TESS Hunt for Young and Maturing Exoplanets (THYME). X. A Two-planet System in the 210 Myr MELANGE-5 Association
Vanderburg, Andrew; Triaud, Amaury H. M. J.; Quinn, Samuel N.; Zhou, George; Horne, Keith; Ziegler, Carl; Collins, Karen A.; Ricker, George R.; Winn, Joshua N.; Jenkins, Jon M.; Kraus, Adam L.; Barkaoui, Khalid; Guillot, Tristan; Abe, Lyu; Suarez, Olga; Shporer, Avi; Barber, Madyson G.; Mann, Andrew W.; Gillon, Michaël; Pozuelos, Francisco J.; Fausnaugh, Michael; Gan, Tianjun; Jehin, Emmanuël; Sefako, Ramotholo; Kunimoto, Michelle; Bouma, Luke G.; Schwarz, Richard P.; Law, Nicholas; Newton, Elisabeth R.; Tofflemire, Benjamin M.; Wood, Mackenna L.; Thao, Pa Chia; Radford, Don J.; Timmermans, Mathilde; Guerrero, Natalia M.; Mekarnia, Djamel; Bush, Jonathan L.; Lopez Murillo, Ana Isabel
United States, Australia, Belgium, Spain, China, United Kingdom, South Africa, France
Abstract
Young (<500 Myr) planets are critical to studying how planets form and evolve. Among these young planetary systems, multiplanet configurations are particularly useful, as they provide a means to control for variables within a system. Here, we report the discovery and characterization of a young planetary system, TOI-1224. We show that the planet host resides within a young population we denote as MELANGE-5. By employing a range of age-dating methods—isochrone fitting, lithium abundance analysis, gyrochronology, and Gaia excess variability—we estimate the age of MELANGE-5 to be 210 ± 27 Myr. MELANGE-5 is situated in close proximity to previously identified younger (80–110 Myr) associations, Crius 221 and Theia 424/Volans-Carina, motivating further work to map out the group boundaries. In addition to a planet candidate detected by the TESS pipeline and alerted as a TESS object of interest, TOI-1224 b, we identify a second planet, TOI-1224 c, using custom search tools optimized for young stars (Notch and LOCoR). We find that the planets are 2.10 ± 0.09 R ⊕ and 2.88 ± 0.10 R ⊕ and orbit their host star every 4.18 and 17.95 days, respectively. With their bright (K = 9.1 mag), small (R * = 0.44 R ⊙), and cool (T eff = 3326 K) host star, these planets represent excellent candidates for atmospheric characterization with JWST.