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04/25/19: SO/NOAO Joint Colloquium Series: Adam Kraus, Univ. of Texas


Title: The Impact of Stellar Multiplicity on Planetary Systems

Most 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 form with binary companions, and they should profoundly sculpt the formation and evolution of planetary systems. I will discuss statistically robust samples 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. However, some planetary systems do survive even in very dynamically perilous configurations, and I will outline the factors that potentially contribute to planetary survival and destruction. 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.

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