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
Planets and satellites: fundamental parameters
Techniques: photometric
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 Bern
University of Cambridge
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 Geneva
University of Bern
L. M. Serrano
University of Turin
L. Borsato
Istituto nazionale di astrofisica (INAF)
R. Alonso
Instituto de Astrofísica de Canarias
University of La Laguna
G. Anglada
Spanish National Research Council (CSIC)
Centre Tecnològic de Telecomunicacions de Catalunya (CTTC)
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
Istituto nazionale di astrofisica (INAF)
Max Planck Society
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
Institut fur Weltraumforschung
Istituto nazionale di astrofisica (INAF)
Melvyn B. Davies
Lund University
M. Deleuil
Laboratoire d'Astrophysique de Marseille
O. Demangeon
University of Porto
Institut de Planétologie et d’Astrophysique de Grenoble (IPAG)
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
Leiden University
Chalmers, Space, Earth and Environment, Astronomy and Plasmaphysics
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
Istituto nazionale di astrofisica (INAF)
University of Padua
Don L. Pollacco
The University of Warwick
D. Queloz
University of Geneva
University of Cambridge
Roberto Ragazzoni
Istituto nazionale di astrofisica (INAF)
University of Padua
N. Rando
European Space Research and Technology Centre (ESA ESTEC)
H. Rauer
Technische Universität Berlin
German Aerospace Center (DLR)
I. Ribas
Spanish National Research Council (CSIC)
Centre Tecnològic de Telecomunicacions de Catalunya (CTTC)
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 A44Exoplanet diversity with satellite studies
Swedish National Space Board (174/18), 2019-02-04 -- 2023-08-01.
Subject Categories (SSIF 2011)
Astronomy, Astrophysics and Cosmology
DOI
10.1051/0004-6361/202345943