Asymmetry in the atmosphere of the ultra-hot Jupiter WASP-76 b***

Author(s): O. D.S. Demangeon, P. E. Cubillos, V. Singh, T. G. Wilson, L. Carone, A. Bekkelien, A. Deline, D. Ehrenreich, P. F.L. Maxted, B. O. Demory, T. Zingales, M. Lendl, A. Bonfanti, S. G. Sousa, A. Brandeker, Y. Alibert, R. Alonso, J. Asquier, T. Bárczy, D. Barrado Navascues, S. C.C. Barros, W. Baumjohann, M. Beck, T. Beck, W. Benz, N. Billot, F. Biondi, L. Borsato, Ch Broeg, M. Buder, A. Collier Cameron, Sz Csizmadia, M. B. Davies, M. Deleuil, L. Delrez, A. Erikson, A. Fortier, L. Fossati, M. Fridlund, D. Gandolfi, M. Gillon, M. Güdel, M. N. Günther, A. Heitzmann, Ch Helling, S. Hoyer, K. G. Isaak, L. L. Kiss, K. W.F. Lam, J. Laskar, A. Lecavelier des Etangs, D. Magrin, M. Mecina, Ch Mordasini, 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, M. Rieder, S. Salmon, N. C. Santos, G. Scandariato, D. Ségransan, A. E. Simon, A. M.S. Smith, M. Stalport, Gy M. Szabó, N. Thomas, S. Udry, V. Van Grootel, J. Venturini, E. Villaver, N. A. Walton
Abstract: Context. WASP-76 b has been a recurrent subject of study since the detection of a signature in high-resolution transit spectroscopy data indicating an asymmetry between the two limbs of the planet. The existence of this asymmetric signature has been confirmed by multiple studies, but its physical origin is still under debate. In addition, it contrasts with the absence of asymmetry reported in the infrared (IR) phase curve. Aims. We provide a more comprehensive dataset of WASP-76 b with the goal of drawing a complete view of the physical processes at work in this atmosphere. In particular, we attempt to reconcile visible high-resolution transit spectroscopy data and IR broadband phase curves. Methods. We gathered 3 phase curves, 20 occultations, and 6 transits for WASP-76 b in the visible with the CHEOPS space telescope. We also report the analysis of three unpublished sectors observed by the TESS space telescope (also in the visible), which represents 34 phase curves. Results. WASP-76 b displays an occultation of 260 ± 11 and 152 ± 10 ppm in TESS and CHEOPS bandpasses respectively. Depending on the composition assumed for the atmosphere and the data reduction used for the IR data, we derived geometric albedo estimates that range from 0.05 ± 0.023 to 0.146 ± 0.013 and from <0.13 to 0.189 ± 0.017 in the CHEOPS and TESS bandpasses, respectively. As expected from the IR phase curves, a low-order model of the phase curves does not yield any detectable asymmetry in the visible either. However, an empirical model allowing for sharper phase curve variations offers a hint of a flux excess before the occultation, with an amplitude of ∼40 ppm, an orbital offset of ∼−30^◦, and a width of ∼20^◦. We also constrained the orbital eccentricity of WASP-76 b to a value lower than 0.0067, with a 99.7% confidence level. This result contradicts earlier proposed scenarios aimed at explaining the asymmetry observed in high-resolution transit spectroscopy. Conclusions. In light of these findings, we hypothesise that WASP-76 b could have night-side clouds that extend predominantly towards its eastern limb. At this limb, the clouds would be associated with spherical droplets or spherically shaped aerosols of an unknown species, which would be responsible for a glory effect in the visible phase curves.
Organisation(s): Department of Astrophysics
External organisation(s): Universidade do Porto, INAF-Osservatorio Astrofisico di Torino, Österreichische Akademie der Wissenschaften (ÖAW), INAF-Osservatorio Astrofisico di Catania, University of Warwick, Université de Genève, Keele University, Universität Bern, University of Padova, Osservatorio Astronomico, Stockholm University, 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), Max-Planck-Institut für extraterrestrische Physik, Deutsches Zentrum für Luft- und Raumfahrt e.V. (DLR), 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, Université Paris VI - Pierre-et-Marie-Curie, Eidgenössische Technische Hochschule Zürich, University of Cambridge, 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: 684
No. of pages: 35
ISSN: 0004-6361
DOI: https://doi.org/10.1051/0004-6361/202348270
Publication date: 04-2024
Peer reviewed: Yes
Austrian Fields of Science 2012: 103003 Astronomy, 103004 Astrophysics
Keywords
ASJC Scopus subject areas: Astronomy and Astrophysics, Space and Planetary Science
Portal url: https://ucrisportal.univie.ac.at/en/publications/39e9229f-9ed2-4185-895e-9332828cdb35

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