CHEOPS observations confirm nodal precession in the WASP-33 system

• Published in: arXiv.org 2024-12
• Main Authors: Smith, A M S, Csizmadia, Sz, V Van Grootel, Lendl, M, Persson, C M, Olofsson, G, Ehrenreich, D, Günther, M N, Heitzmann, A, Barros, S C C, Bonfanti, A, Brandeker, A, Cabrera, J, Demangeon, O D S, Fossati, L, J -V Harre, Hooton, M J, Hoyer, S, Kalman, Sz, Salmon, S, Sousa, S G, Szabó, Gy M, Wilson, T G, Alibert, Y, Alonso, R, Asquier, J, Bárczy, T, Barrado, D, Baumjohann, W, Benz, W, Billot, N, Borsato, L, Broeg, C, A Collier Cameron, Correia, A C M, Cubillos, P E, Davies, M B, Deleuil, M, Deline, A, B -O Demory, Derekas, A, Edwards, B, Egger, J A, Erikson, A, tier, A, Fridlund, M, Gandolfi, D, Gazeas, K, Gillon, M, Güdel, M, Hasiba, J, Helling, Ch, Isaak, K G, Kiss, L L, Korth, J, Lam, K W F, Laskar, J, A Lecavelier des Etangs, Magrin, D, Maxted, P F L, Merín, B, Mordasini, C, Nascimbeni, V, Ottensamer, R, Pagano, I, Pallé, E, Peter, G, Piazza, D, Piotto, G, Pollacco, D, Queloz, D, Ragazzoni, R, Rando, N, Rauer, H, Ribas, I, Santos, N C, Scandariato, G, Ségransan, D, Simon, A E, Stalport, M, Sulis, S, Udry, S, Ulmer-Moll, S, Venturini, J, Villaver, E, Viotto, V, Walter, I, Walton, N A, Wolf, S
• Format: Article
• Language: English
• Subjects: Astronomical models; Light curve; Love number; Parameters; Planetary evolution; Planetary orbits; Precession; Stellar models
• ISSN: 2331-8422

Aims: We aim to observe the transits and occultations of WASP-33b, which orbits a rapidly-rotating \(\delta\) 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.