Planetary systems; Stars: individual: TOI-178; Techniques: photometric; Neptune; Orbital periods; Planetary system; Property; Radial velocity; Star: individual: TOI-178; Stars: individual: proxima Centauri; Timing variations; Transit timing; Astronomy and Astrophysics; Space and Planetary Science; astro-ph.EP
Abstract :
[en] Context. The TOI-178 system consists of a nearby late K-dwarf transited by six planets in the super-Earth to mini-Neptune regime, with radii ranging from -1.1 to 2.9 R and orbital periods between 1.9 and 20.7 days. All planets but the innermost one form a chain of Laplace resonances. Mass estimates derived from a preliminary radial velocity (RV) dataset suggest that the planetary densities do not decrease in a monotonic way with the orbital distance to the star, contrary to what one would expect based on simple formation and evolution models. Aims. To improve the characterisation of this key system and prepare for future studies (in particular with JWST), we performed a detailed photometric study based on 40 new CHEOPS visits, one new TESS sector, and previously published CHEOPS, TESS, and NGTS data. Methods. First we updated the parameters of the host star using the new parallax from Gaia EDR3. We then performed a global analysis of the 100 transits contained in our data to refine the physical and orbital parameters of the six planets and study their transit timing variations (TTVs). We also used our extensive dataset to place constraints on the radii and orbital periods of potential additional transiting planets in the system. Results. Our analysis significantly refines the transit parameters of the six planets, most notably their radii, for which we now obtain relative precisions of -3%, with the exception of the smallest planet, b, for which the precision is 5.1%. Combined with the RV mass estimates, the measured TTVs allow us to constrain the eccentricities of planets c to g, which are found to be all below 0.02, as expected from stability requirements. Taken alone, the TTVs also suggest a higher mass for planet d than that estimated from the RVs, which had been found to yield a surprisingly low density for this planet. However, the masses derived from the current TTV dataset are very prior-dependent, and further observations, over a longer temporal baseline, are needed to deepen our understanding of this iconic planetary system.
Disciplines :
Space science, astronomy & astrophysics
Author, co-author :
Delrez, Laetitia ; Université de Liège - ULiège > Département d'astrophysique, géophysique et océanographie (AGO) > Exoplanets in Transit: Identification and Characterization
Leleu, A.; Observatoire Astronomique de l' Université de Genève, Versoix, Switzerland ; Physikalisches Institut, University of Bern, Bern, Switzerland
Brandeker, A.; Department of Astronomy, Stockholm University, AlbaNova University Center, Stockholm, Sweden
Gillon, Michaël ; Université de Liège - ULiège > Département d'astrophysique, géophysique et océanographie (AGO)
Hooton, M.J.; Physikalisches Institut, University of Bern, Bern, Switzerland ; Cavendish Laboratory, Cambridge, United Kingdom
Collier Cameron, A.; Centre for Exoplanet Science, Supa School of Physics and Astronomy, University of St Andrews, St Andrews, United Kingdom
Deline, A.; Observatoire Astronomique de l' Université de Genève, Versoix, Switzerland
Fortier, A.; Physikalisches Institut, University of Bern, Bern, Switzerland ; Center for Space and Habitability, University of Bern, Bern, Switzerland
Queloz, D.; Cavendish Laboratory, Cambridge, United Kingdom ; Eth Zurich, Department of Physics, Zurich, Switzerland
Bonfanti, A.; Space Research Institute, Austrian Academy of Sciences, Graz, Austria
