The Impact of Stellar Multiplicity on Planetary Systems, I.: The Ruinous Influence of Close Binary Companions

TL;DR

This study uses high-resolution imaging to show that close binary star companions significantly reduce the likelihood of planetary system formation, with only about a third of such systems hosting planets compared to wider binaries or single stars.

Contribution

It provides the first empirical evidence quantifying how close binary companions suppress planet occurrence around solar-type stars.

Findings

Deep paucity of binary companions within 50 AU among planet-hosting stars

Planet occurrence rate in close binaries is roughly one-third that of wider binaries or single stars

Approximately 20% of solar-type stars are unlikely to host planets due to close binary influence

Abstract

The dynamical influence of binary companions is expected to profoundly influence planetary systems. However, the difficulty of identifying planets in binary systems has left the magnitude of this effect uncertain; despite numerous theoretical hurdles to their formation and survival, at least some binary systems clearly host planets. We present high-resolution imaging of 382 Kepler Objects of Interest (KOIs) obtained using adaptive-optics imaging and nonredundant aperture-mask interferometry (NRM) on the Keck-II telescope. Among the full sample of 506 candidate binary companions to KOIs, we super-resolve some binary systems to projected separations of <5 AU, showing that planets might form in these dynamically active environments. However, the full distribution of projected separations for our planet-host sample more broadly reveals a deep paucity of binary companions at solar-system scales. For a field binary population, we should have found 58 binary companions with projected separation \rho < 50 AU and mass ratio q > 0.4; we instead only found 23 companions (a 4.6 sigma deficit), many of which must be wider pairs that are only close in projection. When the binary population is parametrized with a semimajor axis cutoff a_cut and a suppression factor inside that cutoff S_bin, we find with correlated uncertainties that inside a_cut = 47 +59/-23 AU, the planet occurrence rate in binary systems is only S_bin = 0.34 +0.14/-0.15 times that of wider binaries or single stars. Our results demonstrate that a fifth of all solar-type stars in the Milky Way are disallowed from hosting planetary systems due to the influence of a binary companion.