Brandeker, A, Heng, K, Lendl, M, Patel, JA, Morris, BM, Broeg, C, Guterman, P, Beck, M, Maxted, PFL, Demangeon, O, Delrez, L, Demory, B-O, Kitzmann, D, Santos, NC, Singh, V, Alibert, Y, Alonso, R, Anglada, G, Bárczy, T, Barrado y Navascues, D, Barros, SCC, Baumjohann, W, Beck, T, Benz, W, Billot, N, Bonfils, X, Bruno, G, Cabrera, J, Charnoz, S, Collier Cameron, A, Corral van Damme, C, Csizmadia, S, Davies, MB, Deleuil, M, Deline, A, Ehrenreich, D, Erikson, A, Farinato, J, Fortier, A, Fossati, L, Fridlund, M, Gandolfi, D, Gillon, M, Güdel, M, Hoyer, S, Isaak, KG, Kiss, L, Laskar, J, Lecavelier des Etangs, A, Lovis, C, Luntzer, A, Magrin, D, Nascimbeni, V, Olofsson, G, Ottensamer, R, Pagano, I, Pallé, E, Peter, G, Piotto, G, Pollacco, D, Queloz, D, Ragazzoni, R, Rando, N, Rauer, H, Ribas, I, Scandariato, G, Ségransan, D, Simon, AE, Smith, AMS, Sousa, SG, Steller, M, Szabó, GM, Thomas, N, Udry, S, Van Grootel, V, Walton, N and Wolter, D (2022) CHEOPS geometric albedo of the hot Jupiter HD 209458 b. Astronomy & Astrophysics, 659. L4 - L4. ISSN 0004-6361

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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(-3.3)(+3.2) 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 bandpassintegrated 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.

Item Type: Article
Additional Information: The final version of this publication is available directly from the publishers at
Uncontrolled Keywords: techniques: photometric / planetary systems / planets and satellites: atmospheres / planets and satellites: individual: HD 209458 b
Subjects: Q Science > QB Astronomy
Divisions: Faculty of Natural Sciences > School of Chemical and Physical Sciences
Depositing User: Symplectic
Date Deposited: 05 Apr 2022 12:11
Last Modified: 22 Apr 2022 15:17

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