stars observed with upper limits of X-ray flux density are τ Cet, 82 Eri, LP 658-2, AC +79°3888, and Wolf 629. The sample includes a white dwarf, an old subdwarf, a_giant, and dG-dM, dMe stars in various age groups. Two out of four objects that contain optical flare stars appear to flare in X-rays within 2 × 10³ s of observation, but several objects that do not flare optically have not similarly flared in X-rays. Stellar X-ray luminosity is shown coordinated with B - v, V, and photospheric luminosity L. The stars Wolf 630 AB, η Eri, and 70 Oph AB are exceptionally luminous in X-rays, but no controlling parameter for X-ray production or deficiency has been isolated.