Methods: observational; Planets and satellites: fundamental parameters; Techniques: photometric; Echelle spectrograph; Exo-planets; Host-stars; Methods:observational; Orbital periods; Planetary system; Radial velocity; Satellite observations; Astronomy and Astrophysics; Space and Planetary Science; astro-ph.EP
Abstract :
[en] Context. Multi-planet systems are important sources of information regarding the evolution of planets. However, the long-period planets in these systems often escape detection. These objects in particular may retain more of their primordial characteristics compared to close-in counterparts because of their increased distance from the host star. HD 22946 is a bright (G = 8.13 mag) late F-type star around which three transiting planets were identified via Transiting Exoplanet Survey Satellite (TESS) photometry, but the true orbital period of the outermost planet d was unknown until now. Aims. We aim to use the Characterising Exoplanet Satellite (CHEOPS) space telescope to uncover the true orbital period of HD 22946d and to refine the orbital and planetary properties of the system, especially the radii of the planets. Methods. We used the available TESS photometry of HD 22946 and observed several transits of the planets b, c, and d using CHEOPS. We identified two transits of planet d in the TESS photometry, calculated the most probable period aliases based on these data, and then scheduled CHEOPS observations. The photometric data were supplemented with ESPRESSO (Echelle SPectrograph for Rocky Exoplanets and Stable Spectroscopic Observations) radial velocity data. Finally, a combined model was fitted to the entire dataset in order to obtain final planetary and system parameters. Results. Based on the combined TESS and CHEOPS observations, we successfully determined the true orbital period of the planet d to be 47.42489 ± 0.00011 days, and derived precise radii of the planets in the system, namely 1.362 ± 0.040 R, 2.328 ± 0.039 R, and 2.607 ± 0.060 R for planets b, c, and d, respectively. Due to the low number of radial velocities, we were only able to determine 3σ upper limits for these respective planet masses, which are 13.71 M, 9.72 M, and 26.57 M. We estimated that another 48 ESPRESSO radial velocities are needed to measure the predicted masses of all planets in HD 22946. We also derived stellar parameters for the host star. Conclusions. Planet c around HD 22946 appears to be a promising target for future atmospheric characterisation via transmission spectroscopy. We can also conclude that planet d, as a warm sub-Neptune, is very interesting because there are only a few similar confirmed exoplanets to date. Such objects are worth investigating in the near future, for example in terms of their composition and internal structure.
Disciplines :
Space science, astronomy & astrophysics
Author, co-author :
Garai, Z. ; MTA-ELTE Exoplanet Research Group, Szombathely, Hungary ; Elte Gothard Astrophysical Observatory, Szombathely, Hungary ; Astronomical Institute, Slovak Academy of Sciences, Tatranská Lomnica, Slovakia
Osborn, H.P.; Physikalisches Institut, University of Bern, Bern, Switzerland ; Department of Physics and Kavli Institute for Astrophysics and Space Research, Massachusetts Institute of Technology, Cambridge, United States
Gandolfi, D. ; Dipartimento di Fisica, Universita Degli Studi di Torino, Torino, Italy
Brandeker, A.; Department of Astronomy, Stockholm University, AlbaNova University Center, Stockholm, Sweden
Sousa, S.G. ; Instituto de Astrofísica e Ciencias Do Espaco, Universidade Do Porto, Caup, Porto, Portugal
Lendl, M. ; Observatoire Astronomique de 1'Université de Genève, Versoix, Switzerland
Bekkelien, A. ; Observatoire Astronomique de 1'Université de Genève, Versoix, Switzerland
Broeg, C. ; Physikalisches Institut, University of Bern, Bern, Switzerland ; Center for Space and Habitability, University of Bern, Bern, Switzerland
