Wide companions to Hipparcos stars within 67 pc of the Sun

TL;DR

This paper presents a catalog of common-proper-motion companions to stars within 67 parsecs, analyzing their distribution, physical association probability, and implications for stellar multiplicity and companion mass ratios.

Contribution

It provides a new comprehensive catalog of CPM companions within 67 pc, estimates the fraction of physical pairs, and analyzes their separation and mass ratio distributions.

Findings

Approximately 425 physical red-dwarf companions identified.

Distribution of projected separations follows f(s) ~ s^{-1.5}.

At least 4.4% of solar-mass dwarfs have wide companions beyond 2 kAU.

Abstract

A catalog of common-proper-motion (CPM) companions to stars within 67 pc of the Sun is constructed based on the SUPERBLINK proper-motion survey. It contains 1392 CPM pairs with angular separations 30" < \rho < 1800", relative proper motion between the two components less than 25 mas/yr, 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 \"Opik'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 to 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.