Characterization of the HD 108236 system with CHEOPS and TESS Confirmation of a fifth transiting planet

Author(s): Sergio Hoyer, A. Bonfanti, A. Leleu, L. Acuna, Luisa Maria Serrano, Manuel Güdel, A. Bekkelien, Christopher Broeg, Hans-Gustav Florén, Didier Queloz, Thomas G. Wilson, S. G. Sousa, M. J. Hooton, V. Adibekyan, Yann Alibert, Claudio R. Alonso, G. Anglada, J. Asquier, T. Bárczy, David Barrado, S. C. C. Barros, W. Baumjohann, M. Beck, T. Beck, W. Benz, N. Billot, F. Biondi, X. Bonfils, A. Brandeker, Juan Cabrera, S. Charnoz, A. Collier Cameron, Szilard Csizmadia, M. B. Davies, L. Delrez, O. D. S. Demangeon, B. O. Demory, D. Ehrenreich, Anders Erikson, A. Fortier, L. Fossati, M. Fridlund, Davide Gandolfi, Michael Gillon, Manuel Güdel, N. C. Hara, Kevin Heng, K. G. Isaak, Jon M. Jenkins, Laszlo Kiss, J. Laskar, D. W. Latham, Alain Lecavelier Des Etangs, M. Lendl, Christophe Lovis, Armin Luntzer, D. Magrin, P. F. L. Maxted, Valerio Nascimbeni, Göran Olofsson, Roland Ottensamer, Isabella Pagano, E. Pallé, C. M. Persson, G. Peter, D. Piazza, Giampaolo P. Piotto, D. Pollacco, R. Ragazzoni, N. Rando, Heike Rauer, Ignasi Ribas, George R. Ricker, S. Salmon, Nuno C. Santos, Gaetano Scandariato, Sara Seager, Damien Ségransan, A. E. Simon, A. M. S. Smith, Manfred Steller, Gy M. Szabó, N. Thomas, Joseph D. Twicken, Stephane Udry, Valerie Van Grootel, Roland K. Vanderspek, N. A. Walton, K. Westerdorff, Joshua N. Winn
Abstract: Context. The HD 108236 system was first announced with the detection of four small planets based on TESS data. Shortly after, the transit of an additional planet with a period of 29.54 d was serendipitously detected by CHEOPS. In this way, HD 108236 (V = 9.2) became one of the brightest stars known to host five small transiting planets (Rp < 3 Ro˙). Aims. We characterize the planetary system by using all the data available from CHEOPS and TESS space missions. We use the flexible pointing capabilities of CHEOPS to follow up the transits of all the planets in the system, including the fifth transiting body. Methods. After updating the host star parameters by using the results from Gaia eDR3, we analyzed 16 and 43 transits observed by CHEOPS and TESS, respectively, to derive the planets' physical and orbital parameters. We carried out a timing analysis of the transits of each of the planets of HD 108236 to search for the presence of transit timing variations. Results. We derived improved values for the radius and mass of the host star (R∗ = 0.876 ± 0.007 R0 and M∗ = 0.867-0.046+0.047M). We confirm the presence of the fifth transiting planet f in a 29.54 d orbit. Thus, the HD 108236 system consists of five planets of Rb = 1.587±0.028, Rc = 2.122±0.025, Rd = 2.629 ± 0.031, Re = 3.008 ± 0.032, and Rf = 1.89 ± 0.04 [Ro˙]. We refine the transit ephemeris for each planet and find no significant transit timing variations for planets c, d, and e. For planets b and f, instead, we measure significant deviations on their transit times (up to 22 and 28 min, respectively) with a non-negligible dispersion of 9.6 and 12.6 min in their time residuals. Conclusions. We confirm the presence of planet f and find no significant evidence for a potential transiting planet in a 10.9 d orbital period, as previously suggested. Further monitoring of the transits, particularly for planets b and f, would confirm the presence of the observed transit time variations. HD 108236 thus becomes a key multi-planetary system for the study of formation and evolution processes. The reported precise results on the planetary radii - together with a profuse RV monitoring - will allow for an accurate characterization of the internal structure of these planets.
Organisation(s): Department of Astrophysics
External organisation(s): Universität Bern, University of Turin, University of Cambridge, Stockholm University, University of St. Andrews, Spanish National Research Council (CSIC), Institute of Astrophysics of the Canary Islands, Institute of Space Studies of Catalonia (IEEC), Science and Operations Department - Science Division (SCI-SC), Admatis Ltd., Universidade do Porto, Osservatorio Astronomico, University of Grenoble Alpes, Université de Paris, Aix-Marseille Université, Université de Genève, Lund University, Harvard-Smithsonian Center for Astrophysics, Sorbonne Université, Österreichische Akademie der Wissenschaften (ÖAW), Eidgenössische Technische Hochschule Zürich, University of La Laguna, Deutsches Zentrum für Luft- und Raumfahrt e.V. (DLR), Université de Liège, Leiden University, Chalmers University of Technology, University of Warwick, National Aeronautics & Space Administration (NASA), Hungarian Academy of Sciences, Eötvös Loránd University Budapest, Université Paris IV - Paris-Sorbonne, Paris Observatory, Keele University, INAF-Osservatorio Astrofisico di Catania, University of Padova, Technische Universität Berlin, Massachusetts Institute of Technology, Max-Planck-Institut für extraterrestrische Physik, Freie Universität Berlin (FU), SETI Institute, NASA Ames Research Center
Journal: Astronomy & Astrophysics
Volume: 668
ISSN: 0004-6361
DOI: https://doi.org/10.1051/0004-6361/202243720
Publication date: 12-2022
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/d3de861c-5a24-4d96-b728-33296010f00c

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