planets and satellites: detection; planets and satellites: fundamental parameters; stars: individual: HD 224018; techniques: photometric; techniques: radial velocities; Follow up; Jupiters; Neptune; Planets and satellites: detections; Planets and satellites: fundamental parameters; Radial velocity; Star: individual: HD 224018; Stars: individual: proxima Centauri; Techniques: photometric; Techniques: radial velocities; Astronomy and Astrophysics; Space and Planetary Science; astro-ph.EP
Abstract :
[en] Context. Exoplanetary systems show a large diversity of architectures and planet types. Among the increasing number of exodemographics studies, those exploring correlations between the presence of close-in small planets and cold Jupiters are the object of particular attention. Aims. In 2016, Kepler/K2 detected a system of two sub-Neptunes transiting the star HD 224018, one of them showing a mono-transit event. In 2017, we began a spectroscopic follow-up with HARPS-N to measure the dynamical masses of the planets using radial velocities, and collected additional transit observations using CHEOPS. Methods. We measured the fundamental physical parameters of the host star, which is an ‘old Sun’ analogue. We analysed radial velocities and photometric time series, also including data by TESS, to provide precise ephemerides, radii, masses, and bulk densities of the two planets, and possibly modelling their internal structure and composition. Results. The system turned out to be more crowded than was shown by Kepler/K2. Radial velocities revealed the presence of two additional bodies: a candidate cold companion on an eccentric orbit with a minimum mass nearly half that of Jupiter (eccentricity 0.60−0.08+0.07; semi-major axis 8.6−1.6+1.5 au), and an innermost super-Earth (orbital period 10.6413±0.0028 d; mass 4.1±0.8 M⊕) for which we discovered previously undetected transit events in Kepler/K2 photometry. TESS data revealed a second transit of one of the two companions originally observed by Kepler/K2. This allowed us to constrain its orbital period to a grid of values, the most likely being ~138 days, which would imply a mass less than 9 M⊕ at a 3σ significance level. Given the level of precision of our measurements, we were able to constrain the internal structure and composition of the second-most distant planet from the host star, a warm sub-Neptune with a bulk density of 3.9±0.5 g cm−3. Conclusions. HD 224018 hosts three close-in transiting planets in the super-Earth-to-sub-Neptune regime, and a candidate cold and eccentric massive companion. Additional follow-up is needed to better characterise the physical properties of the planets and their architecture, and to study the evolutionary history of the system.
Research Center/Unit :
STAR - Space sciences, Technologies and Astrophysics Research - ULiège Astrobiology - ULiège
Disciplines :
Space science, astronomy & astrophysics
Author, co-author :
Damasso, M. ; INAF, Osservatorio Astrofisico di Torino, Pino Torinese, Italy
Naponiello, L. ; INAF, Osservatorio Astrofisico di Torino, Pino Torinese, Italy
Anna John, A.; School of Physics & Astronomy, University of Birmingham, Birmingham, United Kingdom ; SUPA, School of Physics & Astronomy, University of St Andrews, St Andrews, United Kingdom ; Centre for Exoplanet Science, University of St Andrews, St Andrews, United Kingdom
Egger, J.A. ; Space Research and Planetary Sciences, Physics Institute, University of Bern, Bern, Switzerland
Cretignier, M. ; Sub-department of Astrophysics, University of Oxford, Oxford, United Kingdom
Mortier, A. ; School of Physics & Astronomy, University of Birmingham, Birmingham, United Kingdom
Collier Cameron, A. ; SUPA, School of Physics & Astronomy, University of St Andrews, St Andrews, United Kingdom ; Centre for Exoplanet Science, University of St Andrews, St Andrews, United Kingdom
Dumusque, X. ; Observatoire Astronomique de l’Université de Genève, Versoix, Switzerland
Wilson, T. ; Department of Physics, University of Warwick, Coventry, United Kingdom
Buchhave, L. ; DTU Space, Technical University of Denmark, Kgs. Lyngby, Denmark
Nicholson, B. ; University of Southern Queensland, Centre for Astrophysics, Toowoomba, Australia
Stalport, Manu ; Université de Liège - ULiège > Unités de recherche interfacultaires > Space sciences, Technologies and Astrophysics Research (STAR)
Ghedina, A. ; Fundación Galileo Galilei, INAF, Breña Baja, Spain
Latham, D.W. ; Center for Astrophysics I Harvard & Smithsonian, Cambridge, United States
Livingston, J. ; Astrobiology Center, Tokyo, Japan ; National Astronomical Observatory of Japan, Tokyo, Japan ; Department of Astronomy, The Graduate University for Advanced Studies (SOKENDAI), Tokyo, Japan
Malavolta, L. ; INAF, Osservatorio Astronomico di Padova, Padova, Italy ; Dipartimento di Fisica e Astronomia ‘Galileo Galilei’, Università degli Studi di Padova, Padova, Italy
Sozzetti, A. ; INAF, Osservatorio Astrofisico di Torino, Pino Torinese, Italy
Jenkins, J.M. ; NASA Ames Research Center, Moffett Field, United States
Mantovan, G. ; INAF, Osservatorio Astronomico di Padova, Padova, Italy ; Dipartimento di Fisica e Astronomia ‘Galileo Galilei’, Università degli Studi di Padova, Padova, Italy
Palethorpe, L. ; SUPA, Institute for Astronomy, University of Edinburgh, Edinburgh, United Kingdom ; Centre for Exoplanet Science, University of Edinburgh, Edinburgh, United Kingdom
