TESS Hunt for Young and Maturing Exoplanets (THYME). X. A Two-planet System in the 210 Myr MELANGE-5 Association
Pa Chia Thao, Andrew W. Mann, Madyson G. Barber, Adam L. Kraus, Benjamin M. Tofflemire, Jonathan L. Bush, Mackenna L. Wood, Karen A. Collins, Andrew Vanderburg, Samuel N. Quinn, George Zhou, Elisabeth Newton, Carl Ziegler, Nicholas M. Law, Khalid Barkaoui, F. J. Pozuelos, Mathilde Timmermans, M. Gillon, Emmanuël Jehin, Richard P. Schwarz, Tianjun Gan, Avi Shporer, K. Horne, Ramotholo Sefako, Olga Suárez, D. Mékarnia, T. Guillot, Lyu Abe, A. H. M. J. Triaud, Don J. Radford, Ana Isabel Lopez Murillo, G. Ricker, Joshua N. Winn, Jon M. Jenkins, Luke G. Bouma, Michael Fausnaugh, Natalia Guerrero, Michelle Kunimoto
Abstract
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.