CHEOPS observations confirm nodal precession in the WASP-33 system
Creators: name: Smith, A. M. S.
name: Csizmadia, Sz.
name: Van Grootel, V.
name: Lendl, M.
name: Persson, C. M.
name: Olofsson, G.
name: Ehrenreich, D.
name: Günther, M. N.
name: Heitzmann, A.
name: Barros, S. C. C.
name: Bonfanti, A.
name: Brandeker, A.
name: Cabrera, J.
name: Demangeon, O. D. S.
name: Fossati, L.
name: Harre, J. -V.
name: Hooton, M. J.
name: Hoyer, S.
name: Kalman, Sz.
name: Salmon, S.
name: Sousa, S. G.
name: Szabó, Gy. M.
name: Wilson, T. G.
name: Alibert, Y.
name: Alonso, R.
name: Asquier, J.
name: Bárczy, T.
name: Barrado, D.
name: Baumjohann, W.
name: Benz, W.
name: Billot, N.
name: Borsato, L.
name: Broeg, C.
name: Cameron, A. Collier
name: Correia, A. C. M.
name: Cubillos, P. E.
name: Davies, M. B.
name: Deleuil, M.
name: Deline, A.
name: Demory, B. -O.
name: Derekas, A.
name: Edwards, B.
name: Egger, J. A.
name: Erikson, A.
name: Fortier, A.
name: Fridlund, M.
name: Gandolfi, D.
name: Gazeas, K.
name: Gillon, M.
name: Güdel, M.
name: Hasiba, J.
name: Helling, Ch.
name: Isaak, K. G.
name: Kiss, L. L.
name: Korth, J.
name: Lam, K. W. F.
name: Laskar, J.
name: Etangs, A. Lecavelier des
name: Magrin, D.
name: Maxted, P. F. L.
name: Merín, B.
name: Mordasini, C.
name: Nascimbeni, V.
name: Ottensamer, R.
name: Pagano, I.
name: Pallé, E.
name: Peter, G.
name: Piazza, D.
name: Piotto, G.
name: Pollacco, D.
name: Queloz, D.
name: Ragazzoni, R.
name: Rando, N.
name: Rauer, H.
name: Ribas, I.
name: Santos, N. C.
name: Scandariato, G.
name: Ségransan, D.
name: Simon, A. E.
name: Stalport, M.
name: Sulis, S.
name: Udry, S.
name: Ulmer-Moll, S.
name: Venturini, J.
name: Villaver, E.
name: Viotto, V.
name: Walter, I.
name: Walton, N. A.
name: Wolf, S.
Publisher: name: arXiv
Year: 2024
Subjects: subject: Earth and Planetary Astrophysics (astro-ph.EP)
subject: Solar and Stellar Astrophysics (astro-ph.SR)
subject: FOS: Physical sciences
subject: FOS: Physical sciences

description: Aims: We aim to observe the transits and occultations of WASP-33b, 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 +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.
description: 18 pages, 12 figures. Accepted for publication in Astronomy &amp; Astrophysics