CHEOPS observations confirm nodal precession in the WASP-33 system
Abstract
Aims: We aim to observe the transits and occultations of WASP-33b, which orbits a rapidly-rotating 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 +0.2 -0.7 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.
Cite
@article{arxiv.2412.08557,
title = {CHEOPS observations confirm nodal precession in the WASP-33 system},
author = {A. M. S. Smith and Sz. Csizmadia and V. Van Grootel and M. Lendl and C. M. Persson and G. Olofsson and D. Ehrenreich and M. N. Günther and A. Heitzmann and S. C. C. Barros and A. Bonfanti and A. Brandeker and J. Cabrera and O. D. S. Demangeon and L. Fossati and J. -V. Harre and M. J. Hooton and S. Hoyer and Sz. Kalman and S. Salmon and S. G. Sousa and Gy. M. Szabó and T. G. Wilson and Y. Alibert and R. Alonso and J. Asquier and T. Bárczy and D. Barrado and W. Baumjohann and W. Benz and N. Billot and L. Borsato and C. Broeg and A. Collier Cameron and A. C. M. Correia and P. E. Cubillos and M. B. Davies and M. Deleuil and A. Deline and B. -O. Demory and A. Derekas and B. Edwards and J. A. Egger and A. Erikson and A. Fortier and M. Fridlund and D. Gandolfi and K. Gazeas and M. Gillon and M. Güdel and J. Hasiba and Ch. Helling and K. G. Isaak and L. L. Kiss and J. Korth and K. W. F. Lam and J. Laskar and A. Lecavelier des Etangs and D. Magrin and P. F. L. Maxted and B. Merín and C. Mordasini and V. Nascimbeni and R. Ottensamer and I. Pagano and E. Pallé and G. Peter and D. Piazza and G. Piotto and D. Pollacco and D. Queloz and R. Ragazzoni and N. Rando and H. Rauer and I. Ribas and N. C. Santos and G. Scandariato and D. Ségransan and A. E. Simon and M. Stalport and S. Sulis and S. Udry and S. Ulmer-Moll and J. Venturini and E. Villaver and V. Viotto and I. Walter and N. A. Walton and S. Wolf},
journal= {arXiv preprint arXiv:2412.08557},
year = {2025}
}
Comments
18 pages, 12 figures. Accepted for publication in Astronomy & Astrophysics