Investigating the architecture and internal structure of the TOI-561 system planets with CHEOPS, HARPS-N, and TESS

Author(s): G. Lacedelli, T. G. Wilson, L. Malavolta, M. J. Hooton, A. Collier Cameron, Y. Alibert, A. Mortier, A. Bonfanti, R. D. Haywood, S. Hoyer, G. Piotto, A. Bekkelien, A. M. Vanderburg, W. Benz, X. Dumusque, A. Deline, M. Lopez-Morales, L. Borsato, K. Rice, L. Fossati, D. W. Latham, A. Brandeker, E. Poretti, S. G. Sousa, A. Sozzetti, S. Salmon, C. J. Burke, V. Van Grootel, M. M. Fausnaugh, V. Adibekyan, C. X. Huang, H. P. Osborn, A. J. Mustill, E. Palle, V. Bourrier, V. Nascimbeni, R. Alonso, G. Anglada, T. Barczy, D. Barrado Y Navascues, S. C.C. Barros, W. Baumjohann, M. Beck, T. Beck, N. Billot, X. Bonfils, C. Broeg, L. A. Buchhave, J. Cabrera, S. Charnoz, R. Cosentino, S. Csizmadia, M. B. Davies, M. Deleuil, L. Delrez, O. Demangeon, B. O. Demory, D. Ehrenreich, A. Erikson, E. Esparza-Borges, H. G. Floren, A. Fortier, M. Fridlund, D. Futyan, D. Gandolfi, A. Ghedina, M. Gillon, M. Güdel, P. Guterman, A. Harutyunyan, K. Heng, K. G. Isaak, J. M. Jenkins, L. Kiss, J. Laskar, A. Lecavelier Des Etangs, M. Lendl, C. Lovis, D. Magrin, L. Marafatto, A. F. Martinez Fiorenzano, P. F.L. Maxted, M. Mayor, G. Micela, E. Molinari, F. Murgas, N. Narita, G. Olofsson, R. Ottensamer, I. Pagano, A. Pasetti, M. Pedani, F. A. Pepe, G. Peter, D. F. Phillips, D. Pollacco, D. Queloz, R. Ragazzoni, N. Rando, F. Ratti, H. Rauer, I. Ribas, N. C. Santos, D. Sasselov, G. Scandariato, S. Seager, D. Segransan, L. M. Serrano, A. E. Simon, A. M.S. Smith, M. Steinberger, M. Steller, Gy Szabo, N. Thomas, J. D. Twicken, S. Udry, N. Walton, J. N. Winn
Abstract: We present a precise characterization of the TOI-561 planetary system obtained by combining previously published data with TESS and CHEOPS photometry, and a new set of 62 HARPS-N radial velocities (RVs). Our joint analysis confirms the presence of four transiting planets, namely TOI-561 b (P = 0.45 d, R = 1.42 R_⊕, M = 2.0 M_⊕), c (P = 10.78 d, R = 2.91 R_⊕, M = 5.4 M_⊕), d (P = 25.7 d, R = 2.82 R_⊕, M = 13.2 M_⊕), and e (P = 77 d, R = 2.55 R_⊕, M = 12.6 R_⊕). Moreover, we identify an additional, long-period signal (>450 d) in the RVs, which could be due to either an external planetary companion or to stellar magnetic activity. The precise masses and radii obtained for the four planets allowed us to conduct interior structure and atmospheric escape modelling. TOI-561 b is confirmed to be the lowest density (ρ_b = 3.8 ± 0.5 g cm^-3) ultra-short period (USP) planet known to date, and the low metallicity of the host star makes it consistent with the general bulk density-stellar metallicity trend. According to our interior structure modelling, planet b has basically no gas envelope, and it could host a certain amount of water. In contrast, TOI-561 c, d, and e likely retained an H/He envelope, in addition to a possibly large water layer. The inferred planetary compositions suggest different atmospheric evolutionary paths, with planets b and c having experienced significant gas loss, and planets d and e showing an atmospheric content consistent with the original one. The uniqueness of the USP planet, the presence of the long-period planet TOI-561 e, and the complex architecture make this system an appealing target for follow-up studies.
Organisation(s): Department of Astrophysics
External organisation(s): University of Padova, Osservatorio Astronomico, University of St. Andrews, Universität Bern, University of Cambridge, Österreichische Akademie der Wissenschaften (ÖAW), University of Exeter, Aix-Marseille Université, Université de Genève, Massachusetts Institute of Technology, University of Wisconsin, Madison, Harvard-Smithsonian Center for Astrophysics, University of Edinburgh, Stockholm University, Instituto Nazionale die Astrofisica (INAF), INAF Osservatorio Astronomico di Brera, Universidade do Porto, INAF-Osservatorio Astrofisico di Torino, Université de Liège, University of Southern Queensland, Lund Observatory, Institute of Astrophysics of the Canary Islands, University of La Laguna, Spanish National Research Council (CSIC), Institute of Space Studies of Catalonia (IEEC), Admatis Ltd., European Space Astronomy Centre (ESA), University of Grenoble Alpes, Technical University of Denmark (DTU), Deutsches Zentrum für Luft- und Raumfahrt e.V. (DLR), Université de Paris, Lund University, Leiden University, Chalmers University of Technology, University of Turin, National Institute for Earth Sciences & Astronomy (INSU-CNRS), University of Warwick, Science and Operations Department - Science Division (SCI-SC), National Aeronautics & Space Administration (NASA), Eötvös Loránd Research Network, Eötvös Loránd University Budapest, Université de recherche Paris Sciences et Lettres, Université Paris VI - Pierre-et-Marie-Curie, Keele University, INAF -Osservatorio Astronomico di Cagliari, University of Tokyo, National Institutes of Natural Sciences (NINS), INAF-Osservatorio Astrofisico di Catania, P&P Software GmbH, High Tech Center, Tägerwilen, 8274, Switzerland, Technische Universität Berlin, Freie Universität Berlin (FU), SETI Institute, Princeton University
Journal: Monthly Notices of the Royal Astronomical Society
Volume: 511
Pages: 4551-4571
No. of pages: 21
ISSN: 0035-8711
DOI: https://doi.org/10.1093/mnras/stac199
Publication date: 04-2022
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/38ff5daf-0221-43f5-977b-75697901b1c0

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