Van Grootel, Valérie ; Université de Liège - ULiège > Département d'astrophysique, géophysique et océanographie (AGO) > Astrophysique stellaire théorique et astérosismologie
Wilson, T.G.; Centre for Exoplanet Science, Supa School of Physics and Astronomy, University of St Andrews, St Andrews, United Kingdom
Egger, J.A.; Physikalisches Institut, University of Bern, Bern, Switzerland
Alibert, Y.; Physikalisches Institut, University of Bern, Bern, Switzerland
Alonso, R.; Instituto de Astrofisica de Canarias, Tenerife, Spain ; Departamento de Astrofisica, Universidad de la Laguna, Tenerife, Spain
Anglada, G.; Institut de Ciencies de l' Espai (ICE CSIC), Campus Uab, Bellaterra, Spain ; Institut d' Estudis Espacials de Catalunya (IEEC), Barcelona, Spain
Asquier, J.; Estec, European Space Agency, Noordwijk, Netherlands
Bárczy, T.; Admatis, Miskolc, Hungary
Barrado Y Navascues, D.; Depto. de Astrofisica, Centro de Astrobiologia (CSIC-INTA), Esac Campus, Madrid, Spain
Barros, S.C.C.; Instituto de Astrofisica e Ciencias Do Espaco, Universidade Do Porto, Caup, Porto, Portugal ; Departamento de Fisica e Astronomia, Faculdade de Ciencias, Universidade Do Porto, Porto, Portugal
Baumjohann, W.; Space Research Institute, Austrian Academy of Sciences, Graz, Austria
Beck, M.; Observatoire Astronomique de l' Université de Genève, Versoix, Switzerland
Beck, T.; Physikalisches Institut, University of Bern, Bern, Switzerland
Benz, W.; Physikalisches Institut, University of Bern, Bern, Switzerland ; Center for Space and Habitability, University of Bern, Bern, Switzerland
Billot, N.; Observatoire Astronomique de l' Université de Genève, Versoix, Switzerland
Bonfils, X.; Université Grenoble Alpes, Cnrs, Ipag, Grenoble, France
Borsato, L.; Inaf, Osservatorio Astronomico di Padova, Padova, Italy
Broeg, C.; Physikalisches Institut, University of Bern, Bern, Switzerland ; Center for Space and Habitability, University of Bern, Bern, Switzerland
Buder, M.; Institute of Optical Sensor Systems, German Aerospace Center (DLR), Berlin, Germany
Cabrera, J.; Institute of Planetary Research, German Aerospace Center (DLR), Berlin, Germany
Cessa, V.; Physikalisches Institut, University of Bern, Bern, Switzerland
Charnoz, S.; Université de Paris, Institut de Physique du Globe de Paris, Cnrs, Paris, France
Csizmadia, Sz.; Institute of Planetary Research, German Aerospace Center (DLR), Berlin, Germany
Cubillos, P.E.; Space Research Institute, Austrian Academy of Sciences, Graz, Austria ; Inaf, Osservatorio Astrofisico di Torino, Pino Torinese, Italy
Davies, M.B.; Centre for Mathematical Sciences, Lund University, Box 118, Lund, Sweden
Deleuil, M.; Aix Marseille Univ., Cnrs, Cnes, Lam, Marseille, France
Demangeon, O.D.S.; Instituto de Astrofisica e Ciencias Do Espaco, Universidade Do Porto, Caup, Porto, Portugal ; Departamento de Fisica e Astronomia, Faculdade de Ciencias, Universidade Do Porto, Porto, Portugal
Demory, B.-O.; Physikalisches Institut, University of Bern, Bern, Switzerland ; Center for Space and Habitability, University of Bern, Bern, Switzerland
Ehrenreich, D.; Observatoire Astronomique de l' Université de Genève, Versoix, Switzerland ; Centre Vie dans l' Univers, Faculté des Sciences, Université de Genève, Genève, Switzerland
Erikson, A.; Institute of Planetary Research, German Aerospace Center (DLR), Berlin, Germany
Fossati, L.; Space Research Institute, Austrian Academy of Sciences, Graz, Austria
Fridlund, M.; Leiden Observatory, University of Leiden, Leiden, Netherlands ; Department of Space Earth and Environment, Chalmers University of Technology, Onsala Space Observatory, Onsala, Sweden
Gandolfi, D.; Dipartimento di Fisica, Universita Degli Studi di Torino, Torino, Italy
Güdel, M.; University of Vienna, Department of Astrophysics, Vienna, Austria
Hasiba, J.; Space Research Institute, Austrian Academy of Sciences, Graz, Austria
