HD 191939 revisited: New and refined planet mass determinations, and a new planet in the habitable zone
Journal article, 2023
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 3Ï 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 4.6Ï mass determination for planet d, for which only a 2Ï 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.
Planets and satellites: individual: HD 191939 d
Stars: individual: HD 191939
Planets and satellites: individual: HD 191939 g
Techniques: photometric
Techniques: radial velocities
Author
J. Orell-Miquel
Instituto de Astrofísica de Canarias
University of La Laguna
G. Nowak
Instituto de Astrofísica de Canarias
University of La Laguna
F. Murgas
University of La Laguna
Instituto de Astrofísica de Canarias
E. Palle
University of La Laguna
Instituto de Astrofísica de Canarias
Giuseppe Morello
Instituto de Astrofísica de Canarias
University of La Laguna
R. Luque
Spanish National Research Council (CSIC)
University of Chicago
M. Badenas-Agusti
Massachusetts Institute of Technology (MIT)
I. Ribas
Centre Tecnològic de Telecomunicacions de Catalunya (CTTC)
Spanish National Research Council (CSIC)
Marina Lafarga
The University of Warwick
Néstor Espinoza
Max Planck Society
J. C. Morales
Centre Tecnològic de Telecomunicacions de Catalunya (CTTC)
Spanish National Research Council (CSIC)
M. Zechmeister
University of Göttingen
A. Alqasim
University College London (UCL)
W. D. Cochran
Center for Planetary Systems Habitability
The University of Texas at Austin
D. Gandolfi
University of Turin
E. Goffo
University of Turin
Thüringer Landessternwarte Tautenburg
Petr Kabath
Czech Academy of Sciences
Judith Korth
Chalmers, Space, Earth and Environment, Astronomy and Plasmaphysics
K. W.F. Lam
German Aerospace Center (DLR)
J. Livingston
National Astronomical Observatory of Japan
The Graduate University for Advanced Studies (SOKENDAI)
National Institutes of Natural Sciences
Alexandra Muresan
Chalmers, Space, Earth and Environment, Astronomy and Plasmaphysics
Carina Persson
Chalmers, Space, Earth and Environment, Astronomy and Plasmaphysics
Vincent Van Eylen
University College London (UCL)
Astronomy and Astrophysics
0004-6361 (ISSN) 1432-0746 (eISSN)
Vol. 669 A40Exoplanets from space -CHEOPS and PLATO ESA's next two projects (Phase 2)
Swedish National Space Board (65/19), 2020-01-01 -- 2022-12-31.
Swedish National Space Board (177/19), 2020-01-01 -- 2022-12-31.
Subject Categories (SSIF 2011)
Subatomic Physics
Astronomy, Astrophysics and Cosmology
Other Physics Topics
DOI
10.1051/0004-6361/202244120