Investigating the visible phase-curve variability of 55 Cnc e

Author(s): E. A. Meier Valdés, B. M. Morris, B. O. Demory, A. Brandeker, D. Kitzmann, W. Benz, A. Deline, H. G. Florén, S. G. Sousa, V. Bourrier, V. Singh, K. Heng, A. Strugarek, D. J. Bower, N. Jäggi, L. Carone, M. Lendl, K. Jones, A. V. Oza, O. D.S. Demangeon, Y. Alibert, R. Alonso, G. Anglada, J. Asquier, T. Bárczy, D. Barrado Navascues, S. C.C. Barros, W. Baumjohann, M. Beck, T. Beck, N. Billot, X. Bonfils, L. Borsato, C. Broeg, J. Cabrera, S. Charnoz, A. Collier Cameron, Sz Csizmadia, P. E. Cubillos, M. B. Davies, M. Deleuil, L. Delrez, D. Ehrenreich, A. Erikson, A. Fortier, L. Fossati, M. Fridlund, D. Gandolfi, M. Gillon, M. Güdel, M. N. Günther, S. Hoyer, K. G. Isaak, L. L. Kiss, J. Laskar, A. Lecavelier Des Etangs, C. Lovis, D. Magrin, P. F.L. Maxted, C. 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, N. C. Santos, M. Sarajlic, G. Scandariato, D. Ségransan, D. Sicilia, A. E. Simon, A. M.S. Smith, M. Steller, Gy M. Szabó, N. Thomas, S. Udry, B. Ulmer, V. Van Grootel, J. Venturini, N. A. Walton, T. G. Wilson, D. Wolter
Abstract: Context. 55 Cnc e is an ultra-short period super-Earth transiting a Sun-like star. Previous observations in the optical range detected a time-variable flux modulation that is phased with the planetary orbital period, whose amplitude is too large to be explained by reflected light and thermal emission alone. Aims. The goal of the study is to investigate the origin of the variability and timescale of the phase-curve modulation in 55 Cnc e. To this end, we used the CHaracterising ExOPlanet Satellite (CHEOPS), whose exquisite photometric precision provides an opportunity to characterise minute changes in the phase curve from one orbit to the next. Methods. CHEOPS observed 29 individual visits of 55 Cnc e between March 2020 and February 2022. Based on these observations, we investigated the different processes that could be at the origin of the observed modulation. In particular, we built a toy model to assess whether a circumstellar torus of dust driven by radiation pressure and gravity might match the observed flux variability timescale. Results. We find that the phase-curve amplitude and peak offset of 55 Cnc e do vary between visits. The sublimation timescales of selected dust species reveal that silicates expected in an Earth-like mantle would not survive long enough to explain the observed phase-curve modulation. We find that silicon carbide, quartz, and graphite are plausible candidates for the circumstellar torus composition because their sublimation timescales are long. Conclusions. The extensive CHEOPS observations confirm that the phase-curve amplitude and offset vary in time. We find that dust could provide the grey opacity source required to match the observations. However, the data at hand do not provide evidence that circumstellar material with a variable grain mass per unit area causes the observed variability. Future observations with the James Webb Space Telescope (JWST) promise exciting insights into this iconic super-Earth.
Organisation(s): Department of Astrophysics
External organisation(s): Universität Bern, Space Telescope Science Institute, Stockholm University, Université de Genève, Universidade do Porto, INAF-Osservatorio Astrofisico di Catania, Ludwig-Maximilians-Universität München, University of Warwick, Université Paris Saclay, Österreichische Akademie der Wissenschaften (ÖAW), California Institute of Technology (Caltech), Institute of Astrophysics of the Canary Islands, University of La Laguna, Spanish National Research Council (CSIC), Institute of Space Studies of Catalonia (IEEC), Science and Operations Department - Science Division (SCI-SC), Admatis Ltd., European Space Astronomy Centre (ESA), University of Grenoble Alpes, Osservatorio Astronomico, Deutsches Zentrum für Luft- und Raumfahrt e.V. (DLR), Université de Paris, University of St. Andrews, INAF-Osservatorio Astrofisico di Torino, Lund University, Aix-Marseille Université, Université de Liège, Leiden University, Chalmers University of Technology, Università degli Studi di Torino, Eötvös Loránd Research Network, Eötvös Loránd University Budapest, Université de recherche Paris Sciences et Lettres, Université Paris VI - Pierre-et-Marie-Curie, Keele University, University of Padova, Eidgenössische Technische Hochschule Zürich, University of Cambridge, Technische Universität Berlin, Freie Universität Berlin (FU)
Journal: Astronomy and Astrophysics
Volume: 677
No. of pages: 26
ISSN: 0004-6361
DOI: https://doi.org/10.1051/0004-6361/202346050
Publication date: 09-2023
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/8c96bf58-6d63-4bb4-ad87-0dd030958b60

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