• DOI:10.3847/1538-3881/ABAE64
• Corpus ID: 218470494

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

@article{Mann2020TESSHF,
  title={TESS Hunt for Young and Maturing Exoplanets (THYME). III. A Two-planet System in the 400 Myr Ursa Major Group},
  author={Andrew W. Mann and Marshall C. Johnson and Andrew M. Vanderburg and Adam L. Kraus and Aaron C. Rizzuto and Mackenna L. Wood and Jonathan L. Bush and Keighley E. Rockcliffe and Elisabeth R. Newton and David W. Latham and Eric E. Mamajek and George Zhou and Samuel N. Quinn and Pa Chia Thao and Serena Benatti and Rosario Cosentino and Silvano Desidera and A. Harutyunyan and Christophe Lovis and Annelies Mortier and Francesco A. Pepe and Ennio Poretti and Thomas G. Wilson and Martti H. Kristiansen and Robert Gagliano and Thomas Lee Jacobs and Daryll M. LaCourse and Mark R. Omohundro and Hans M. Schwengeler and Ivan A. Terentev and Stephen R. Kane and Michelle L. Hill and Markus Rabus and Gilbert A. Esquerdo and Perry L. Berlind and Karen A. Collins and Gabriel Murawski and Nezar Hazam Sallam and Michael M. Aitken and Bob Massey and George R. Ricker and Roland K. Vanderspek and Sara Seager and Joshua N. Winn and Jon M. Jenkins and Thomas Barclay and Douglas A. Caldwell and Diana Dragomir and John P. Doty and Ana Glidden and Peter Tenenbaum and Guillermo Torres and Joseph D. Twicken and Steven Villanueva Jr},
  journal={arXiv: Earth and Planetary Astrophysics},
  year={2020}
}

• A. Mann, Marshall C. Johnson, +51 authors Steven Villanueva Jr
• Published 30 April 2020
• Physics, Geology
• arXiv: Earth and Planetary Astrophysics

Exoplanets can evolve significantly between birth and maturity, as their atmospheres, orbits, and structures are shaped by their environment. Young planets ($<$1 Gyr) offer an opportunity to probe the critical early stages of this evolution, where planets evolve the fastest. However, most of the known young planets orbit prohibitively faint stars. We present the discovery of two planets transiting HD 63433 (TOI 1726, TIC 130181866), a young Sun-like ($M_*=0.99\pm0.03$) star. Through kinematics, lithium abundance, and rotation, we confirm that HD 63433 is a member of the Ursa Major moving group ($\tau=414\pm23$ Myr). Based on the TESS light curve and updated stellar parameters, we estimate the planet radii are $2.15\pm0.10R_\oplus$ and $2.67\pm0.12R_\oplus$, the orbital periods are 7.11 and 20.55 days, and the orbital eccentricities are lower than about 0.2. Using HARPS-N 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.