Issue |
A&A
Volume 685, May 2024
|
|
---|---|---|
Article Number | A63 | |
Number of page(s) | 24 | |
Section | Interstellar and circumstellar matter | |
DOI | https://doi.org/10.1051/0004-6361/202348502 | |
Published online | 08 May 2024 |
The tidal deformation and atmosphere of WASP-12 b from its phase curve★,★★
1
Observatoire astronomique de l’Université de Genève,
Chemin Pegasi 51,
1290
Versoix,
Switzerland
e-mail: tunde.akinsanmi@unige.ch
2
Instituto de Astrofisica e Ciencias do Espaco, Universidade do Porto, CAUP,
Rua das Estrelas,
4150-762
Porto,
Portugal
3
Departamento de Fisica e Astronomia, Faculdade de Ciencias, Universidade do Porto,
Rua do Campo Alegre,
4169-007
Porto,
Portugal
4
Space Research Institute, Austrian Academy of Sciences,
Schmiedl-strasse 6,
8042
Graz,
Austria
5
INAF, Osservatorio Astrofisico di Torino,
Via Osservatorio, 20,
10025
Pino Torinese To,
Italy
6
Weltraumforschung und Planetologie, Physikalisches Institut, University of Bern,
Gesellschaftsstrasse 6,
3012
Bern,
Switzerland
7
Center for Space and Habitability, University of Bern,
Gesellschaftsstrasse 6,
3012
Bern,
Switzerland
8
Department of Astronomy, Stockholm University,
AlbaNova University Center,
10691
Stockholm,
Sweden
9
Centre for Exoplanet Science, SUPA School of Physics and Astronomy, University of St Andrews,
North Haugh,
St Andrews
KY16 9SS,
UK
10
IMCCE, UMR8028 CNRS, Observatoire de Paris, PSL Univ., Sorbonne Univ.,
77 av. Denfert-Rochereau,
75014
Paris,
France
11
INAF, Osservatorio Astrofisico di Catania,
Via S. Sofia 78,
95123
Catania,
Italy
12
Department of Physics, University of Warwick,
Gibbet Hill Road,
Coventry
CV4 7AL,
UK
13
Cavendish Laboratory,
JJ Thomson Avenue,
Cambridge
CB3 0HE,
UK
14
Institute of Planetary Research, German Aerospace Center (DLR),
Rutherfordstrasse 2,
12489
Berlin,
Germany
15
Instituto de Astrofisica de Canarias,
Via Lactea s/n,
38200
La Laguna,
Tenerife,
Spain
16
Departamento de Astrofisica, Universidad de La Laguna,
Astrofísico Francisco Sanchez s/n,
38206 La
Laguna,
Tenerife,
Spain
17
European Space Agency (ESA), ESTEC,
Keplerlaan 1,
2201 AZ
Noordwijk,
The Netherlands
18
Admatis,
5. Kandó Kálmán Street,
3534
Miskolc,
Hungary
19
Depto. de Astrofisica, Centro de Astrobiologia (CSIC-INTA),
ESAC campus,
28692
Villanueva de la Cañada (Madrid),
Spain
20
Université Grenoble Alpes, CNRS, IPAG,
38000
Grenoble,
France
21
INAF, Osservatorio Astronomico di Padova,
Vicolo dell’Osservatorio 5,
35122
Padova,
Italy
22
Institute of Optical Sensor Systems, German Aerospace Center (DLR),
Rutherfordstrasse 2,
12489
Berlin,
Germany
23
Université de Paris Cité, Institut de physique du globe de Paris, CNRS,
1 Rue Jussieu,
75005
Paris,
France
24
Centre for Mathematical Sciences, Lund University,
Box 118,
221 00
Lund,
Sweden
25
Aix Marseille Univ, CNRS, CNES, LAM,
38 rue Frédéric Joliot-Curie,
13388
Marseille,
France
26
Astrobiology Research Unit, Université de Liège,
Allée du 6 Août 19C,
4000
Liège,
Belgium
27
Space sciences, Technologies and Astrophysics Research (STAR) Institute, Université de Liège,
Allée du 6 Août 19C,
4000
Liège,
Belgium
28
Centre Vie dans l’Univers, Faculté des sciences, Université de Genève,
Quai Ernest-Ansermet 30,
1211
Genève 4,
Switzerland
29
Leiden Observatory, University of Leiden,
PO Box 9513,
2300 RA
Leiden,
The Netherlands
30
Department of Space, Earth and Environment, Chalmers University of Technology,
Onsala Space Observatory,
439 92
Onsala,
Sweden
31
Dipartimento di Fisica, Università degli Studi di Torino,
via Pietro Giuria 1,
10125
Torino,
Italy
32
Department of Astrophysics, University of Vienna,
Türkenschanzs-trasse 17,
1180
Vienna,
Austria
33
Institute for Theoretical Physics and Computational Physics, Graz University of Technology,
Petersgasse 16,
8010
Graz,
Austria
34
Konkoly Observatory, Research Centre for Astronomy and Earth Sciences,
1121 Budapest,
Konkoly Thege Miklós
út 15–17,
Hungary
35
ELTE Eötvös Loránd University, Institute of Physics,
Pázmány Péter sétány 1/A,
1117
Budapest,
Hungary
36
Institut d’astrophysique de Paris, UMR7095 CNRS, Université Pierre & Marie Curie,
98bis blvd. Arago,
75014
Paris,
France
37
Astrophysics Group, Lennard Jones Building, Keele University,
Staffordshire
