Comparing the Architectures of Multiplanet Systems from Kepler, K2, and TESS Data

Abstract

Exoplanet surveys like Kepler, TESS, and K2 have shown that planetary systems are common in our galaxy. These surveys, along with several others, have identified thousands of planetary candidates, with more than five thousand having already been confirmed. Many of these planetary systems host multiple planets. As we discover more multiplanet systems, notable trends begin to appear in the data. We use kernel density estimation (KDE) to analyze the period ratios of adjacent planet pairs in multiplanet systems in the most recent Kepler, TESS and K2 data, paying particular attention to pairs in first order mean motion resonance (MMR). We compare a recent Kepler catalog with the DR25 data release. We also compare TESS and K2 against this recently released Kepler data. To verify the significance of our findings against selection bias, we perform Monte Carlo simulations of multiplanet systems in the TESS catalog, finding an excess of planet pairs near the 2 (2:1), and 1.5 (3:2) period ratios, both exceeding the 99\% confidence interval. We also find a significant peak at the 2.19 period ratio, which exceeds the 90\% confidence interval. Using a lower limit for period ratios determined by the period of the inner planet proposed in Steffen & Farr (2013), we identify two planet pairs orbiting M dwarf stars in a very tight ratio. We also note a likely misidentified planet pair orbiting an FGK type star, which if further study proves to be true, would indicate that only planets orbiting M dwarf stars may violate this limit.