Cameron, A. Collier; 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
Hooton, M.J. ; Physikalisches Institut, University of Bern, Bern, Switzerland ; Astrophysics Group, Cavendish Laboratory, University of Cambridge, Cambridge, United Kingdom
Alibert, Y. ; Physikalisches Institut, University of Bern, Bern, Switzerland
Delrez, Laetitia ; Université de Liège - ULiège > Département d'astrophysique, géophysique et océanographie (AGO) > Exoplanets in Transit: Identification and Characterization
Fossati, L. ; Space Research Institute, Austrian Academy of Sciences, Graz, Austria
Salmon, S.; Observatoire Astronomique de 1'Université de Genève, Versoix, Switzerland
Wilson, T.G. ; Centre for Exoplanet Science, Supa School of Physics and Astronomy, University of St Andrews, St Andrews, United Kingdom
Bonfanti, A. ; Space Research Institute, Austrian Academy of Sciences, Graz, Austria
Tuson, A. ; Astrophysics Group, Cavendish Laboratory, University of Cambridge, Cambridge, United Kingdom
Ulmer-Moll, S. ; Physikalisches Institut, University of Bern, Bern, Switzerland ; Observatoire Astronomique de 1'Université de Genève, Versoix, Switzerland
Serrano, L.M.; Dipartimento di Fisica, Universita Degli Studi di Torino, Torino, Italy
Borsato, L. ; Inaf, Osservatorio Astronomico di Padova, Padova, Italy
Alonso, R. ; Instituto de Astrofísica de Canarias, La Laguna, Spain ; Departamento de Astrofísica, Universidad de la Laguna, La Laguna, Spain
Anglada, G.; Institut d'Estudis Espacials de Catalunya (IEEC), Barcelona, Spain ; Institut de Ciencies de l'Espai (ICE, CSIC), Bellaterra, Spain
Asquier, J.; European Space Agency (ESA), European Space Research and Technology Centre (ESTEC), Noordwijk, Netherlands
Barrado Y Navascues, D. ; Depto. de Astrofísica, Centro de Astrobiologia (CSIC-INTA), Madrid, Spain
Barros, S.C.C.; Instituto de Astrofísica e Ciencias Do Espaco, Universidade Do Porto, Caup, Porto, Portugal ; Departamento de Fisica e Astronomia, Faculdade de Ciencias, Universidade Do Porto, Porto, Portugal
Bárczy, T. ; Admatis, Miskolc, Hungary
Baumjohann, W. ; Space Research Institute, Austrian Academy of Sciences, Graz, Austria
Beck, M.; Observatoire Astronomique de 1'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 1'Université de Genève, Versoix, Switzerland
Biondi, F.; Inaf, Osservatorio Astronomico di Padova, Padova, Italy ; Max Planck Institute for Extraterrestrial Physics, Garching bei München, Germany
Bonfils, X.; Université Grenoble Alpes, Cnrs, Ipag, Grenoble, France
Buder, M.; Institute of Planetary Research, 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 Astrofísico di Torino, Pino Torinese, Italy
Davies, M.B.; Centre for Mathematical Sciences, Lund University, Lund, Sweden
Deleuil, M. ; Aix-Marseille Univ., Cnrs, Cnes, Lam, Marseille, France
Demangeon, O.D.S. ; Université Grenoble Alpes, Cnrs, Ipag, Grenoble, France ; Departamento de Fisica e Astronomia, Faculdade de Ciencias, Universidade Do Porto, Porto, Portugal
Demory, B.-O. ; Center for Space and Habitability, University of Bern, Bern, Switzerland
Ehrenreich, D.; Observatoire Astronomique de 1'Université de Genève, Versoix, Switzerland
Erikson, A.; Institute of Planetary Research, German Aerospace Center (DLR), Berlin, Germany
Van Eylen, V. ; Department of Space and Climate Physics, Mullard Space Science Laboratory, United Kingdom
Fortier, A.; Physikalisches Institut, University of Bern, Bern, Switzerland ; Center for Space and Habitability, University of Bern, Bern, Switzerland
Fridlund, M.; Leiden Observatory, University of Leiden, Leiden, Netherlands ; Department of Space, Earth and Environment, Chalmers University of Technology, Onsala Space Observatory, Onsala, Sweden
Gillon, Michaël ; Université de Liège - ULiège > Département d'astrophysique, géophysique et océanographie (AGO)
