Transit timing variations in HIP 41378: CHEOPS and TESS confirm a non-transiting sixth planet in the system
Journal article, 2025
In multiple-planet systems, gravitational interactions of exoplanets could lead to transit timing variations (TTVs), whose amplitude becomes significantly enhanced when planets are in or near mean-motion resonances (MMRs), making them more easily detectable. In cases where both TTVs and radial velocity (RV) measurements are available, combined analysis can break degeneracies and provide robust planetary and system characterization, even detecting non-transiting planets. In this context, HIP 41378 hosts five confirmed transiting planets with periods ranging from 15 to over 542 days, providing a unique dynamical laboratory for investigating wide multi-planet systems analogous to the Solar System. In this study, we present an intensive space-based photometric follow-up of HIP 41378, combining 15 new CHEOPS observations with eight TESS sectors, alongside data from K2, Spitzer, HST, and 311 HARPS spectra. We dynamically modeled the TTVs and RV signals of the two inner sub-Neptunes via N-body integration. These planets, HIP 41378 b (Pb = 15.57 days, Rb = 2.45 R⊕) and HIP 41378 c (Pc = 31.71 days, Rc = 2.57 R⊕), are close to (Δ ~ 1.8%) a 2:1 period commensurability. We report a clear detection of TTVs with amplitudes of 20 minutes for planet b and greater than 3 hours for planet c. We dynamically confirm the planetary nature of HIP 41378 g, a non-transiting planet with a period of about 64 days and a mass of about 7 M⊕, close to a 2:1 commensurability with planet c, suggesting a possible mean-motion resonance chain in the inner system. Our precise determination of the masses, eccentricities, and radii of HIP 41378 b and c enabled us to investigate their possible volatile-rich compositions. Finally, by leveraging on the last TESS sectors we constrained the period of HIP 41378 d to three possible aliases (Pd = 278, 371, and 1113 days) suggesting that the system could be placed in a double quasi resonant chain, highlighting its complex dynamical architecture.
planets and satellites: dynamical evolution and stability
methods: data analysis
techniques: photometric
planets and satellites: detection
stars: individual: HIP 41378
Author
P. Leonardi
University of Trento
Istituto nazionale di astrofisica (INAF)
University of Padua
Institut fur Weltraumforschung
L. Borsato
Istituto nazionale di astrofisica (INAF)
L. Pagliaro
University of Padua
D. Kubyshkina
Institut fur Weltraumforschung
J. A. Egger
University of Bern
T.G. Wilson
The University of Warwick
A. Heitzmann
University of Geneva
A. Brandeker
Stockholm University
Maximilian N. Günther
European Space Agency (ESA)
Valerio Nascimbeni
Istituto nazionale di astrofisica (INAF)
A. Leleu
University of Geneva
University of Bern
A. Bonfanti
Institut fur Weltraumforschung
S.G. Sousa
University of Porto
G. Mantovan
University of Padua
Giampaolo P. Piotto
University of Padua
Istituto nazionale di astrofisica (INAF)
L. Fossati
Institut fur Weltraumforschung
D. Nardiello
University of Padua
Tiziano Zingales
University of Padua
Istituto nazionale di astrofisica (INAF)
V. Adibekyan
University of Porto
C. Pezzotti
University of Liège
B. Akinsanmi
University of Geneva
Y. Alibert
University of Bern
R. Alonso
University of La Laguna
Instituto de Astrofísica de Canarias
T. Bárczy
Admatis
D. Barrado
European Space Agency (ESA)
S.C.C. Barros
University of Porto
W. Baumjohann
Institut fur Weltraumforschung
W. Benz
University of Bern
N. Billot
University of Geneva
C. Broeg
University of Bern
M. Buder
German Aerospace Center (DLR)
A. Collier Cameron
University of St Andrews
C. Corral Van Damme
European Space Agency (ESA)
A. Correia
University of Coimbra
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
A. Deline
University of Geneva
O. Demangeon
University of Porto
B.O. Demory
University of Bern
A. Derekas
Eötvös Loránd University (ELTE)
Billy Edwards
Netherlands Institute for Space Research (SRON)
D. Ehrenreich
University of Geneva
Anders Erikson
German Aerospace Center (DLR)
J. Farinato
Istituto nazionale di astrofisica (INAF)
A. Fortier
University of Bern
Malcolm Fridlund
Chalmers, Space, Earth and Environment, Astronomy and Plasmaphysics
Leiden University
D. Gandolfi
University of Turin
K. Gazeas
University of Athens
Michaël Gillon
University of Liège
M. Gudel
University of Vienna
Ch. Helling
Institut fur Weltraumforschung
Technische Universität Graz
K. Isaak
European Space Agency (ESA)
L. L. Kiss
Eötvös Loránd University (ELTE)
Hungarian Academy of Sciences
Judith Korth
Lund University
K. W.F. Lam
German Aerospace Center (DLR)
J. Laskar
Paris Observatory
A. L. des Etangs
Institut d 'Astrophysique de Paris
M. Lendl
University of Geneva
D. Magrin
Istituto nazionale di astrofisica (INAF)
P. Maxted
Keele University
Bruno Merín
European Space Agency (ESA)
C. Mordasini
University of Bern
G. Olofsson
Stockholm University
R. Ottensamer
University of Vienna
I. Pagano
Istituto nazionale di astrofisica (INAF)
Enric Palle
University of La Laguna
Instituto de Astrofísica de Canarias
G. Peter
German Aerospace Center (DLR)
D. Piazza
University of Bern
Don L. Pollacco
The University of Warwick
D. Queloz
University of Cambridge
Swiss Federal Institute of Technology in Zürich (ETH)
Roberto Ragazzoni
Istituto nazionale di astrofisica (INAF)
University of Padua
N. Rando
European Space Agency (ESA)
H. Rauer
Freie Universität Berlin
German Aerospace Center (DLR)
I. Ribas
Centre Tecnològic de Telecomunicacions de Catalunya (CTTC)
Spanish National Research Council (CSIC)
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)
M. Stalport
University of Liège
S. Sulis
Laboratoire d'Astrophysique de Marseille
G.M. Szabó
Eötvös Loránd University (ELTE)
S. Udry
University of Geneva
B. Ulmer
German Aerospace Center (DLR)
S. Ulmer-Moll
University of Cambridge
University of Liège
V. Van Grootel
University of Liège
J. Venturini
University of Geneva
E. Villaver
University of La Laguna
Instituto de Astrofísica de Canarias
N. A. Walton
University of Cambridge
S. Wolf
University of Bern
Astronomy and Astrophysics
0004-6361 (ISSN) 1432-0746 (eISSN)
Vol. 702 A211Subject Categories (SSIF 2025)
Astronomy, Astrophysics, and Cosmology
DOI
10.1051/0004-6361/202555253