Searching for Giant Exoplanets around M-dwarf Stars (GEMS) I: Survey Motivation
Shubham Kanodia, Caleb I. Cañas, Suvrath Mahadevan, Eric B. Ford, Ravit Helled, Dana E. Anderson, Alan Boss, William D. Cochran, Megan Delamer, Te Han, Jessica E. Libby-Roberts, Andrea S. J. Lin, Simon Müller, Paul Robertson, Guðmundur Stefánsson, Johanna Teske
TL;DR
This work tackles the rarity and formation of giant exoplanets around M-dwarfs (GEMS) and the tension with core-accretion theory. It synthesizes existing GEMS data from transit, RV, microlensing, and disk observations to establish the observational baseline and motivate a targeted survey. The authors introduce the Searching for GEMS survey, employing multi-dimensional nonparametric statistics and Monte-Carlo simulations to forecast the survey size and mass-measurement precision needed to compare GEMS bulk densities with those of canonical hot-Jupiters around FGK stars, estimating a requirement of roughly $40$ transiting GEMS with $5$-$\sigma$ mass measurements (versus $\sim 15$ currently known). They also discuss limitations of current occurrence-rate estimates and outline a systematic plan to improve them, guiding future surveys and informing planet-formation theory about GEMS demographics and properties.
Abstract
Recent discoveries of transiting giant exoplanets around M-dwarf stars (GEMS), aided by the all-sky coverage of TESS, are starting to stretch theories of planet formation through the core-accretion scenario. Recent upper limits on their occurrence suggest that they decrease with lower stellar masses, with fewer GEMS around lower-mass stars compared to solar-type. In this paper, we discuss existing GEMS both through confirmed planets, as well as protoplanetary disk observations, and a combination of tests to reconcile these with theoretical predictions. We then introduce the \textit{Searching for GEMS} survey, where we utilize multi-dimensional nonparameteric statistics to simulate hypothetical survey scenarios to predict the required sample size of transiting GEMS with mass measurements to robustly compare their bulk-density with canonical hot-Jupiters orbiting FGK stars. Our Monte-Carlo simulations predict that a robust comparison requires about 40 transiting GEMS (compared to the existing sample of $\sim$ 15) with 5-$σ$ mass measurements. Furthermore, we discuss the limitations of existing occurrence estimates for GEMS, and provide a brief description of our planned systematic search to improve the occurrence rate estimates for GEMS.