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Judith Korth



HD 191939 revisited : New and refined planet mass determinations, and a new planet in the habitable zone


  • J. Orell-Miquel
  • G. Nowak
  • F. Murgas
  • E. Palle
  • G. Morello
  • R. Luque
  • M. Badenas-Agusti
  • I. Ribas
  • M. Lafarga
  • N. Espinoza
  • J. C. Morales
  • M. Zechmeister
  • A. Alqasim
  • W. D. Cochran
  • D. Gandolfi
  • E. Goffo
  • P. Kabáth
  • J. Korth
  • K. W. F. Lam
  • J. Livingston
  • A. Muresan
  • C. M. Persson
  • V. Van Eylen

Summary, in English

HD 191939 (TOI-1339) is a nearby (d = 54 pc), bright (V = 9
mag), and inactive Sun-like star (G9 V) known to host a multi-planet
transiting system. Ground-based spectroscopic observations confirmed the
planetary nature of the three transiting sub-Neptunes (HD 191939 b, c,
and d) originally detected by TESS and were used to measure the masses
for planets b and c with 3σ precision. These previous observations also
reported the discovery of an additional Saturn-mass planet (HD 191939 e)
and evidence for a further, very long-period companion (HD 191939 f).
Here, we report the discovery of a new non-transiting planet in the
system and a refined mass determination of HD 191939 d. The new planet,
HD 191939 g, has a minimum mass of 13.5±2.0 M and a
period of about 280 days. This period places the planet within the
conservative habitable zone of the host star, and near a 1:3 resonance
with HD 191939 e. The compilation of 362 radial velocity measurements
with a baseline of 677 days from four different high-resolution
spectrographs also allowed us to refine the properties of the previously
known planets, including a 4.6σ mass determination for planet d, for which only a 2σ
upper limit had been set until now. We confirm the previously suspected
low density of HD 191939 d, which makes it an attractive target for
attempting atmospheric characterisation. Overall, the planetary system
consists of three sub-Neptunes interior to a Saturn-mass and a
Uranus-mass planet plus a high-mass long-period companion. This
particular configuration has no counterpart in the literature and makes
HD 191939 an exceptional multi-planet transiting system with an unusual
planet demographic worthy of future observation.

Publishing year





Astronomy and Astrophysics



Document type

Journal article


EDP Sciences


  • Astronomy, Astrophysics and Cosmology


  • Planets and satellites: individual: HD 191939 d
  • Planets and satellites: individual: HD 191939 g
  • Stars: individual: HD 191939
  • Techniques: photometric
  • Techniques: radial velocities




  • ISSN: 0004-6361