Hoyer, S.; Aix Marseille Univ., Cnrs, Cnes, Lam, Marseille, France
Isaak, K.G.; Science and Operations Department - Science Division (SCI-SC), Directorate of Science, European Space Agency (ESA), European Space Research and Technology Centre (ESTEC), Noordwijk, Netherlands
Jenkins, J.M.; Nasa Ames Research Center, Moffett Field, United States
Kiss, L.L.; Konkoly Observatory, Research Centre for Astronomy and Earth Sciences, Budapest, Hungary ; Elte Eötvös Loránd University, Institute of Physics, Pázmány Péter Sétány 1/A, Budapest, Hungary
Laskar, J.; Imcce, UMR8028 Cnrs, Observatoire de Paris, Psl Univ., Sorbonne Univ., Paris, France
Latham, D.W.; Center for Astrophysics Harvard & Smithsonian, Cambridge, United States
Lecavelier Des Etangs, A.; Institut d' Astrophysique de Paris, UMR7095 Cnrs, Université Pierre & Marie Curie, Paris, France
Lendl, M.; Observatoire Astronomique de l' Université de Genève, Versoix, Switzerland
Lovis, C.; Observatoire Astronomique de l' Université de Genève, Versoix, Switzerland
Luque, R.; Department of Astronomy and Astrophysics, University of Chicago, Chicago, United States
Magrin, D.; Inaf, Osservatorio Astronomico di Padova, Padova, Italy
Maxted, P.F.L.; Astrophysics Group, Keele University, Staffordshire, United Kingdom
Mordasini, C.; Physikalisches Institut, University of Bern, Bern, Switzerland ; Center for Space and Habitability, University of Bern, Bern, Switzerland
Nascimbeni, V.; Inaf, Osservatorio Astronomico di Padova, Padova, Italy
Olofsson, G.; Department of Astronomy, Stockholm University, AlbaNova University Center, Stockholm, Sweden
Ottensamer, R.; Department of Astrophysics, University of Vienna, Vienna, Austria
Pagano, I.; Inaf, Osservatorio Astrofisico di Catania, Catania, Italy
Pallé, E.; Instituto de Astrofisica de Canarias, Tenerife, Spain
Peter, G.; Institute of Optical Sensor Systems, German Aerospace Center (DLR), Berlin, Germany
Piotto, G.; Inaf, Osservatorio Astronomico di Padova, Padova, Italy ; Dipartimento di Fisica e Astronomia Galileo Galilei, Universita Degli Studi di Padova, Padova, Italy
Pollacco, D.; Department of Physics, University of Warwick, Coventry, United Kingdom
Ragazzoni, R.; Inaf, Osservatorio Astronomico di Padova, Padova, Italy ; Dipartimento di Fisica e Astronomia Galileo Galilei, Universita Degli Studi di Padova, Padova, Italy
Rando, N.; Estec, European Space Agency, Noordwijk, Netherlands
Rauer, H.; Institute of Planetary Research, German Aerospace Center (DLR), Berlin, Germany ; Zentrum für Astronomie und Astrophysik, Technische Universität Berlin, Berlin, Germany ; Institut für Geologische Wissenschaften, Freie Universität Berlin, Berlin, Germany
Ribas, I.; Institut de Ciencies de l' Espai (ICE CSIC), Campus Uab, Bellaterra, Spain ; Institut d' Estudis Espacials de Catalunya (IEEC), Barcelona, Spain
Ricker, G.; Kavli Institute for Astrophysics and Space Research, Massachusetts Institute of Technology, Cambridge, United States ; Department of Physics, Massachusetts Institute of Technology, Cambridge, United States
Santos, N.C.; Instituto de Astrofisica e Ciencias Do Espaco, Universidade Do Porto, Caup, Porto, Portugal ; Departamento de Fisica e Astronomia, Faculdade de Ciencias, Universidade Do Porto, Porto, Portugal
Scandariato, G.; Inaf, Osservatorio Astrofisico di Catania, Catania, Italy
Seager, S.; Kavli Institute for Astrophysics and Space Research, Massachusetts Institute of Technology, Cambridge, United States ; Department of Physics, Massachusetts Institute of Technology, Cambridge, United States ; Department of Earth Atmospheric and Planetary Science, Massachusetts Institute of Technology, Cambridge, United States ; Department of Aeronautics and Astronautics, Mit, Cambridge, United States
Ségransan, D.; Observatoire Astronomique de l' Université de Genève, Versoix, Switzerland
