TESS Hunt for Young and Maturing Exoplanets (THYME). VI. An 11 Myr Giant Planet Transiting a Very-low-mass Star in Lower Centaurus Crux

April 2022 • 2022AJ....163..156M

Authors • Mann, Andrew W. • Wood, Mackenna L. • Schmidt, Stephen P. • Barber, Madyson G. • Owen, James E. • Tofflemire, Benjamin M. • Newton, Elisabeth R. • Mamajek, Eric E. • Bush, Jonathan L. • Mace, Gregory N. • Kraus, Adam L. • Thao, Pa Chia • Vanderburg, Andrew • Llama, Joe • Johns-Krull, Christopher M. • Prato, L. • Stahl, Asa G. • Tang, Shih-Yun • Fields, Matthew J. • Collins, Karen A. • Collins, Kevin I. • Gan, Tianjun • Jensen, Eric L. N. • Kamler, Jacob • Schwarz, Richard P. • Furlan, Elise • Gnilka, Crystal L. • Howell, Steve B. • Lester, Kathryn V. • Owens, Dylan A. • Suarez, Olga • Mekarnia, Djamel • Guillot, Tristan • Abe, Lyu • Triaud, Amaury H. M. J. • Johnson, Marshall C. • Milburn, Reilly P. • Rizzuto, Aaron C. • Quinn, Samuel N. • Kerr, Ronan • Ricker, George R. • Vanderspek, Roland • Latham, David W. • Seager, Sara • Winn, Joshua N. • Jenkins, Jon M. • Guerrero, Natalia M. • Shporer, Avi • Schlieder, Joshua E. • McLean, Brian • Wohler, Bill

Abstract • Mature super-Earths and sub-Neptunes are predicted to be ≃ Jovian radius when younger than 10 Myr. Thus, we expect to find 5-15 R _⊕ planets around young stars even if their older counterparts harbor none. We report the discovery and validation of TOI 1227b, a 0.85 ± 0.05 R _J (9.5 R _⊕) planet transiting a very-low-mass star (0.170 ± 0.015 M _⊙) every 27.4 days. TOI 1227's kinematics and strong lithium absorption confirm that it is a member of a previously discovered subgroup in the Lower Centaurus Crux OB association, which we designate the Musca group. We derive an age of 11 ± 2 Myr for Musca, based on lithium, rotation, and the color-magnitude diagram of Musca members. The TESS data and ground-based follow-up show a deep (2.5%) transit. We use multiwavelength transit observations and radial velocities from the IGRINS spectrograph to validate the signal as planetary in nature, and we obtain an upper limit on the planet mass of ≃0.5 M _J. Because such large planets are exceptionally rare around mature low-mass stars, we suggest that TOI 1227b is still contracting and will eventually turn into one of the more common <5 R _⊕ planets.

Links

• PREPRINT http://arxiv.org/abs/2110.09531
• ELECTR https://doi.org/10.3847/1538-3881/ac511d
• SIMBAD http://simbad.u-strasbg.fr/simbo.pl?bibcode=2022AJ....163..156M
• PDF https://iopscience.iop.org/article/10.3847/1538-3881/ac511d/pdf
• DATA http://cdsarc.cds.unistra.fr/viz-bin/cat/J/AJ/163/156
• DATA http://archive.eso.org/bin/ads2eso?2022AJ....163..156M
• DATA https://archive.gemini.edu/searchform/publication=2022AJ....163..156M
• DATA https://irsa.ipac.caltech.edu/bibdata/2022/M/2022AJ....163..156M.html