Abstract
Previous work has established the enhanced occurrence of compact systems of multiple small exoplanets around metal-poor stars. In this talk I will investigate whether the radii distribution between single- and multi-transiting planets are consistent with being drawn from the same underlying planetary population. We construct a planetary sample of 290 Kepler-derived planets orbiting late-K and M-dwarfs containing 149 planets from single-transiting planetary systems and 141 planets from multi-transiting compact multiple planetary systems (54 compact multiples). We perform two-sample Kolmogorov-Smirnov tests, Mann-Whitney U tests, and Anderson-Darling k-sampling tests on the radius distributions of our two samples and find statistical evidence (p < 0.0026) that planets in compact multiple systems are larger, on average, than their single-transiting counterparts. In this talk I will also discuss whether this effect could originate via more efficient outgassing of a secondary atmosphere in compact multiple systems due to the stress and strain forces of interplanetary tides, and the amounts of volatiles required in the bulk mantle to account for this result. We discuss the implications that our result has on planet formation theories, including the possibility that the planet formation channels for single-transiting and compact multiple planets are different and result in different interior compositions of these planetary populations.