The Ruinous Impact of Close Binaries on Planetary Systems

The majority of searches for extrasolar planets have concentrated
exclusively on single stars, avoiding close binary systems where the
companion might complicate the observations and analysis. However, the
majority of solar-type stars have binary companions, and they should
exert a strong dynamical influence on any planetary system. I will
discuss new discoveries that outline the influence of stellar
multiplicity at different stages of planet formation and evolution,
enabled by a high-resolution imaging technique (nonredundant
aperture-mask interferometry) that opens the discovery space for
binary companions on solar-system scales (5-50 AU) even around
relatively distant stars (100-500 pc). First, I will summarize the
results of a combined multiplicity and disk census of 1-10 Myr old
stars in several star-forming regions. These results demonstrate the
ruinous effect of close binary companions upon protoplanetary disks;
at ages when disks are still ubiquitous among single stars and wide
binaries, the corresponding disk fraction among close binaries is
suppressed by a factor of 3-4. I will then describe an ongoing program
to study the multiplicity of Kepler planet host stars, for which my
results indicate that the planet occurrence rate is similarly
suppressed among close binaries. Finally, I will discuss how these
results change the interpretation of planet formation and disk
dissipation around single stars, given that almost all of them appear
to host disks for at least 2-3 Myr, and what this might mean for the
timescales and mass budgets for assembling planetary systems.