Van Grootel, Valérie ; Université de Liège - ULiège > Département d'astrophysique, géophysique et océanographie (AGO) > Astrophysique stellaire théorique et astérosismologie
Güdel, M.; Department of Astrophysics, University of Vienna, Vienna, Austria
Günther, M.N.; European Space Agency (ESA), European Space Research and Technology Centre (ESTEC), Noordwijk, Netherlands
Hoyer, S.; Aix-Marseille Univ., Cnrs, Cnes, Lam, Marseille, France
Isaak, K.G.; European Space Agency (ESA), European Space Research and Technology Centre (ESTEC), Noordwijk, Netherlands
Kiss, L.L. ; Konkoly Observatory, Research Centre for Astronomy and Earth Sciences, Budapest, Hungary
Laskar, J.; Imcce, UMR8028 Cnrs, Observatoire de Paris, Psl Univ., Paris, France
Des Etangs, A. Lecavelier ; Institut d'Astrophysique de Paris, UMR7095 Cnrs, Université Pierre-et-Marie-Curie, Paris, France
Lovis, C. ; Observatoire Astronomique de 1'Université de Genève, Versoix, Switzerland
Luntzer, A. ; Department of Astrophysics, University of Vienna, Vienna, Austria
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
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 Astrofísico di Catania, Catania, Italy
Pallé, E. ; Instituto de Astrofísica de Canarias, La Laguna, Spain ; Departamento de Astrofísica, Universidad de la Laguna, La Laguna, Spain
Peter, G.; Institute of Planetary Research, 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
Queloz, D. ; Astrophysics Group, Cavendish Laboratory, University of Cambridge, Cambridge, United Kingdom ; Observatoire Astronomique de 1'Université de Genève, Versoix, Switzerland
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.; European Space Agency (ESA), European Space Research and Technology Centre (ESTEC), Noordwijk, Netherlands
Rauer, H.; Institute of Planetary Research, German Aerospace Center (DLR), Berlin, Germany ; Center for Astronomy and Astrophysics, Technical University Berlin, Berlin, Germany
Ribas, I. ; Institut d'Estudis Espacials de Catalunya (IEEC), Barcelona, Spain ; Institut de Ciencies de l'Espai (ICE, CSIC), Bellaterra, Spain
Santos, N.C. ; Instituto de Astrofísica 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 Astrofísico di Catania, Catania, Italy
Ségransan, D.; Observatoire Astronomique de 1'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
Steller, M.; Space Research Institute, Austrian Academy of Sciences, Graz, Austria
Szabó, Gy. M.; MTA-ELTE Exoplanet Research Group, Szombathely, Hungary ; Elte Gothard Astrophysical Observatory, Szombathely, Hungary
Thomas, N.; Physikalisches Institut, University of Bern, Bern, Switzerland
Udry, S. ; Observatoire Astronomique de 1'Université de Genève, Versoix, Switzerland
Venturini, J.; Observatoire Astronomique de 1'Université de Genève, Versoix, Switzerland
Walton, N. ; Institute of Astronomy, University of Cambridge, Cambridge, United Kingdom
We thank the anonymous reviewer for the helpful comments and suggestions. 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. This paper includes data collected with the TESS mission, obtained from the MAST data archive at the Space Telescope Science Institute (STScI). Funding for the TESS mission is provided by the NASA Explorer Program. STScI is operated by the Association of Universities for Research in Astronomy, Inc., under NASA contract NAS 5-26555. This research has made use of the Exoplanet Follow-up Observation Program (ExoFOP; DOI: 10.26134/ExoFOP5) website, which is operated by the California Institute of Technology, under contract with the National Aeronautics and Space Administration under the Exoplanet Exploration Program. This work has made use of data from the European Space Agency (ESA) mission Gaia ( https://www.cosmos.esa.int/gaia ), processed by the Gaia Data Processing and Analysis Consortium (DPAC, https://www.cosmos.esa.int/web/gaia/dpac/consortium ). Funding for the DPAC has been provided by national institutions, in particular the institutions