Investigating Large Planet Candidates Around M Dwarf Stars

The Transiting Exoplanet Survey Satellite (TESS) monitors stars to detect small dips in their light from transiting exoplanets. M dwarf stars (R < 0.7 R_sun, T_eff < 4000 K were observed in great numbers by TESS and most exoplanets found around M dwarf stars are small, ranging from the size of Earth to the size of Neptune. Exoplanets with radii similar to Jupiter or larger (> 11 Earth radii) are rare, with only 5 Jupiter sized planets transiting M dwarf stars confirmed so far. In order to increase our understanding of these giant exoplanets, more candidates need to be found and confirmed. In this study we identified all giant planet candidates (> 5 Earth radii) transiting M dwarfs in the TESS Object of Interest (TOI) sample from Sectors 1 through Y (not sure what the latest sector was). We then used the Python package Lightkurve to make diagnostic images and light curves for each target to further investigate the planet candidates and identify any interesting features in the light curve. Interesting features included flares, star spots, and clear transits. Once the most interesting candidates were identified, further analysis was completed by investigating additional vetting documents and observations in the ExoFOP database. Using the additional observations and vetting documents, any candidate that could have been an eclipsing binary system or a false positive was removed from the giant planet candidate sample. This procedure was followed for 52 M dwarf giant exoplanet candidates. Out of these 52 candidates, 28 held up to further analysis and diagnostics. Several interesting systems were determined within this list of 28 candidates. These interesting systems included a compelling 9 Earth radius candidate, a triple star system that potentially hosts a planet, and a system that shows a stellar flare and star-spots in addition to a planet transit. These candidates are prime targets for confirmation as exoplanets via continued observations. Any newly confirmed giant planets transiting M dwarfs from the TESS sample will greatly improve our understanding of planet demographics and occurrence rates. This research was partially supported through Embry-Riddle Aeronautical University’s Faculty Innovative Research in Science and Technology (FIRST) Program.