Uncovering the true periods of the young sub-Neptunes orbiting TOI-2076

Author(s): H. P. Osborn, A. Bonfanti, D. Gandolfi, C. Hedges, A. Leleu, A. Fortier, D. Futyan, P. Gutermann, P. F.L. Maxted, L. Borsato, K. A. Collins, J. Gomes Da Silva, Y. Gomez Maqueo Chew, M. J. Hooton, M. Lendl, H. Parviainen, S. Salmon, N. Schanche, L. M. Serrano, S. G. Sousa, A. Tuson, S. Ulmer-Moll, V. Van Grootel, R. D. Wells, T. G. Wilson, Y. Alibert, R. Alonso, G. Anglada, J. Asquier, D. Barrado Y Navascues, W. Baumjohann, T. Beck, W. Benz, F. Biondi, X. Bonfils, F. Bouchy, A. Brandeker, C. Broeg, T. Barczy, S. C.C. Barros, J. Cabrera, S. Charnoz, A. Collier Cameron, S. Csizmadia, M. B. Davies, M. Deleuil, L. Delrez, B. O. Demory, D. Ehrenreich, A. Erikson, L. Fossati, M. Fridlund, M. Gillon, M. A. Gomez-Munoz, M. Gudel, K. Heng, S. Hoyer, K. G. Isaak, L. Kiss, J. Laskar, A. Lecavelier Des Etangs, C. Lovis, D. Magrin, L. Malavolta, J. McCormac, V. Nascimbeni, G. Olofsson, R. Ottensamer, I. Pagano, E. Palle, G. Peter, D. Piazza, G. Piotto, D. Pollacco, D. Queloz, R. Ragazzoni, N. Rando, H. Rauer, C. Reimers, I. Ribas, O. D.S. Demangeon, A. M.S. Smith, L. Sabin, N. Santos, G. Scandariato, U. Schroffenegger, R. P. Schwarz, A. Shporer, A. E. Simon, M. Steller, G. M. Szabo, D. Segransan, N. Thomas, S. Udry, I. Walter, N. Walton
Abstract: Context. TOI-2076 is a transiting three-planet system of sub-Neptunes orbiting a bright (G = 8.9 mag), young (340 ±80 Myr) K-type star. Although a validated planetary system, the orbits of the two outer planets were unconstrained as only two non-consecutive transits were seen in TESS photometry. This left 11 and 7 possible period aliases for each. Aims. To reveal the true orbits of these two long-period planets, precise photometry targeted on the highest-probability period aliases is required. Long-term monitoring of transits in multi-planet systems can also help constrain planetary masses through TTV measurements. Methods. We used the MonoTools package to determine which aliases to follow, and then performed space-based and ground-based photometric follow-up of TOI-2076 c and d with CHEOPS, SAINT-EX, and LCO telescopes. Results. CHEOPS observations revealed a clear detection for TOI-2076 c at P = 21.01538+0.00084 -0.00074 d, and allowed us to rule out three of the most likely period aliases for TOI-2076 d. Ground-based photometry further enabled us to rule out remaining aliases and confirm the P = 35.12537 ±0.00067 d alias. These observations also improved the radius precision of all three sub-Neptunes to 2.518 ±0.036, 3.497 ±0.043, and 3.232 ±0.063 R⊕;. Our observations also revealed a clear anti-correlated TTV signal between planets b and c likely caused by their proximity to the 2:1 resonance, while planets c and d appear close to a 5:3 period commensurability, although model degeneracy meant we were unable to retrieve robust TTV masses. Their inflated radii, likely due to extended H-He atmospheres, combined with low insolation makes all three planets excellent candidates for future comparative transmission spectroscopy with JWST.
Organisation(s): Department of Astrophysics
External organisation(s): Universität Bern, Massachusetts Institute of Technology, Österreichische Akademie der Wissenschaften (ÖAW), University of Turin, Bay Area Environmental Research Institute, National Aeronautics & Space Administration (NASA), Université de Genève, Aix-Marseille Université, National Institute for Earth Sciences & Astronomy (INSU-CNRS), Keele University, Osservatorio Astronomico, Harvard-Smithsonian Center for Astrophysics, Universidade do Porto, Universidad Nacional Autonoma de Mexico, Institute of Astrophysics of the Canary Islands, University of La Laguna, University of Cambridge, Université de Liège, University of St. Andrews, Spanish National Research Council (CSIC), Universitat Autònoma de Barcelona , Institute of Space Studies of Catalonia (IEEC), Science and Operations Department - Science Division (SCI-SC), European Space Astronomy Centre (ESA), Max-Planck-Institut für extraterrestrische Physik, University of Grenoble Alpes, Stockholm University, Admatis Ltd., Deutsches Zentrum für Luft- und Raumfahrt e.V. (DLR), Université de Paris, Lund University, Leiden University, Chalmers University of Technology, University of Warwick, Eötvös Loránd Research Network, Eötvös Loránd University Budapest, Université de recherche Paris Sciences et Lettres, Université Paris VI - Pierre-et-Marie-Curie, University of Padova, INAF-Osservatorio Astrofisico di Catania, Technische Universität Berlin, Patashnick Voorheesville Observatory
Journal: Astronomy and Astrophysics
Volume: 664
No. of pages: 17
ISSN: 0004-6361
DOI: https://doi.org/10.1051/0004-6361/202243065
Publication date: 08-2022
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/fdf3aad1-4ed9-46c1-90b8-5abc5652f929

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