Simon, A.E.; Physikalisches Institut, University of Bern, Bern, Switzerland
Smith, A.M.S.; Institute of Planetary Research, German Aerospace Center (DLR), Berlin, Germany
Sousa, S.G.; Instituto de Astrofisica e Ciencias Do Espaco, Universidade Do Porto, Caup, Porto, Portugal
Steller, M.; Space Research Institute, Austrian Academy of Sciences, Graz, Austria
Szabó, Gy. M.; Elte Eötvös Loránd University, Gothard Astrophysical Observatory, Szombathely, Hungary ; MTA-ELTE Exoplanet Research Group, Szombathely, Hungary
Thomas, N.; Physikalisches Institut, University of Bern, Bern, Switzerland
Udry, S.; Observatoire Astronomique de l' Université de Genève, Versoix, Switzerland
Vanderspek, R.; Kavli Institute for Astrophysics and Space Research, Massachusetts Institute of Technology, Cambridge, United States
Venturini, J.; Observatoire Astronomique de l' Université de Genève, Versoix, Switzerland
Viotto, V.; Inaf, Osservatorio Astronomico di Padova, Padova, Italy
Walton, N.A.; Institute of Astronomy, University of Cambridge, Cambridge, United Kingdom
Winn, J.N.; Department of Astrophysical Sciences, Princeton University, Princeton, United States
CHEOPS is an ESA mission in partnership with Switzerland with important contributions to the payload and the ground segment from Austria, Belgium, France, Germany, Hungary, Italy, Portugal, Spain, Sweden, and the United Kingdom. The CHEOPS Consortium would like to gratefully acknowledge the support received by all the agencies, offices, universities, and industries involved. Their flexibility and willingness to explore new approaches were essential to the success of this mission. The Belgian participation to CHEOPS has been supported by the Belgian Federal Science Policy Office (BELSPO) in the framework of the PRODEX Program, and by the University of Liège through an ARC grant for Concerted Research Actions financed by the Wallonia-Brussels Federation. L.D. is an F.R.S.-FNRS Postdoctoral Researcher. This work has been carried out within the framework of the NCCR PlanetS supported by the Swiss National Science Foundation under grants 51NF40_182901 and 51NF40_205606. A.Br. was supported by the SNSA. M.G. is an F.R.S.-FNRS Senior Research Associate. A.C.C. acknowledges support from STFC consolidated grant numbers ST/R000824/1 and ST/V000861/1, and UKSA grant number ST/R003203/1. This work was also partially supported by a grant from the Simons Foundation (PI Queloz, grant number 327127). V.V.G. is an F.R.S.-FNRS Research Associate. A.C.C. and T.G.W. acknowledge support from STFC consolidated grant numbers ST/R000824/1 and ST/V000861/1, and UKSA grant number ST/R003203/1. Y.A. and M.J.H. acknowledge the support of the Swiss National Fund under grant 200020_172746. We acknowledge support from the Spanish Ministry of Science and Innovation and the European Regional Development Fund through grants ESP2016-80435-C2-1-R, ESP2016-80435-C2-2-R, PGC2018-098153- B-C33, PGC2018-098153-B-C31, ESP2017-87676-C5-1-R, MDM-2017-0737 Unidad de Excelencia Maria de Maeztu-Centro de Astrobiología (INTA- CSIC), as well as the support of the Generalitat de Catalunya/CERCA programme. The MOC activities have been supported by the ESA contract No. 4000124370. S.C.C.B. acknowledges support from FCT through FCT contracts nr. IF/01312/2014/CP1215/CT0004. X.B., S.C., D.G., M.F. and J.L. acknowledge their role as ESA-appointed CHEOPS science team members. L.Bo., G.Br., V.Na., I.Pa., G.Pi., R.Ra., G.Sc., V.Si., and T.Zi. acknowledge support from CHEOPS ASI-INAF agreement n. 2019-29-HH.0. P.E.C. is funded by the Austrian Science Fund (FWF) Erwin Schroedinger Fellowship, program J4595-N. This project was supported by the CNES. This work was supported by FCT – Fundação para a Ciência e a Tecnologia through national funds and by FEDER through COMPETE2020 – Programa Operacional Competitividade e Internacionalizacão by these grants: UID/FIS/04434/2019, UIDB/04434/2020, UIDP/04434/2020, PTDC/FIS-AST/32113/2017 and POCI-01-0145-FEDER- 032113, PTDC/FIS-AST/28953/2017 and POCI-01-0145-FEDER-028953, PTDC/FIS-AST/28987/2017 and POCI-01-0145-FEDER-028987. O.D.S.D. is supported in the form of work contract (DL 57/2016/CP1364/CT0004) funded by national funds through FCT. B.