Wide companions to Hipparcos stars within 67pc of the Sun

Abstract

A catalog of common-proper-motion (CPM) companions to stars within 67pc of the Sun is constructed based on the SUPERBLINK proper-motion survey. It contains 1392 CPM pairs with angular separations 30″ < ρ < 1800″, relative proper motion between the two components less than 25masyr -1, and magnitudes and colors of the secondaries consistent with those of dwarfs in the (M V , V - J) diagram. In addition, we list 21 candidate white dwarf CPM companions with separations under 300″, about half of which should be physical. We estimate a 0.31 fraction of pairs with red dwarf companions to be physical systems (about 425 objects), while the rest (mostly wide pairs) are chance alignments. For each candidate companion, the probability of a physical association is evaluated. The distribution of projected separations s of the physical pairs between 2 kAU and 64 kAU follows f(s)s -1.5, which decreases faster than Öpik's law. We find that solar-mass dwarfs have no less than 4.4% ± 0.3% companions with separations larger than 2 kAU, or 3.8% ± 0.3% per decade of orbital separation in the 2-16 kAU range. The distribution of mass ratio of those wide companions is approximately uniform in the 0.1 < q < 1.0 range, although we observe a dip at q ≃ 0.5 which, if confirmed, could be evidence of bimodal distribution of companion masses. New physical CPM companions to two exoplanet host stars are discovered. © 2012. The American Astronomical Society. All rights reserved.