Three Very Metal-Poor, Extremely Wide Binaries

Abstract

In a recent investigation [1] we have identified over a hundred wide, common proper-motion binaries belonging to the old disk, the thick disk or the halo of the Galaxy. These systems were found by searching for common propermotion companions to the high-velocity, metal-poor primaries of the lists of Schuster et al. [3,4]. For these stars, Strömgren photometry has allowed the determination of metallicities, distances and, in many cases, individual ages. The values obtained for the metallicities and ages of a number of these stars place them among the oldest, most metal-poor stars of the Galaxy. For the purposes of this work, we concentrate our attention on those stars with [Fe/H] < -2.00 as representatives of the very early stellar population of our Galaxy.