Refined parameters of the HD 22946 planetary system and the true orbital period of planet d
Journal article, 2023

Context. Multi-planet systems are important sources of information regarding the evolution of planets. However, the long-period planets in these systems often escape detection. These objects in particular may retain more of their primordial characteristics compared to close-in counterparts because of their increased distance from the host star. HD 22946 is a bright (G = 8.13 mag) late F-type star around which three transiting planets were identified via Transiting Exoplanet Survey Satellite (TESS) photometry, but the true orbital period of the outermost planet d was unknown until now. Aims. We aim to use the Characterising Exoplanet Satellite (CHEOPS) space telescope to uncover the true orbital period of HD 22946d and to refine the orbital and planetary properties of the system, especially the radii of the planets. Methods. We used the available TESS photometry of HD 22946 and observed several transits of the planets b, c, and d using CHEOPS. We identified two transits of planet d in the TESS photometry, calculated the most probable period aliases based on these data, and then scheduled CHEOPS observations. The photometric data were supplemented with ESPRESSO (Echelle SPectrograph for Rocky Exoplanets and Stable Spectroscopic Observations) radial velocity data. Finally, a combined model was fitted to the entire dataset in order to obtain final planetary and system parameters. Results. Based on the combined TESS and CHEOPS observations, we successfully determined the true orbital period of the planet d to be 47.42489 ± 0.00011 days, and derived precise radii of the planets in the system, namely 1.362 ± 0.040 R, 2.328 ± 0.039 R, and 2.607 ± 0.060 R for planets b, c, and d, respectively. Due to the low number of radial velocities, we were only able to determine 3σ upper limits for these respective planet masses, which are 13.71 M, 9.72 M, and 26.57 M. We estimated that another 48 ESPRESSO radial velocities are needed to measure the predicted masses of all planets in HD 22946. We also derived stellar parameters for the host star. Conclusions. Planet c around HD 22946 appears to be a promising target for future atmospheric characterisation via transmission spectroscopy. We can also conclude that planet d, as a warm sub-Neptune, is very interesting because there are only a few similar confirmed exoplanets to date. Such objects are worth investigating in the near future, for example in terms of their composition and internal structure.

Methods: observational

Techniques: photometric

Planets and satellites: fundamental parameters

Author

Z. Garai

Eötvös Loránd University (ELTE)

Slovak Academy of Sciences

H. P. Osborn

Massachusetts Institute of Technology (MIT)

University of Bern

D. Gandolfi

University of Turin

A. Brandeker

Stockholm University

S. G. Sousa

University of Porto

M. Lendl

University of Geneva

A. Bekkelien

University of Geneva

C. Broeg

University of Bern

A. Collier Cameron

University of St Andrews

J. A. Egger

University of Bern

M.J. Hooton

University of Cambridge

University of Bern

Y. Alibert

University of Bern

L. Delrez

University of Liège

L. Fossati

Institut fur Weltraumforschung

S. Salmon

University of Geneva

T.G. Wilson

University of St Andrews

A. Bonfanti

Institut fur Weltraumforschung

A. Tuson

University of Cambridge

S. Ulmer-Moll

University of Bern

University of Geneva

L. M. Serrano

University of Turin

L. Borsato

Istituto nazionale di astrofisica (INAF)

R. Alonso

University of La Laguna

Instituto de Astrofísica de Canarias

G. Anglada

Institute of Space Sciences (ICE) - CSIC

Institute of Space Studies of Catalonia (IEEC)

J. Asquier

European Space Research and Technology Centre (ESA ESTEC)

D. Barrado

European Space Astronomy Centre (ESAC)

S.C.C. Barros

University of Porto

T. Bárczy

Admatis

W. Baumjohann

Institut fur Weltraumforschung

M. Beck

University of Geneva

T. Beck

University of Bern

W. Benz

University of Bern

N. Billot

University of Geneva

F. Biondi

Max Planck Society

Istituto nazionale di astrofisica (INAF)

X. Bonfils

Institut de Planétologie et d’Astrophysique de Grenoble (IPAG)

M. Buder

German Aerospace Center (DLR)

J. Cabrera

German Aerospace Center (DLR)

V. Cessa

University of Bern

S. Charnoz

Institut de Physique du Globe de Paris

Szilard Csizmadia

German Aerospace Center (DLR)

P. E. Cubillos

Istituto nazionale di astrofisica (INAF)

Institut fur Weltraumforschung

Melvyn B. Davies

Lund University

M. Deleuil

Laboratoire d'Astrophysique de Marseille

O. Demangeon

Institut de Planétologie et d’Astrophysique de Grenoble (IPAG)

University of Porto

B.O. Demory

University of Bern

D. Ehrenreich

University of Geneva

Anders Erikson

German Aerospace Center (DLR)

Vincent Van Eylen

University College London (UCL)

A. Fortier

University of Bern

Malcolm Fridlund

Chalmers, Space, Earth and Environment, Astronomy and Plasmaphysics

Leiden University

Michaël Gillon

University of Liège

V. Van Grootel

University of Liège

M. Gudel

University of Vienna

Maximilian N. Günther

European Space Research and Technology Centre (ESA ESTEC)

S. Hoyer

Laboratoire d'Astrophysique de Marseille

K. Isaak

European Space Research and Technology Centre (ESA ESTEC)

L. Kiss

Hungarian Academy of Sciences

M. H. Kristiansen

Brorfelde Observatory

J. Laskar

Paris Observatory

A. L. des Etangs

Institut d 'Astrophysique de Paris

C. Lovis

University of Geneva

A. Luntzer

University of Vienna

D. Magrin

Istituto nazionale di astrofisica (INAF)

P. Maxted

Keele University

C. Mordasini

University of Bern

Valerio Nascimbeni

Istituto nazionale di astrofisica (INAF)

G. Olofsson

Stockholm University

R. Ottensamer

University of Vienna

I. Pagano

Istituto nazionale di astrofisica (INAF)

E. Palle

Instituto de Astrofísica de Canarias

University of La Laguna

G. Peter

German Aerospace Center (DLR)

Giampaolo P. Piotto

University of Padua

Istituto nazionale di astrofisica (INAF)

Don L. Pollacco

The University of Warwick

D. Queloz

University of Geneva

University of Cambridge

Roberto Ragazzoni

University of Padua

Istituto nazionale di astrofisica (INAF)

N. Rando

European Space Research and Technology Centre (ESA ESTEC)

H. Rauer

German Aerospace Center (DLR)

Technische Universität Berlin

I. Ribas

Institute of Space Sciences (ICE) - CSIC

Institute of Space Studies of Catalonia (IEEC)

N. C. Santos

University of Porto

Gaetano Scandariato

Istituto nazionale di astrofisica (INAF)

D. Segransan

University of Geneva

A.E. Simon

University of Bern

A. M.S. Smith

German Aerospace Center (DLR)

Manfred B. Steller

Institut fur Weltraumforschung

G.M. Szabó

Eötvös Loránd University (ELTE)

Nicolas Thomas

University of Bern

S. Udry

University of Geneva

J. Venturini

University of Geneva

N. A. Walton

University of Cambridge

Astronomy and Astrophysics

0004-6361 (ISSN) 1432-0746 (eISSN)

Vol. 674 A44

Exoplanet diversity with satellite studies

Swedish National Space Board (174/18), 2019-02-04 -- 2023-08-01.

Subject Categories

Astronomy, Astrophysics and Cosmology

DOI

10.1051/0004-6361/202345943

More information

Latest update

9/15/2023