X-RAY SOURCES IN REGIONS OF STAR-FORMATION .6. THE R-CRA ASSOCIATION AS VIEWED BY EINSTEIN

We report an optical identifications of X-ray sources in the vicinity of the R CrA association. We identify 11 low-mass pre-main-sequence st ars as counterparts of 9 X-ray sources. We also find X-ray emission fr om coordinates consistent with the position of 3 bright late-B stars, although the emission may come from lower mass companions. The X-ray-s elected stars lie along a narrow locus in the luminosity-temperature d iagram at an age of about 7 Myr, which is considerably older than the estimated ages of the higher mass stars or of the IR-excess stars. We determine the physical characteristics of these stars, including masse s, ages, and Lithium abundances. We estimate that the complete members hip of the R CrA association amounts to about 90 stars, mostly older n aked T Tauri stars, and that the population is consistent with the sta ndard IMF. (C) 1997 American Astronomical Society.