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

Creators: 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; THYME Collaboration

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.

Additional Information

© 2022. The American Astronomical Society. Original content from this work may be used under the terms of the Creative Commons Attribution 4.0 licence. Any further distribution of this work must maintain attribution to the author(s) and the title of the work, journal citation and DOI. Received 2021 October 18; revised 2021 December 28; accepted 2022 January 20; published 2022 March 9. The authors thank the anonymous referee for providing insightful comments and suggestions on the paper. A.W.M. would like to thank Bandit, who sat directly on A.W.M.'s keyboard whenever MISTTBORN was running, preventing him from working on this manuscript too much. The THYME collaboration also wants to thank Halee, Wally, Maizie, Dudley, Charlie, Marley, and Edmund for their thoughtful discussions and emotional support. A.W.M. was supported through NASA's Astrophysics Data Analysis Program (80NSSC19K0583), a grant from the Heising-Simons Foundation (2019–1490), and the TESS GI program (80NSSC21K1054). M.L.W. was supported by a grant through NASA's K2 GO program (80NSSC19K0097). M.J.F. was supported by NASA's Exoplanet Research Program (XRP; 80NSSC21K0393). This material is based on work supported by the National Science Foundation Graduate Research Fellowship Program under grant No. DGE-1650116 to P.C.T. M.J.F. and R.P.M. were supported by the NC Space Grant Graduate Research program. M.G.B. and S.P.S. were supported by the NC Space Grant Undergraduate Research program. M.G.B. was also supported by funding from the Chancellors Science Scholars Program at the University of North Carolina at Chapel Hill. J.E.O. is supported by a Royal Society University Research Fellowship, and this project has received funding from the European Research Council (ERC) under the European Unions Horizon 2020 research and innovation program (grant agreement No. 853022, PEVAP). A.C.R. was supported as a 51 Pegasi b Fellow through the Heising-Simons Foundation. E.R.N. acknowledges support from the TESS GI program (program G03141). Based on observations collected at the European Organisation for Astronomical Research in the Southern Hemisphere under ESO programs 0101.A-9012(A), 0101.C-0527(A), 0101.C-0902(A), 081.C-0779(A), 082.C-0390(A), 094.C-0805(A), 098.C-0739(A), and 60.A-9022(C). This work used the Immersion Grating Infrared Spectrometer (IGRINS) that was developed under a collaboration between the University of Texas at Austin and the Korea Astronomy and Space Science Institute (KASI) with the financial support of the Mt. Cuba Astronomical Foundation, of the US National Science Foundation under grants AST-1229522 and AST-1702267, of the McDonald Observatory of the University of Texas at Austin, of the Korean GMT Project of KASI, and of Gemini Observatory. This paper includes data collected by the TESS mission, which are publicly available from the Mikulski Archive for Space Telescopes (MAST). Funding for the TESS mission is provided by NASA's Science Mission Directorate. This research has made use of the Exoplanet Follow-up Observation Program website, which is operated by the California Institute of Technology, under contract with the National Aeronautics and Space Administration under the Exoplanet Exploration Program. This work has made use of data from the European Space Agency (ESA) mission Gaia, 47 processed by the Gaia Data Processing and Analysis Consortium (DPAC). 48 Funding for the DPAC has been provided by national institutions, in particular the institutions participating in the Gaia Multilateral Agreement. This work makes use of observations from the LCOGT network. Part of the LCOGT telescope time was granted by NOIRLab through the Mid-Scale Innovations Program (MSIP). MSIP is funded by NSF. This research received funding from the European Research Council (ERC) under the European Union's Horizon 2020 research and innovation program (grant agreement No. 803193/BEBOP) and from the Science and Technology Facilities Council (STFC; grant No. ST/S00193X/1). This research has made use of the VizieR catalog access tool, CDS, Strasbourg, France. The original description of the VizieR service was published in A&AS 143, 23. Resources supporting this work were provided by the NASA High-End Computing (HEC) Program through the NASA Advanced Supercomputing (NAS) Division at Ames Research Center for the production of the SPOC data products. We acknowledge the use of public TOI Release data from pipelines at the TESS Science Office and at the TESS Science Processing Operations Center. We acknowledge the use of public TESS data from pipelines at the TESS Science Office and at the TESS Science Processing Operations Center. Part of this research was carried out at the Jet Propulsion Laboratory, California Institute of Technology, under a contract with the National Aeronautics and Space Administration (NASA). Part of this work was performed using resources provided by the Cambridge Service for Data Driven Discovery (CSD3) operated by the University of Cambridge Research Computing Service (www.csd3.cam.ac.uk), provided by Dell EMC and Intel using Tier-2 funding from the Engineering and Physical Sciences Research Council (capital grant EP/P020259/1), and DiRAC funding from the Science and Technology Facilities Council (www.dirac.ac.uk). Based on observations obtained at the international Gemini Observatory, a program of NSF's NOIRLab, which is managed by the Association of Universities for Research in Astronomy (AURA) under a cooperative agreement with the National Science Foundation, on behalf of the Gemini Observatory partnership: the National Science Foundation (United States), National Research Council (Canada), Agencia Nacional de Investigación y Desarrollo (Chile), Ministerio de Ciencia, Tecnología e Innovación (Argentina), Ministério da Ciência, Tecnologia, Inovações e Comunicações (Brazil), and Korea Astronomy and Space Science Institute (Republic of Korea). Facilities: Exoplanet Archive - , LCOGT 1 m (Sinistro) - , SOAR (Goodman) - , SALT (HRS) - , Gemini (IGRINS) - , TESS - , ASTEP - . Software: MISTTBORN (Johnson et al. 2018), IGRINS RV (Stahl et al. 2021), emcee (Foreman-Mackey et al. 2013), batman (Kreidberg 2015), matplotlib (Hunter 2007), corner.py (Foreman-Mackey 2016), AstroImageJ (Collins et al. 2017), BANZAI (McCully et al. 2018), TAPIR (Jensen 2013), saphires (Tofflemire et al. 2019), TelFit (Gullikson et al. 2014), BANYAN-Σ (Gagné et al. 2018), unpopular (Hattori et al. 2021), synphot (Lim 1919), MOLUSC (Wood et al. 2021), FriendFinder (Tofflemire et al. 2021).

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