The atmosphere and architecture of WASP-189 b probed by its CHEOPS phase curve

Author(s): A. Deline, M. J. Hooton, M. Lendl, B. Morris, S. Salmon, G. Olofsson, C. Broeg, D. Ehrenreich, M. Beck, A. Brandeker, S. Hoyer, S. Sulis, V. Van Grootel, V. Bourrier, O. Demangeon, B. O. Demory, K. Heng, H. Parviainen, L. M. Serrano, V. Singh, A. Bonfanti, L. Fossati, D. Kitzmann, S. G. Sousa, T. G. Wilson, Y. Alibert, Roi Alonso, G. Anglada, T. Bárczy, D. Barrado Navascues, S. C.C. Barros, W. Baumjohann, T. Beck, A. Bekkelien, W. Benz, N. Billot, X. Bonfils, J. Cabrera, S. Charnoz, A. Collier Cameron, C. Corral Van Damme, Sz Csizmadia, M. B. Davies, M. Deleuil, L. Delrez, T. De Roche, A. Erikson, A. Fortier, M. Fridlund, D. Futyan, D. Gandolfi, M. Gillon, M. Güdel, P. Gutermann, J. Hasiba, K. G. Isaak, L. Kiss, J. Laskar, A. Lecavelier Des Etangs, C. Lovis, D. Magrin, P. F.L. Maxted, M. Munari, V. Nascimbeni, R. Ottensamer, I. Pagano, E. Pallé, G. Peter, G. Piotto, D. Pollacco, D. Queloz, R. Ragazzoni, N. Rando, H. Rauer, I. Ribas, N. C. Santos, G. Scandariato, D. Ségransan, A. E. Simon, A. M.S. Smith, M. Steller, G. M. Szabó, N. Thomas, S. Udry, I. Walter, N. Walton
Abstract: Context. Gas giants orbiting close to hot and massive early-type stars can reach dayside temperatures that are comparable to those of the coldest stars. These aultra-hot Jupitersahave atmospheres made of ions and atomic species from molecular dissociation and feature strong day-to-night temperature gradients. Photometric observations at different orbital phases provide insights on the planetas atmospheric properties. Aims. We aim to analyse the photometric observations of WASP-189 acquired with the Characterising Exoplanet Satellite (CHEOPS) to derive constraints on the system architecture and the planetary atmosphere. Methods. We implemented a light-curve model suited for an asymmetric transit shape caused by the gravity-darkened photosphere of the fast-rotating host star. We also modelled the reflective and thermal components of the planetary flux, the effect of stellar oblateness and light-travel time on transit-eclipse timings, the stellar activity, and CHEOPS systematics. Results. From the asymmetric transit, we measure the size of the ultra-hot Jupiter WASP-189 b, R_p = 1.600-_0.016^+0.017R_J, with a precision of 1%, and the true orbital obliquity of the planetary system, Ψ_p = 89.6 ± 1.2deg (polar orbit). We detect no significant hotspot offset from the phase curve and obtain an eclipse depth of δ_ecl = 96.5_-5.0^+4.5appm, from which we derive an upper limit on the geometric albedo: A_g < 0.48. We also find that the eclipse depth can only be explained by thermal emission alone in the case of extremely inefficient energy redistribution. Finally, we attribute the photometric variability to the stellar rotation, either through superficial inhomogeneities or resonance couplings between the convective core and the radiative envelope. Conclusions. Based on the derived system architecture, we predict the eclipse depth in the upcoming Transiting Exoplanet Survey Satellite (TESS) observations to be up to ~165 ppm. High-precision detection of the eclipse in both CHEOPS and TESS passbands might help disentangle reflective and thermal contributions. We also expect the right ascension of the ascending node of the orbit to precess due to the perturbations induced by the stellar quadrupole moment J2 (oblateness).
Organisation(s): Department of Astrophysics
External organisation(s): Université de Genève, Universität Bern, Stockholm University, Centre national d'études spatiales (CNES), Université de Liège, Universidade do Porto, University of Warwick, Ludwig-Maximilians-Universität München, Institute of Astrophysics of the Canary Islands, University of La Laguna, University of Turin, Osservatorio Astronomico, Österreichische Akademie der Wissenschaften (ÖAW), University of St. Andrews, Universitat Autònoma de Barcelona , Admatis Ltd., Spanish National Research Council (CSIC), European Space Astronomy Centre (ESA), Centre National de la Recherche Scientifique (CNRS), Grenoble, University of Grenoble Alpes, Deutsches Zentrum für Luft- und Raumfahrt e.V. (DLR), Université Paris VII - Paris-Diderot, Science and Operations Department - Science Division (SCI-SC), Lund University, Leiden University, Chalmers University of Technology, National Institute for Earth Sciences & Astronomy (INSU-CNRS), Eötvös Loránd Research Network, Université de recherche Paris Sciences et Lettres, Université Paris VI - Pierre-et-Marie-Curie, Keele University, INAF-Osservatorio Astrofisico di Catania, University of Padova, University of Cambridge, Eidgenössische Technische Hochschule Zürich, Technische Universität Berlin, Freie Universität Berlin (FU), Institute of Space Studies of Catalonia (IEEC), Eötvös Loránd University Budapest
Journal: Astronomy and Astrophysics
Volume: 659
No. of pages: 25
ISSN: 0004-6361
DOI: https://doi.org/10.1051/0004-6361/202142400
Publication date: 03-2022
Peer reviewed: Yes
Austrian Fields of Science 2012: 103003 Astronomy, 103004 Astrophysics, 103038 Space exploration
Keywords
ASJC Scopus subject areas: Astronomy and Astrophysics, Space and Planetary Science
Portal url: https://ucrisportal.univie.ac.at/en/publications/5d8fa17d-7eb6-4c18-9b5a-5e767451e303

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