Tronsgaard, R. ; DTU Space, National Space Institute, Technical University of Denmark, Kgs. Lyngby, Denmark ; Cavendish Laboratory, University of Cambridge, Cambridge, United Kingdom
Udry, S. ; Astronomy Department of the University of Geneva, Versoix, Switzerland
Watson, C.A.; Astrophysics Research Centre, School of Mathematics and Physics, Queen’s University Belfast, Belfast, United Kingdom
The HARPS-N project was funded by the Prodex Program of the Swiss Space Office (SSO), the Harvard University Origin ofLife Initiative (HUOLI), the Scottish Universities Physics Alliance (SUPA), the University of Geneva, the Smithsonian Astrophysical Observatory (SAO), the Italian National Astrophysical Institute (INAF), University of St. Andrews, Queen\u2019s University Belfast, and University of Edinburgh. We used 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. Kepler was competitively selected as the 10th Discovery mission. Funding for the Kepler/K2 missions were provided by NASA\u2019s Science Mission Directorate. CHEOPS is an ESA mission in partnership with Switzerland with contributions to the payload and the ground segment from Austria, Belgium, France, Germany, Hungary, Italy, Portugal, Spain, Sweden and the UK. We used data by the TESS mission. Funding for the TESS mission is provided by the NASA Explorer Program. We acknowledge the use of public TOI Release 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. We used The Data & Analysis Center for Exoplanets (DACE), which is a facility based at the University of Geneva (CH) dedicated to extrasolar planets data visualisation, exchange and analysis. DACE is a platform of the Swiss National Centre of Competence in Research (NCCR) PlanetS, federating the Swiss expertise in Exoplanet research. The DACE platform is available at https://dace.unige.ch . A.M. acknowledges funding from a UKRI Future Leader Fellowship, grant number MR/X033244/1 and a UK Science and Technology Facilities Council (STFC) small grant ST/Y002334/1. A.C.C acknowledges support from STFC consolidated grant number ST/V000861/1 and UKRI/ERC Synergy Grant EP/Z000181/1 (REVEAL). L.M. acknowledges support from the European Union- NextGenerationEU (PRIN MUR 2022 20229R43BH). R.T. acknowledges the Head of Department of Physics, the University of Cambridge, and the Carlsberg Foundation for supporting this research. C.A.W. would like to acknowledge support from the UK Science and Technology Facilities Council (STFC, grant number ST/X00094X/1). We acknowledge support from the INAF Large Grant 2023 \u2018EXODEMO\u2019, and from the Swiss National Science Foundation within the framework of the NCCR PlanetS under grants 51NF40_182901 and 51NF40_205606.The HARPS-N project was funded by the Prodex Program of the Swiss Space Office (SSO), the Harvard University Origin of Life Initiative (HUOLI), the Scottish Universities Physics Alliance (SUPA), the University of Geneva, the Smithsonian Astrophysical Observatory (SAO), the Italian National Astrophysical Institute (INAF), University of St. Andrews, Queen\u2019s University Belfast, and University of Edinburgh. We used data from the European Space Agency (ESA) mission Gaia (https://www.cosmos.esa.int/gaia), pro- cessed 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. Kepler was competitively selected as the 10th Discovery mission. Funding for the Kepler/K2 missions were provided by NASA\u2019s Science Mission Directorate. CHEOPS is an ESA mission in partnership with Switzerland with contributions to the payload and the ground segment from Austria, Belgium, France, Germany, Hungary, Italy, Portugal, Spain, Sweden and the UK. We used data by the TESS mission. Funding for the TESS mission is provided by the NASA Explorer Program. We acknowledge the use of public TOI Release 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 Com- puting (HEC) Program through the NASA Advanced Supercomputing (NAS) Division at Ames Research Center for the production of the SPOC data products. We used The Data & Analysis Center for Exoplanets (DACE), which is a facil- ity based at the University of Geneva (CH) dedicated to extrasolar planets data visualisation, exchange and analysis. DACE is a platform of the Swiss National Centre of Competence in Research (NCCR) PlanetS, federating the Swiss expertise in Exoplanet research. The DACE platform is available at https: //dace.unige.ch. A.M. acknowledges funding from a UKRI Future Leader Fellowship, grant number MR/X033244/1 and a UK Science and Technology Facilities Council (STFC) small grant ST/Y002334/1. A.C.C acknowledges sup- port from STFC consolidated grant number ST/V000861/1 and UKRI/ERC Synergy Grant EP/Z000181/1 (REVEAL). L.M. acknowledges support from the European Union- NextGenerationEU (PRIN MUR 2022 20229R43BH). R.T. acknowledges the Head of Department of Physics, the University of Cambridge, and the Carlsberg Foundation for supporting this research. C.A.W. would like to acknowledge support from the UK Science and Technology Facilities Council (STFC, grant number ST/X00094X/1). We acknowledge support from the INAF Large Grant 2023 \u2018EXODEMO\u2019, and from the Swiss National Science Founda- tion within the framework of the NCCR PlanetS under grants 51NF40_182901 and 51NF40_205606.
Commentary :
Accepted for publication on A&A (18 Aug 2025). Main text: 12 pages: Appendix: 4 pages
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