Planetary Science Seminar

The Kepler mission has revealed that most stars host at least one planet. We also know that almost half of stellar systems in the solar neighborhood belong to multiple-star systems. Thus, binarity must be considered if we are to characterize and understand as an ensemble the known exoplanets and exoplanet candidates. First, I will discuss why companions to exoplanet host stars can be a "bane" to exoplanet astronomers. Kepler transiting planet candidates rely on spectroscopic and imaging follow-up observations to rule out false positives and detect blended stars; such observations can change measured planet radii, and even rule out planetary status. Traditionally the two techniques have probed different host star companion parameters spaces, but how well, and under what conditions, do the planet host companion parameters derived from the two techniques agree? I will discuss some of my recent work addressing why we really need both types of observations to validate Kepler planets. Second, I will explain why companions to exoplanet host stars can be a "boon" to exoplanet astronomers. While initially suggested as a sign of accretion of H-depleted material onto the star, the giant planet-metallicity correlation is now established as a mostly primordial effect -- stellar composition affects planet formation. But is it still possible that planet formation may also influence host star composition? Previous studies hinted at a few cases of compositional differences between stars in binary systems, and now high-precision abundance analyses are exploring this possibility in systems known to host planets. I will discuss the important role binary host stars have to play in extending correlations between stellar composition and the presence/type of planets that form, including the case of a newly-detected "extreme" exoplanet system.