-O.D. acknowledges support from the Swiss State Secretariat for Education, Research and Innovation (SERI) under contract number MB22.00046. This project has received funding from the European Research Council (ERC) under the European Union’s Horizon 2020 research and innovation programme (project F OUR A CES , grant agreement No 724427). It has also been carried out in the frame of the National Centre for Competence in Research PlanetS supported by the Swiss National Science Foundation (SNSF). D.E. acknowledges financial support from the Swiss National Science Foundation for project 200021_200726. M.F. gratefully acknowledges the support of the Swedish National Space Agency (DNR 65/19, 174/18). D.G. gratefully acknowledges financial support from the CRT foundation under Grant No. 2018.2323 ‘Gaseous or rocky? Unveiling the nature of small worlds’. S.H. gratefully acknowledges CNES funding through the grant 837319. K.G.I. is the ESA CHEOPS Project Scientist and is responsible for the ESA CHEOPS Guest Observers Programme. She does not participate in, or contribute to, the definition of the Guaranteed Time Programme of the CHEOPS mission through which observations described in this paper have been taken, nor to any aspect of target selection for the programme. This work was granted access to the HPC resources of MesoPSL financed by the Région Île de France and the project Equip@Meso (reference ANR-10-EQPX-29-01) of the programme Investissements d’Avenir supervised by the Agence Nationale pour la Recherche. M.L. acknowledges support of the Swiss National Science Foundation under grant number PCEFP2_194576. R.L. acknowledges funding from University of La Laguna through the Margarita Salas Fellowship from the Spanish Ministry of Universities ref. UNI/551/2021-May 26, and under the EU Next Generation funds. P.M. acknowledges support from STFC research grant number ST/M001040/1. I.Ri. acknowledges support from the Spanish Ministry of Science and Innovation and the European Regional Development Fund through grant PGC2018-098153-B-C33, as well as the support of the Generalitat de Catalunya/CERCA programme. S.G.S. acknowledges support from FCT through FCT contract nr. CEECIND/00826/2018 and POPH/FSE (EC). Gy.M.Sz. acknowledges the support of the Hungarian National Research, Development and Innovation Office (NKFIH) grant K-125015, a PRODEX Experiment Agreement No. 4000137122, the Lendület LP2018-7/2021 grant of the Hungarian Academy of Science and the support of the city of Szombathely. N.A.W. acknowledges UKSA grant ST/R004838/1. Funding for the TESS mission is provided by the NASA’s Science Mission Directorate. We acknowledge the use of public TESS data from pipelines at the TESS Science Office and at the TESS Science Processing Operations Center. Resources supporting this work were provided by the NASA High-End Computing (HEC) Program through the NASA Advanced Supercomputing (NAS) Division at Ames Research Center for the production of the SPOC data products. This paper includes data collected by the TESS mission that are publicly available from the Mikulski Archive for Space Telescopes (MAST). We thank the anonymous referee for taking the time to review our work and for her/his valuable suggestions.
Commentary :
20 pages, 5 figures, 9 tables. Accepted for publication in A&A
