CHEOPS geometric albedo of the hot Jupiter HD 209458 b

Author(s): A. Brandeker, K. Heng, M. Lendl, J. A. Patel, B. M. Morris, C. Broeg, P. Guterman, M. Beck, P. F.L. Maxted, O. Demangeon, L. Delrez, B. O. Demory, D. Kitzmann, N. C. Santos, V. Singh, Y. Alibert, R. Alonso, G. Anglada, T. Bárczy, D. Barrado y Navascues, S. C.C. Barros, W. Baumjohann, T. Beck, W. Benz, N. Billot, X. Bonfils, G. Bruno, J. Cabrera, S. Charnoz, A. Collier Cameron, C. Corral van Damme, Sz Csizmadia, M. B. Davies, M. Deleuil, A. Deline, D. Ehrenreich, A. Erikson, J. Farinato, A. Fortier, L. Fossati, M. Fridlund, D. Gandolfi, M. Gillon, M. Güdel, S. Hoyer, K. G. Isaak, L. Kiss, J. Laskar, A. Lecavelier des Etangs, C. Lovis, A. Luntzer, D. Magrin, V. Nascimbeni, G. Olofsson, R. Ottensamer, I. Pagano, E. Pallé, G. Peter, G. Piotto, D. Pollacco, D. Queloz, R. Ragazzoni, N. Rando, H. Rauer, I. Ribas, G. Scandariato, D. Ségransan, A. E. Simon, A. M.S. Smith, S. G. Sousa, M. Steller, G. M. Szabó, N. Thomas, S. Udry, V. van Grootel, N. Walton, D. Wolter
Abstract: We report the detection of the secondary eclipse of the hot Jupiter HD 209458 b in optical/visible light using the CHEOPS space telescope. Our measurement of 20.4^+3.2_-3.3 parts per million translates into a geometric albedo of A_g = 0.096 ± 0.016. The previously estimated dayside temperature of about 1500 K implies that our geometric albedo measurement consists predominantly of reflected starlight and is largely uncontaminated by thermal emission. This makes the present result one of the most robust measurements of A_g for any exoplanet. Our calculations of the bandpass-integrated geometric albedo demonstrate that the measured value of A_g is consistent with a cloud-free atmosphere, where starlight is reflected via Rayleigh scattering by hydrogen molecules, and the water and sodium abundances are consistent with stellar metallicity. We predict that the bandpass-integrated TESS geometric albedo is too faint to detect and that a phase curve of HD 209458 b observed by CHEOPS would have a distinct shape associated with Rayleigh scattering if the atmosphere is indeed cloud free.
Organisation(s): Department of Astrophysics
External organisation(s): Stockholm University, Universität Bern, University of Warwick, Université de Genève, Aix-Marseille Université, National Institute for Earth Sciences & Astronomy (INSU-CNRS), Keele University, Universidade do Porto, Université de Liège, Osservatorio Astronomico, Institute of Astrophysics of the Canary Islands, University of La Laguna, Spanish National Research Council (CSIC), Institute of Space Studies of Catalonia (IEEC), Admatis Ltd., European Space Astronomy Centre (ESA), Österreichische Akademie der Wissenschaften (ÖAW), University of Grenoble Alpes, Deutsches Zentrum für Luft- und Raumfahrt e.V. (DLR), Université Paris VII - Paris-Diderot, University of St. Andrews, Science and Operations Department - Science Division (SCI-SC), Lund University, Leiden University, Chalmers University of Technology, University of Turin, Eötvös Loránd Research Network, Eötvös Loránd University Budapest, Université de recherche Paris Sciences et Lettres, Université Paris VI - Pierre-et-Marie-Curie, INAF-Osservatorio Astrofisico di Catania, University of Padova, University of Cambridge, Eidgenössische Technische Hochschule Zürich, Technische Universität Berlin, Freie Universität Berlin (FU)
Journal: Astronomy and Astrophysics
Volume: 659
No. of pages: 8
ISSN: 0004-6361
DOI: https://doi.org/10.1051/0004-6361/202243082
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/dd4f2d40-8e19-4a9f-aa88-c27517d34ca4

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