TOI-5205b: A Short-period Jovian Planet Transiting a Mid-M Dwarf
Kobulnicky, Henry A.; Cochran, William D.; Mahadevan, Suvrath; Wisniewski, John; Teske, Johanna; Zeimann, Greg; Piette, Anjali A. A.; Monson, Andrew; Cañas, Caleb I.; Kanodia, Shubham; Ninan, Joe P.; Bender, Chad F.; Diddams, Scott A.; Halverson, Samuel; Metcalf, Andrew J.; Ramsey, Lawrence W.; Robertson, Paul; Roy, Arpita; Schwab, Christian; Terrien, Ryan C.; Boss, Alan; Lin, Andrea S. J.; Libby-Roberts, Jessica; Gupta, Arvind F.; Stefansson, Gudmundur; Chambers, John; Parker, Brock A.; Powers, Luke; Swaby, Tera N.; Hawley, Suzanne
United States, Switzerland, India, Australia
Abstract
We present the discovery of TOI-5205b, a transiting Jovian planet orbiting a solar metallicity M4V star, which was discovered using Transiting Exoplanet Survey Satellite photometry and then confirmed using a combination of precise radial velocities, ground-based photometry, spectra, and speckle imaging. TOI-5205b has one of the highest mass ratios for M-dwarf planets, with a mass ratio of almost 0.3%, as it orbits a host star that is just 0.392 ± 0.015 M ⊙. Its planetary radius is 1.03 ± 0.03 R J, while the mass is 1.08 ± 0.06 M J. Additionally, the large size of the planet orbiting a small star results in a transit depth of ~7%, making it one of the deepest transits of a confirmed exoplanet orbiting a main-sequence star. The large transit depth makes TOI-5205b a compelling target to probe its atmospheric properties, as a means of tracing the potential formation pathways. While there have been radial-velocity-only discoveries of giant planets around mid-M dwarfs, this is the first transiting Jupiter with a mass measurement discovered around such a low-mass host star. The high mass of TOI-5205b stretches conventional theories of planet formation and disk scaling relations that cannot easily recreate the conditions required to form such planets.