TESS Hunt for Young and Maturing Exoplanets (THYME). X. A Two-planet System in the 210 Myr MELANGE-5 Association

July 2024 • 2024AJ....168...41T

Authors • Thao, Pa Chia • Mann, Andrew W. • Barber, Madyson G. • Kraus, Adam L. • Tofflemire, Benjamin M. • Bush, Jonathan L. • Wood, Mackenna L. • Collins, Karen A. • Vanderburg, Andrew • Quinn, Samuel N. • Zhou, George • Newton, Elisabeth R. • Ziegler, Carl • Law, Nicholas • Barkaoui, Khalid • Pozuelos, Francisco J. • Timmermans, Mathilde • Gillon, Michaël • Jehin, Emmanuël • Schwarz, Richard P. • Gan, Tianjun • Shporer, Avi • Horne, Keith • Sefako, Ramotholo • Suarez, Olga • Mekarnia, Djamel • Guillot, Tristan • Abe, Lyu • Triaud, Amaury H. M. J. • Radford, Don J. • Lopez Murillo, Ana Isabel • Ricker, George R. • Winn, Joshua N. • Jenkins, Jon M. • Bouma, Luke G. • Fausnaugh, Michael • Guerrero, Natalia M. • Kunimoto, Michelle

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.

Links

• PREPRINT http://arxiv.org/abs/2406.05234
• ELECTR https://doi.org/10.3847/1538-3881/ad4993
• SIMBAD https://simbad.u-strasbg.fr/simbad/sim-ref?querymethod=bib&simbo=on&submit=submit+bibcode&bibcode=2024AJ....168...41T
• PDF https://iopscience.iop.org/article/10.3847/1538-3881/ad4993/pdf
• DATA https://archive.stsci.edu/mastbibref.php?bibcode=2024AJ....168...41T
• DATA https://irsa.ipac.caltech.edu/bibdata/2024/T/2024AJ....168...41T.html