Detection of the tidal deformation of WASP-103b at 3 σ with CHEOPS
Journal article, 2022
Context. Ultra-short period planets undergo strong tidal interactions with their host star which lead to planet deformation and orbital tidal decay. Aims. WASP-103b is the exoplanet with the highest expected deformation signature in its transit light curve and one of the shortest expected spiral-in times. Measuring the tidal deformation of the planet would allow us to estimate the second degree fluid Love number and gain insight into the planet's internal structure. Moreover, measuring the tidal decay timescale would allow us to estimate the stellar tidal quality factor, which is key to constraining stellar physics. Methods. We obtained 12 transit light curves of WASP-103b with the CHaracterising ExOplanet Satellite (CHEOPS) to estimate the tidal deformation and tidal decay of this extreme system. We modelled the high-precision CHEOPS transit light curves together with systematic instrumental noise using multi-dimensional Gaussian process regression informed by a set of instrumental parameters. To model the tidal deformation, we used a parametrisation model which allowed us to determine the second degree fluid Love number of the planet. We combined our light curves with previously observed transits of WASP-103b with the Hubble Space Telescope (HST) and Spitzer to increase the signal-to-noise of the light curve and better distinguish the minute signal expected from the planetary deformation. Results. We estimate the radial Love number of WASP-103b to be hf = 1.59-0.53+0.45. This is the first time that the tidal deformation is directly detected (at 3 σ) from the transit light curve of an exoplanet. Combining the transit times derived from CHEOPS, HST, and Spitzer light curves with the other transit times available in the literature, we find no significant orbital period variation for WASP-103b. However, the data show a hint of an orbital period increase instead of a decrease, as is expected for tidal decay. This could be either due to a visual companion star if this star is bound, the Applegate effect, or a statistical artefact. Conclusions. The estimated Love number of WASP-103b is similar to Jupiter's. This will allow us to constrain the internal structure and composition of WASP-103b, which could provide clues on the inflation of hot Jupiters. Future observations with James Webb Space Telescope can better constrain the radial Love number of WASP-103b due to their high signal-to-noise and the smaller signature of limb darkening in the infrared. A longer time baseline is needed to constrain the tidal decay in this system.
Planets and satellites: interiors
Planets and satellites: composition
Planets and satellites: fundamental parameters
Time
Techniques: photometric
Planets and satellites: individual: WASP-103b
Author
S. C.C. Barros
University of Porto
B. Akinsanmi
University of Porto
University of Geneva
G. Boue´
Paris Observatory
A. M.S. Smith
German Aerospace Center (DLR)
J. Laskar
Paris Observatory
S. Ulmer-Moll
University of Geneva
J. Lillo-Box
Centro de Astrobiologia (CAB)
D. Queloz
University of Cambridge
University of Geneva
A. Collier Cameron
University of St Andrews
S. G. Sousa
University of Porto
D. Ehrenreich
University of Geneva
M.J. Hooton
University of Bern
G. Bruno
Istituto nazionale di astrofisica (INAF)
B.O. Demory
University of Bern
A. C.M. Correia
University of Coimbra
O. Demangeon
University of Porto
T.G. Wilson
University of St Andrews
A. Bonfanti
Institut fur Weltraumforschung
S. Hoyer
Aix Marseille University
Y. Alibert
University of Bern
R. Alonso
Instituto de Astrofísica de Canarias
University of La Laguna
G. A. Escudé
Centre Tecnològic de Telecomunicacions de Catalunya (CTTC)
Spanish National Research Council (CSIC)
D. Barbato
University of Geneva
T. Bárczy
Admatis
D. Barrado
Centro de Astrobiologia (CAB)
W. Baumjohann
Institut fur Weltraumforschung
M. Beck
University of Geneva
T. Beck
University of Bern
W. Benz
University of Bern
M. Bergomi
Istituto nazionale di astrofisica (INAF)
N. Billot
University of Geneva
X. Bonfils
Grenoble Alpes University
F. Bouchy
University of Geneva
A. Brandeker
Stockholm University
C. Broeg
University of Bern
J. Cabrera
German Aerospace Center (DLR)
V. Cessa
University of Bern
S. Charnoz
Paris Descartes University
C. C.V. Damme
European Space Agency (ESA)
M. B. Davies
Lund University
M. Deleuil
Aix Marseille University
A. Deline
University of Geneva
L. Delrez
University of Liège
Anders Erikson
German Aerospace Center (DLR)
A. Fortier
University of Bern
L. Fossati
Institut fur Weltraumforschung
Malcolm Fridlund
Chalmers, Space, Earth and Environment, Astronomy and Plasmaphysics
Leiden University
D. Gandolfi
University of Turin
A. Garciá Muñoz
Technische Universität Berlin
Michaël Gillon
University of Liège
M. Gudel
University of Vienna
K. Isaak
European Space Agency (ESA)
Kevin Heng
University of Bern
The University of Warwick
L.L. Kiss
The University of Sydney
Hungarian Academy of Sciences
A. L. des Etangs
Institut d 'Astrophysique de Paris
M. Lendl
University of Geneva
C. Lovis
University of Geneva
D. Magrin
Istituto nazionale di astrofisica (INAF)
Valerio Nascimbeni
Istituto nazionale di astrofisica (INAF)
P. Maxted
Keele University
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
H. Parviainen
University of La Laguna
Instituto de Astrofísica de Canarias
G. Peter
German Aerospace Center (DLR)
Giampaolo P. Piotto
University of Padua
Istituto nazionale di astrofisica (INAF)
Don L. Pollacco
The University of Warwick
Roberto Ragazzoni
Istituto nazionale di astrofisica (INAF)
University of Padua
N. Rando
European Space Agency (ESA)
H. Rauer
German Aerospace Center (DLR)
Freie Universität Berlin
Technische Universität Berlin
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
Manfred B. Steller
Institut fur Weltraumforschung
Gy M. Szabó
Eötvös Loránd University (ELTE)
Nicolas Thomas
University of Bern
S. Udry
University of Geneva
B. Ulmer
Ingenieurbüro Ulmer - Technische Informatik
V. Van Grootel
University of Liège
N. A. Walton
University of Cambridge
Astronomy and Astrophysics
0004-6361 (ISSN) 1432-0746 (eISSN)
Vol. 657 A52Subject Categories (SSIF 2011)
Astronomy, Astrophysics and Cosmology
DOI
10.1051/0004-6361/202142196