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Judith Korth



A planetary system with two transiting mini-Neptunes near the radius valley transition around the bright M dwarf TOI-776


  • R. Luque
  • L. M. Serrano
  • K. Molaverdikhani
  • M. C. Nixon
  • J. H. Livingston
  • E. W. Guenther
  • E. Pallé
  • N. Madhusudhan
  • G. Nowak
  • J. Korth
  • W. D. Cochran
  • T. Hirano
  • P. Chaturvedi
  • E. Goffo
  • S. Albrecht
  • O. Barragán
  • C. Briceño
  • J. Cabrera
  • D. Charbonneau
  • R. Cloutier
  • K. A. Collins
  • K. I. Collins
  • K. D. Colón
  • I. J.M. Crossfield
  • Sz Csizmadia
  • F. Dai
  • H. J. Deeg
  • M. Esposito
  • M. Fridlund
  • D. Gandolfi
  • I. Georgieva
  • A. Glidden
  • R. F. Goeke
  • S. Grziwa
  • A. P. Hatzes
  • C. E. Henze
  • S. B. Howell
  • J. Irwin
  • J. M. Jenkins
  • E. L.N. Jensen
  • P. Kábath
  • R. C. Kidwell
  • J. F. Kielkopf
  • E. Knudstrup
  • K. W.F. Lam
  • D. W. Latham
  • J. J. Lissauer
  • A. W. Mann
  • E. C. Matthews
  • I. Mireles
  • N. Narita
  • M. Paegert
  • C. M. Persson
  • S. Redfield
  • G. R. Ricker
  • F. Rodler
  • J. E. Schlieder
  • N. J. Scott
  • S. Seager
  • J. Šubjak
  • T. G. Tan
  • E. B. Ting
  • R. Vanderspek
  • V. Van Eylen
  • J. N. Winn
  • C. Ziegler

Summary, in English

We report the discovery and characterization of two transiting planets around the bright M1 V star LP 961-53 (TOI-776, J = 8.5 mag, M = 0.54 ± 0.03 M⊙) detected during Sector 10 observations of the Transiting Exoplanet Survey Satellite (TESS). Combining the TESS photometry with HARPS radial velocities, as well as ground-based follow-up transit observations from the MEarth and LCOGT telescopes, for the inner planet, TOI-776 b, we measured a period of Pb = 8.25 d, a radius of Rb = 1.85 ± 0.13 R⊙, and a mass of Mb = 4.0 ± 0.9 M⊙; and for the outer planet, TOI-776 c, a period of Pc = 15.66 d, a radius of Rc = 2.02 ± 0.14 R⊙, and a mass of Mc = 5.3 ± 1.8 M⊙. The Doppler data shows one additional signal, with a period of ~34 d, associated with the rotational period of the star. The analysis of fifteen years of ground-based photometric monitoring data and the inspection of different spectral line indicators confirm this assumption. The bulk densities of TOI-776 b and c allow for a wide range of possible interior and atmospheric compositions. However, both planets have retained a significant atmosphere, with slightly different envelope mass fractions. Thanks to their location near the radius gap for M dwarfs, we can start to explore the mechanism(s) responsible for the radius valley emergence around low-mass stars as compared to solar-like stars. While a larger sample of well-characterized planets in this parameter space is still needed to draw firm conclusions, we tentatively estimate that the stellar mass below which thermally-driven mass loss is no longer the main formation pathway for sculpting the radius valley is between 0.63 and 0.54 M⊙. Due to the brightness of the star, the TOI-776 system is also an excellent target for the James Webb Space Telescope, providing a remarkable laboratory in which to break the degeneracy in planetary interior models and to test formation and evolution theories of small planets around low-mass stars.

Publishing year





Astronomy and Astrophysics



Document type

Journal article


EDP Sciences


  • Planetary systems
  • Stars: individual: LP 961-53
  • Stars: low-mass
  • Techniques: photometric
  • Techniques: radial velocities




  • ISSN: 0004-6361