Binaries Among Debris Disk Stars

TL;DR

This study investigates the prevalence and characteristics of binary companions among debris disk stars, revealing fewer binaries than expected and suggesting that intermediate separations often clear out disks, affecting planet formation.

Contribution

It provides new adaptive optics observations identifying a previously unknown binary companion and analyzes the binary fraction and separation distribution among debris disk stars.

Findings

25% of debris disk stars are in binary or multiple systems

Binary systems with 1-100 AU separations are less common than expected

Disk luminosity tends to be lower in multiple star systems

Abstract

We have gathered a sample of 112 main-sequence stars with known debris disks. We collected published information and performed adaptive optics observations at Lick Observatory to determine if these debris disks are associated with binary or multiple stars. We discovered a previously unknown M-star companion to HD 1051 at a projected separation of 628 AU. We found that 25+/-4% of our debris disk systems are binary or triple star systems, substantially less than the expected ~50%. The period distribution for these suggests a relative lack of systems with 1-100 AU separations. Only a few systems have blackbody disk radii comparable to the binary/triple separation. Together, these two characteristics suggest that binaries with intermediate separations of 1-100 AU readily clear out their disks. We find that the fractional disk luminosity, as a proxy for disk mass, is generally lower for multiple systems than for single stars at any given age. Hence, for a binary to possess a disk (or form planets) it must either be a very widely separated binary with disk particles orbiting a single star or it must be a small separation binary with a circumbinary disk.