ST5 5BG,
UK
38
Physikalisches Institut, University of Bern,
Gesellschaftsstrasse 6,
3012
Bern,
Switzerland
39
Dipartimento di Fisica e Astronomia “Galileo Galilei”, Università degli Studi di Padova,
Vicolo dell’Osservatorio 3,
35122
Padova,
Italy
40
ETH Zurich, Department of Physics,
Wolfgang-Pauli-Strasse 2,
8093
Zurich,
Switzerland
41
Zentrum für Astronomie und Astrophysik, Technische Universität Berlin,
Hardenbergstr. 36,
10623
Berlin,
Germany
42
Institut fuer Geologische Wissenschaften, Freie Universitaet Berlin,
Maltheserstrasse 74-100,
12249
Berlin,
Germany
43
Institut de Ciencies de l’Espai (ICE, CSIC), Campus UAB,
Can Magrans s/n,
08193
Bellaterra,
Spain
44
Institut d’Estudis Espacials de Catalunya (IEEC),
Gran Capità 2–4,
08034
Barcelona,
Spain
45
ELTE Eötvös Loránd University, Gothard Astrophysical Observatory,
9700
Szombathely,
SzentImre h. u. 112,
Hungary
46
HUN-REN-ELTE Exoplanet Research Group,
Szent Imre h. u. 112,
Szombathely,
9700,
Hungary
47
Institute of Astronomy, University of Cambridge,
Madingley Road,
Cambridge
CB3 0HA,
UK
48
CFisUC, Departamento de Fisica, Universidade de Coimbra,
3004516
Coimbra,
Portugal
Received:
6
November
2023
Accepted:
5
February
2024
Context. Ultra-hot Jupiters present a unique opportunity to understand the physics and chemistry of planets, their atmospheres, and interiors at extreme conditions. WASP-12 b stands out as an archetype of this class of exoplanets, with a close-in orbit around its star that results in intense stellar irradiation and tidal effects.
Aims. The goals are to measure the planet’s tidal deformation, atmospheric properties, and also to refine its orbital decay rate.
Methods. We performed comprehensive analyses of the transits, occultations, and phase curves of WASP-12b by combining new CHEOPS observations with previous TESS and Spitzer data. The planet was modeled as a triaxial ellipsoid parameterized by the second-order fluid Love number of the planet, h2, which quantifies its radial deformation and provides insight into the interior structure.
Results. We measured the tidal deformation of WASP-12b and estimated a Love number of h2 = 1.55−0.49+0.45 (at 3.2σ) from its phase curve. We measured occultation depths of 333 ± 24 ppm and 493 ± 29 ppm in the CHEOPS and TESS bands, respectively, while the nightside fluxes are consistent with zero, and also marginal eastward phase offsets. Our modeling of the dayside emission spectrum indicates that CHEOPS and TESS probe similar pressure levels in the atmosphere at a temperature of ~2900 K. We also estimated low geometric albedos of Ag = 0.086 ± 0.017 and Ag = 0.01 ± 0.023 in the CHEOPS and TESS passbands, respectively, suggesting the absence of reflective clouds in the high-temperature dayside of the planet. The CHEOPS occultations do not show strong evidence for variability in the dayside atmosphere of the planet at the median occultation depth precision of 120 ppm attained. Finally, combining the new CHEOPS timings with previous measurements refines the precision of the orbital decay rate by 12% to a value of −30.23 ± 0.82 ms yr−1, resulting in a modified stellar tidal quality factor of Q′★ = 1.70 ± 0.14 × 105.
Conclusions. WASP-12 b becomes the second exoplanet, after WASP-103b, for which the Love number has been measured from the effect of tidal deformation in the light curve. However, constraining the core mass fraction of the planet requires measuring h2 with a higher precision. This can be achieved with high signal-to-noise observations with JWST since the phase curve amplitude, and consequently the induced tidal deformation effect, is higher in the infrared.
Key words: planets and satellites: individual: WASP-12b / planets and satellites: interiors
The CHEOPS photometric time-series data used in this paper are available at the CDS via anonymous ftp to cdsarc.cds.unistra.fr (130.79.128.5) or via https://cdsarc.cds.unistra.fr/viz-bin/cat/J/A+A/685/A63
© The Authors 2024
Open Access article, published by EDP Sciences, under the terms of the Creative Commons Attribution License (https://creativecommons.org/licenses/by/4.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.
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