Primordial Circumstellar Disks in Binary Systems: Evidence for Reduced Lifetimes

TL;DR

This study shows that binary star systems with closer separations tend to lose their circumstellar disks faster, impacting planet formation theories in multiple star systems.

Contribution

It provides the first statistically significant evidence linking binary separation to the presence and lifetime of circumstellar disks.

Findings

Systems with separations < 40 AU are half as likely to have disks.

Significant difference in disk presence between close and wider binaries.

Implications for planet formation in multiple star systems.

Abstract

We combine the results from several multiplicity surveys of pre-main-sequence stars located in four nearby star-forming regions with Spitzer data from three different Legacy Projects. This allows us to construct a sample of 349 targets, including 125 binaries, which we use to to investigate the effect of companions on the evolution of circumstellar disks. We find that the distribution of projected separations of systems with Spitzer excesses is significantly different (P ~2.4e-5, according to the KS test for binaries with separations < 400 AU) from that of systems lacking evidence for a disk. As expected, systems with projected separations < 40 AU are half as likely to retain at least one disk than are systems with projected separations in the 40-400 AU range. These results represent the first statistically significant evidence for a correlation between binary separation and the presence of an inner disk (r ~ 1 AU). Several factors (e.g., the incompleteness of the census of close binaries, the use of unresolved disk indicators, and projection effects) have previously masked this correlation in smaller samples. We discuss the implications of our findings for circumstellar disk lifetimes and the formation of planets in multiple systems.