TESS Hunt for Young and Maturing Exoplanets (THYME). III. A Two-planet System in the 400 Myr Ursa Major Group

Mann, Andrew W. and Johnson, Marshall C. and Vanderburg, Andrew and Kraus, Adam L. and Rizzuto, Aaron C. and Wood, Mackenna L. and Bush, Jonathan L. and Rockcliffe, Keighley and Newton, Elisabeth R. and Latham, David W. and Mamajek, Eric E. and Zhou, George ORCID: https://orcid.org/0000-0002-4891-3517 and Quinn, Samuel N. and Thao, Pa Chia and Benatti, Serena and Cosentino, Rosario and Desidera, Silvano and Harutyunyan, Avet and Lovis, Christophe and Mortier, Annelies and Pepe, Francesco A. and Poretti, Ennio and Wilson, Thomas G. and Kristiansen, Martti H. and Gagliano, Robert and Jacobs, Thomas and LaCourse, Daryll M. and Omohundro, Mark and Schwengeler, Hans Martin and Terentev, Ivan A. and Kane, Stephen R. and Hill, Michelle L. and Rabus, Markus and Esquerdo, Gilbert A. and Berlind, Perry and Collins, Karen A. and Murawski, Gabriel and Sallam, Nezar Hazam and Aitken, Michael M. and Massey, Bob and Ricker, George R. and Vanderspek, Roland and Seager, Sara and Winn, Joshua N. and Jenkins, Jon M. and Barclay, Thomas and Caldwell, Douglas A. and Dragomir, Diana and Doty, John P. and Glidden, Ana and Tenenbaum, Peter and Torres, Guillermo and Twicken, Joseph D. and Villanueva, Steven, Jr. (2020) TESS Hunt for Young and Maturing Exoplanets (THYME). III. A Two-planet System in the 400 Myr Ursa Major Group. The Astronomical Journal, 160 (4):179. pp. 1-18. ISSN 0004-6256

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Exoplanets can evolve significantly between birth and maturity, as their atmospheres, orbits, and structures are shaped by their environment. Young planets (<1 Gyr) offer an opportunity to probe the critical early stages of this evolution, where planets evolve the fastest. However, most of the known young planets orbit prohibitively faint stars. We present the discovery of two planets transiting HD 63433 (TOI 1726, TIC 130181866), a young Sun-like star. Through kinematics, lithium abundance, and rotation, we confirm that HD 63433 is a member of the Ursa Major moving group (τ = 414 ± 23 Myr). Based on the TESS light curve and updated stellar parameters, we estimate that the planet radii are 2.15 ± 0.10 R ⊕ and 2.67 ± 0.12 R ⊕, the orbital periods are 7.11 and 20.55 days, and the orbital eccentricities are lower than about 0.2. Using High Accuracy Radial velocity Planet Searcher for the Northern hemisphere velocities, we measure the Rossiter-McLaughlin signal of the inner planet, demonstrating that the orbit is prograde. Since the host star is bright (V = 6.9), both planets are amenable to transmission spectroscopy, radial velocity measurements of their masses, and more precise determination of the stellar obliquity. This system is therefore poised to play an important role in our understanding of planetary system evolution in the first billion years after formation.

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Item Type: Article (Commonwealth Reporting Category C)
Refereed: Yes
Item Status: Live Archive
Faculty/School / Institute/Centre: No Faculty
Faculty/School / Institute/Centre: No Faculty
Date Deposited: 14 Feb 2022 01:52
Last Modified: 14 Feb 2022 02:23
Uncontrolled Keywords: Young star clusters; Exoplanet evolution; Transits; Exoplanet; Stellar activity; Stellar rotation; Exoplanet dynamics; Astrophysics - Earth and Planetary; Astrophysics; Astrophysics - Solar and Stellar Astrophysics
Fields of Research (2008): 02 Physical Sciences > 0201 Astronomical and Space Sciences > 020110 Stellar Astronomy and Planetary Systems
Fields of Research (2020): 51 PHYSICAL SCIENCES > 5101 Astronomical sciences > 510109 Stellar astronomy and planetary systems
Socio-Economic Objectives (2008): E Expanding Knowledge > 97 Expanding Knowledge > 970102 Expanding Knowledge in the Physical Sciences
Socio-Economic Objectives (2020): 28 EXPANDING KNOWLEDGE > 2801 Expanding knowledge > 280120 Expanding knowledge in the physical sciences
Identification Number or DOI: https://doi.org/10.3847/1538-3881/abae64
URI: http://eprints.usq.edu.au/id/eprint/45008

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