participating in the Gaia Multilateral Agreement. Z.G. acknowledges the support of the Hungarian National Research, Development and Innovation Office (NKFIH) grant K-125015, the PRODEX Experiment Agreement No. 4000137122 between the ELTE Eötvös Loránd University and the European Space Agency (ESA-D/SCI-LE-2021-0025), the VEGA grant of the Slovak Academy of Sciences No. 2/0031/22, the Slovak Research and Development Agency contract No. APVV-20-0148, and the support of the city of Szombathely. Gy.M.Sz. acknowledges the support of the Hungarian National Research, Development and Innovation Office (NKFIH) grant K-125015, a PRODEX Institute Agreement between the ELTE Eötvös Loránd University and the European Space Agency (ESA-D/SCI-LE-2021-0025), the Lendület LP2018-7/2021 grant of the Hungarian Academy of Science and the support of the city of Szombathely. A.Br. was supported by the SNSA. A.C.C. acknowledges support from STFC consolidated grant numbers ST/R000824/1 and ST/V000861/1, and UKSA grant number ST/R003203/1. 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 FOUR ACES; 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. D.G. gratefully acknowledges financial support from the CRT foundation under Grant No. 2018.2323 “Gaseousor rocky? Unveiling the nature of small worlds”. This work was also partially supported by a grant from the Simons Foundation (PI Queloz, grant number 327127). 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. I.R.I. 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. 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. K.G.I. and M.N.G. are the ESA CHEOPS Project Scientists and are responsible for the ESA CHEOPS Guest Observers Programme. They do 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. 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. L.M.S. gratefully acknowledges financial support from the CRT foundation under Grant No. 2018.2323 “Gaseous or rocky? Unveiling the nature of small worlds”. This project was supported by the CNES. M.F. and C.M.P. gratefully acknowledge the support of the Swedish National Space Agency (DNR 65/19, 174/18). M.G. is an F.R.S.-FNRS Senior Research Associate. M.L. acknowledges support of the Swiss National Science Foundation under grant number PCEFP2_194576. N.A.W. acknowledges UKSA grant ST/R004838/1. 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 & POCI-01-0145-FEDER-032113, PTDC/FIS-AST/28953/2017 & POCI-01-0145-FEDER-028953, PTDC/FIS-AST/28987/2017 & 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. P.M. acknowledges support from STFC research grant number ST/M001040/1. 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.H. gratefully acknowledges CNES funding through the grant 837319. S.C.C.B. acknowledges support from FCT through FCT contracts nr. IF/01312/2014/CP1215/CT0004. S.G.S. acknowledges support from FCT through FCT contract no. CEECIND/00826/2018 and POPH/FSE (EC). A.C.C. and T.W. acknowledge support from STFC consolidated grant numbers ST/R000824/1 and ST/V000861/1, and UKSA grant number ST/R003203/1. V.V.G. is an F.R.S-FNRS Research Associate. X.B., S.C., D.G., M.F. and J.L. acknowledge their role as ESA-appointed CHEOPS science team members. Y.A. and M.J.H. acknowledge the support of the Swiss National Fund under grant 200020_172746. L.Bo., V.Na., I.Pa., G.Pi., R.Ra. and G.Sc. acknowledge support from CHEOPS ASI-INAF agreement n. 2019-29-HH.0. NCS acknowledges support from the European Research Council through the grant agreement 101052347 (FIERCE). 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 Internacionalização by these grants: UIDB/04434/2020; UIDP/04434/2020. A.T. thanks the Science and Technology Facilities Council (STFC) for a PhD studentship. P.E.C. is funded by the Austrian Science Fund (FWF) Erwin Schroedinger Fellowship, program J4595-N.
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