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

Mann, Andrew W. and Wood, Mackenna L. and Schmidt, Stephen P. and Barber, Madyson G. and Owen, James E. and Tofflemire, Benjamin M. and Newton, Elisabeth R. and Mamajek, Eric E. and Bush, Jonathan L. and Mace, Gregory N. and Kraus, Adam L. and Thao, Pa Chia and Vanderburg, Andrew and Llama, Joe and Johns-Krull, Christopher M. and Prato, L. and Stahl, Asa G. and Tang, Shih-Yun and Fields, Matthew J. and Collins, Karen A. and Collins, Kevin I. and Gan, Tianjun and Jensen, Eric L. N. and Kamler, Jacob and Schwarz, Richard P. and Furlan, Elise and Gnilka, Crystal L. and Howell, Steve B. and Lester, Kathryn V. and Owens, Dylan A. and Suarez, Olga and Mekarnia, Djamel and Guillot, Tristan and Abe, Lyu and Triaud, Amaury H. M. J. and Johnson, Marshall C. and Milburn, Reilly P. and Rizzuto, Aaron C. and Quinn, Samuel N. and Kerr, Ronan and Ricker, George R. and Vanderspek, Roland and Latham, David W. and Seager, Sara and Winn, Joshua N. and Jenkins, Jon M. and Guerrero, Natalia M. and Shporer, Avi and Schlieder, Joshua E. and McLean, Brian and Wohler, Bill (2022) TESS Hunt for Young and Maturing Exoplanets (THYME). VI. An 11 Myr Giant Planet Transiting a Very-low-mass Star in Lower Centaurus Crux. Astronomical Journal, 163 (4). Art. No. 156. ISSN 0004-6256. doi:10.3847/1538-3881/ac511d.

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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.

Item Type:Article
Related URLs:
URLURL TypeDescription Paper
Mann, Andrew W.0000-0003-3654-1602
Wood, Mackenna L.0000-0001-7336-7725
Owen, James E.0000-0002-4856-7837
Tofflemire, Benjamin M.0000-0003-2053-0749
Newton, Elisabeth R.0000-0003-4150-841X
Mamajek, Eric E.0000-0003-2008-1488
Mace, Gregory N.0000-0001-7875-6391
Kraus, Adam L.0000-0001-9811-568X
Thao, Pa Chia0000-0001-5729-6576
Vanderburg, Andrew0000-0001-7246-5438
Llama, Joe0000-0003-4450-0368
Johns-Krull, Christopher M.0000-0002-8828-6386
Prato, L.0000-0001-7998-226X
Stahl, Asa G.0000-0002-0848-6960
Tang, Shih-Yun0000-0003-4247-1401
Collins, Karen A.0000-0001-6588-9574
Collins, Kevin I.0000-0003-2781-3207
Gan, Tianjun0000-0002-4503-9705
Jensen, Eric L. N.0000-0002-4625-7333
Schwarz, Richard P.0000-0001-8227-1020
Furlan, Elise0000-0001-9800-6248
Gnilka, Crystal L.0000-0003-2519-6161
Howell, Steve B.0000-0002-2532-2853
Lester, Kathryn V.0000-0002-9903-9911
Suarez, Olga0000-0002-3503-3617
Mekarnia, Djamel0000-0001-5000-7292
Guillot, Tristan0000-0002-7188-8428
Abe, Lyu0000-0002-0856-4527
Triaud, Amaury H. M. J.0000-0002-5510-8751
Johnson, Marshall C.0000-0002-5099-8185
Rizzuto, Aaron C.0000-0001-9982-1332
Quinn, Samuel N.0000-0002-8964-8377
Kerr, Ronan0000-0002-6549-9792
Ricker, George R.0000-0003-2058-6662
Vanderspek, Roland0000-0001-6763-6562
Latham, David W.0000-0001-9911-7388
Seager, Sara0000-0002-6892-6948
Winn, Joshua N.0000-0002-4265-047X
Jenkins, Jon M.0000-0002-4715-9460
Guerrero, Natalia M.0000-0002-5169-9427
Shporer, Avi0000-0002-1836-3120
Schlieder, Joshua E.0000-0001-5347-7062
McLean, Brian0000-0002-8058-643X
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 (, 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 ( 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), (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).
Group:Infrared Processing and Analysis Center (IPAC)
Funding AgencyGrant Number
Heising-Simons Foundation2019-1490
NSF Graduate Research FellowshipDGE-1650116
North Carolina Space Grant ConsortiumUNSPECIFIED
University of North Carolina at Chapel HillUNSPECIFIED
European Research Council (ERC)853022
Heising-Simons Foundation51 Pegasi b Fellowship
Mt. Cuba Astronomical FoundationUNSPECIFIED
McDonald ObservatoryUNSPECIFIED
Korea Astronomy and Space Science Institute (KASI)UNSPECIFIED
Gaia Multilateral AgreementUNSPECIFIED
European Research Council (ERC)803193
Science and Technology Facilities Council (STFC)ST/S00193X/1
Engineering and Physical Sciences Research Council (EPSRC)EP/P020259/1
Subject Keywords:Pre-main sequence stars; Transits; Exoplanet evolution; Exoplanet formation; Stellar associations; Stellar ages; OB associations; Time domain astronomy; Time series analysis; Late-type stars; Low mass stars
Issue or Number:4
Classification Code:Unified Astronomy Thesaurus concepts: Pre-main sequence stars (1290); Transits (1711); Exoplanet evolution (491); Exoplanet formation (492); Stellar associations (1582); Stellar ages (1581); OB associations (1140); Time domain astronomy (2109); Time serie
Record Number:CaltechAUTHORS:20220309-982406000
Persistent URL:
Official Citation:Andrew W. Mann et al 2022 AJ 163 156
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:113813
Deposited By: George Porter
Deposited On:09 Mar 2022 23:17
Last Modified:09 Mar 2022 23:17

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