CHEOPS observations of KELT-20 b/MASCARA-2 b

Author(s): V. Singh, G. Scandariato, A. M.S. Smith, P. E. Cubillos, M. Lendl, N. Billot, A. Fortier, D. Queloz, S. G. Sousa, Sz Csizmadia, A. Brandeker, L. Carone, T. G. Wilson, B. Akinsanmi, J. A. Patel, A. Krenn, O. D.S. Demangeon, G. Bruno, I. Pagano, M. J. Hooton, J. Cabrera, N. C. Santos, Y. Alibert, R. Alonso, J. Asquier, T. Bárczy, D. Barrado Navascues, S. C.C. Barros, W. Baumjohann, M. Beck, T. Beck, W. Benz, M. Bergomi, A. Bonfanti, X. Bonfils, L. Borsato, C. Broeg, S. Charnoz, A. Collier Cameron, M. B. Davies, M. Deleuil, A. Deline, L. Delrez, B. O. Demory, D. Ehrenreich, A. Erikson, L. Fossati, M. Fridlund, D. Gandolfi, M. Gillon, M. Güdel, M. N. Günther, J. V. Harre, A. Heitzmann, Ch Helling, S. Hoyer, K. G. Isaak, L. L. Kiss, K. W.F. Lam, J. Laskar, A. Lecavelier Des Etangs, D. Magrin, P. F.L. Maxted, H. Mischler, C. Mordasini, V. Nascimbeni, G. Olofsson, R. Ottensamer, E. Pallé, G. Peter, G. Piotto, D. Pollacco, R. Ragazzoni, N. Rando, H. Rauer, I. Ribas, S. Salmon, D. Ségransan, A. E. Simon, M. Stalport, M. Steinberger, Gy M. Szabó, N. Thomas, S. Udry, B. Ulmer, V. Van Grootel, J. Venturini, E. Villaver, N. A. Walton, T. Zingales
Abstract: Context. Occultations are windows of opportunity to indirectly peek into the dayside atmosphere of exoplanets. High-precision transit events provide information on the spin-orbit alignment of exoplanets around fast-rotating hosts. Aims. We aim to precisely measure the planetary radius and geometric albedo of the ultra-hot Jupiter (UHJ) KELT-20 b along with the spin-orbit alignment of the system. Methods. We obtained optical high-precision transits and occultations of KELT-20 b using CHEOPS observations in conjunction with simultaneous TESS observations. We interpreted the occultation measurements together with archival infrared observations to measure the planetary geometric albedo and dayside temperatures. We further used the host star's gravity-darkened nature to measure the system's obliquity. Results. We present a time-averaged precise occultation depth of 82 ± 6 ppm measured with seven CHEOPS visits and 131_-7⁺⁸ from the analysis of all available TESS photometry. Using these measurements, we precisely constrain the geometric albedo of KELT-20 b to 0.26 ± 0.04 and the brightness temperature of the dayside hemisphere to 2566_-80⁺⁷⁷ K. Assuming Lambertian scattering law, we constrain the Bond albedo to 0.36_-0.05^+0.04 along with a minimal heat transfer to the night side (Ïμ = 0.14_-0.10^+0.13). Furthermore, using five transit observations we provide stricter constraints of 3 9 ± 1 1 deg on the sky-projected obliquity of the system. Conclusions. The aligned orbit of KELT-20 b is in contrast to previous CHEOPS studies that have found strongly inclined orbits for planets orbiting other A-type stars. The comparably high planetary geometric albedo of KELT-20 b corroborates a known trend of strongly irradiated planets being more reflective. Finally, we tentatively detect signs of temporal variability in the occultation depths, which might indicate variable cloud cover advecting onto the planetary day side.
Organisation(s): Department of Astrophysics
External organisation(s): INAF-Osservatorio Astrofisico di Catania, Deutsches Zentrum für Luft- und Raumfahrt e.V. (DLR), INAF-Osservatorio Astrofisico di Torino, Österreichische Akademie der Wissenschaften (ÖAW), Université de Genève, Universität Bern, Eidgenössische Technische Hochschule Zürich, University of Cambridge, Universidade do Porto, Stockholm University, University of Warwick, Institute of Astrophysics of the Canary Islands, University of La Laguna, Science and Operations Department - Science Division (SCI-SC), Admatis Ltd., European Space Astronomy Centre (ESA), Osservatorio Astronomico, University of Grenoble Alpes, Université de Paris, University of St. Andrews, Lund University, Aix-Marseille Université, Université de Liège, Leiden University, Chalmers University of Technology, University of Turin, Technische Universität Graz, Eötvös Loránd Research Network, Eötvös Loránd University Budapest, Université de recherche Paris Sciences et Lettres, Centre National De La Recherche Scientifique (CNRS), Keele University, University of Padova, Technische Universität Berlin, Freie Universität Berlin (FU), Spanish National Research Council (CSIC), Institute of Space Studies of Catalonia (IEEC), HUN-REN Hungarian Research Network
Journal: Astronomy and Astrophysics
Volume: 683
No. of pages: 25
ISSN: 0004-6361
DOI: https://doi.org/10.1051/0004-6361/202347533
Publication date: 03-2024
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/72cc124c-c63b-4443-9ebc-db246bf14bc1

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