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.

Stars: individual: HD 191939

Planets and satellites: individual: HD 191939 g

Techniques: photometric

Planets and satellites: individual: HD 191939 d

Techniques: radial velocities

Author

J. Orell-Miquel

Instituto de Astrofísica de Canarias

University of La Laguna

G. Nowak

University of La Laguna

Instituto de Astrofísica de Canarias

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

University of Chicago

Institute of Astrophysics of Andalusia (IAA)

M. Badenas-Agusti

Massachusetts Institute of Technology (MIT)

I. Ribas

Institute of Space Sciences (ICE) - CSIC

Institute of Space Studies of Catalonia (IEEC)

Marina Lafarga

The University of Warwick

Néstor Espinoza

Max Planck Society

J. C. Morales

Institute of Space Sciences (ICE) - CSIC

Institute of Space Studies of Catalonia (IEEC)

M. Zechmeister

University of Göttingen

A. Alqasim

University College London (UCL)

W. D. Cochran

The University of Texas at Austin

Center for Planetary Systems Habitability

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 Institutes of Natural Sciences

National Astronomical Observatory of Japan

The Graduate University for Advanced Studies (SOKENDAI)

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 A40

Exoplanets from space -CHEOPS and PLATO ESA's next two projects (Phase 2)

Swedish National Space Board (177/19), 2020-01-01 -- 2022-12-31.

Swedish National Space Board (65/19), 2020-01-01 -- 2022-12-31.

Subject Categories

Subatomic Physics

Astronomy, Astrophysics and Cosmology

Other Physics Topics

DOI

10.1051/0004-6361/202244120

More information

Latest update

1/20/2023