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Choose Your Own Adventure: Multiplicity of Planets among the Kepler M Dwarfs

Date: Wed. November 12th, 2014, 11:00 am-1:00 am
Location: Sears 552

Choose Your Own Adventure: Multiplicity of Planets among the Kepler M Dwarfs

Sarah Ballard, University of Washington

The Kepler data set has furnished more than 130 exoplanetary candidates orbiting M dwarf hosts, nearly half of which reside in multiply transiting systems. I investigate the proposition of self-similarity in this sample, first posited by Swift et al. (2013) for the analysis of the five-planet system orbiting the small star Kepler-32. If we compare the predictions of one single mode of planet multiplicity and coplanarity against the Kepler sample, we can test whether we replicate the multi-planet yield of Kepler. If every M dwarf hosts 5 or more planets, with small mutual inclinations, we recover Kepler’s planet return for systems with two or more transiting planets. However, the number of singly-transiting systems remains too high to be consistent with this proposition, even accounting for a higher false positive rate among systems exhibiting only one periodic transit. The data much prefer a model with two distinct modes of planet formation around M dwarfs, one quiescent and one violent, which occur in roughly equal measure. I investigate astrophysical explanations for this feature of Kepler’s multiple planet population orbiting small stars, and discuss the relative unlikelihood of selection bias or unusually high false positive rates as an explanation. By folding in recent analyses about planet multiplicity versus eccentricity, I conclude with a description of how this two-mode model informs our search for habitable worlds.

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