TOI-5205b: A Short-period Jovian Planet Transiting a Mid-M Dwarf
Shubham Kanodia, Suvrath Mahadevan, Jessica E. Libby-Roberts, Guðmundur Stefánsson, Caleb I. Cañas, Anjali A. A. Piette, Alan P. Boss, Johanna Teske, John Chambers, Greg Zeimann, Andrew Monson, Paul Robertson, Joe P. Ninan, Andrea S. J. Lin, Chad F. Bender, William D. Cochran, Scott A. Diddams, Arvind F. Gupta, Samuel Halverson, Suzanne L. Hawley, Henry A. Kobulnicky, Andrew J. Metcalf, Brock A. Parker, Luke Powers, Lawrence W. Ramsey, Arpita Roy, Christian Schwab, Tera N. Swaby, Ryan C. Terrien, John P. Wisniewski
Abstract
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.