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CHEOPS observations confirm nodal precession in the WASP-33 system

Smith, A.M.S. ; Davies, M.B. LU ; Korth, J. LU and Wolf, S. (2025) In Astronomy and Astrophysics 693.
Abstract
Aims. We aim to observe the transits and occultations of WASP-33 b, which orbits a rapidly rotating δ Scuti pulsator, with the goal of measuring the orbital obliquity via the gravity-darkening effect, and constraining the geometric albedo via the occultation depth. Methods. We observed four transits and four occultations with CHEOPS, and employ a variety of techniques to remove the effects of the stellar pulsations from the light curves, as well as the usual CHEOPS systematic effects. We also performed a comprehensive analysis of low-resolution spectral and Gaia data to re-determine the stellar properties of WASP-33. Results. We measure an orbital obliquity 111.3+−00.27 degrees, which is consistent with previous measurements made via... (More)
Aims. We aim to observe the transits and occultations of WASP-33 b, which orbits a rapidly rotating δ Scuti pulsator, with the goal of measuring the orbital obliquity via the gravity-darkening effect, and constraining the geometric albedo via the occultation depth. Methods. We observed four transits and four occultations with CHEOPS, and employ a variety of techniques to remove the effects of the stellar pulsations from the light curves, as well as the usual CHEOPS systematic effects. We also performed a comprehensive analysis of low-resolution spectral and Gaia data to re-determine the stellar properties of WASP-33. Results. We measure an orbital obliquity 111.3+−00.27 degrees, which is consistent with previous measurements made via Doppler tomography. We also measure the planetary impact parameter, and confirm that this parameter is undergoing rapid secular evolution as a result of nodal precession of the planetary orbit. This precession allows us to determine the second-order fluid Love number of the star, which we find agrees well with the predictions of theoretical stellar models. We are unable to robustly measure a unique value of the occultation depth, and emphasise the need for long-baseline observations to better measure the pulsation periods. © The Authors 2025. (Less)
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published
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keywords
planets and satellites: dynamical evolution and stability, planets and satellites: fundamental parameters, planets and satellites: gaseous planets, planets and satellites: individual: WASP-33 b, stars: individual: WASP-33, stars: oscillations, Orbits, Stars, Orbitals, Planet and satellite: gaseous planet, Planet and satellite: individual: WASP-33 b, Planets and satellites, Planets and satellites: dynamical evolution and stabilities, Planets and satellites: fundamental parameters, Planets and satellites: individual, Star oscillations, Star: individual: WASP-33, Stars: individual: proxima Centauri, Planets
in
Astronomy and Astrophysics
volume
693
article number
A128
publisher
EDP Sciences
external identifiers
  • scopus:85215419388
ISSN
0004-6361
DOI
10.1051/0004-6361/202452151
language
English
LU publication?
yes
id
8613fcf5-f628-4df4-8823-fa04a13cea7c
date added to LUP
2025-12-17 09:33:10
date last changed
2025-12-17 09:33:37
@article{8613fcf5-f628-4df4-8823-fa04a13cea7c,
  abstract     = {{Aims. We aim to observe the transits and occultations of WASP-33 b, which orbits a rapidly rotating δ Scuti pulsator, with the goal of measuring the orbital obliquity via the gravity-darkening effect, and constraining the geometric albedo via the occultation depth. Methods. We observed four transits and four occultations with CHEOPS, and employ a variety of techniques to remove the effects of the stellar pulsations from the light curves, as well as the usual CHEOPS systematic effects. We also performed a comprehensive analysis of low-resolution spectral and Gaia data to re-determine the stellar properties of WASP-33. Results. We measure an orbital obliquity 111.3+−00.27 degrees, which is consistent with previous measurements made via Doppler tomography. We also measure the planetary impact parameter, and confirm that this parameter is undergoing rapid secular evolution as a result of nodal precession of the planetary orbit. This precession allows us to determine the second-order fluid Love number of the star, which we find agrees well with the predictions of theoretical stellar models. We are unable to robustly measure a unique value of the occultation depth, and emphasise the need for long-baseline observations to better measure the pulsation periods. © The Authors 2025.}},
  author       = {{Smith, A.M.S. and Davies, M.B. and Korth, J. and Wolf, S.}},
  issn         = {{0004-6361}},
  keywords     = {{planets and satellites: dynamical evolution and stability; planets and satellites: fundamental parameters; planets and satellites: gaseous planets; planets and satellites: individual: WASP-33 b; stars: individual: WASP-33; stars: oscillations; Orbits; Stars; Orbitals; Planet and satellite: gaseous planet; Planet and satellite: individual: WASP-33 b; Planets and satellites; Planets and satellites: dynamical evolution and stabilities; Planets and satellites: fundamental parameters; Planets and satellites: individual; Star oscillations; Star: individual: WASP-33; Stars: individual: proxima Centauri; Planets}},
  language     = {{eng}},
  publisher    = {{EDP Sciences}},
  series       = {{Astronomy and Astrophysics}},
  title        = {{CHEOPS observations confirm nodal precession in the WASP-33 system}},
  url          = {{http://dx.doi.org/10.1051/0004-6361/202452151}},
  doi          = {{10.1051/0004-6361/202452151}},
  volume       = {{693}},
  year         = {{2025}},
}