An ultra-short period super-Earth and sub-Neptune spanning the Radius Valley orbiting the kinematic thick disc star TOI-2345

ABSTRACT A crucial chemical link between stars and their orbiting exoplanets is thought to exist. If universal, this connection could affect the formation and evolution of all planets. Therefore, this potential vital link needs testing by characterizing exoplanets around chemically-diverse stars. We present the discovery of two planets orbiting the metal-poor, kinematic thick-disc K-dwarf TOI-2345. TOI-2345 b is a super-Earth with a period of 1.05 d and TOI-2345 c is a sub-Neptune with a period of 21 d. In addition to the target being observed in four TESS sectors, we obtained five CHEOPS visits and 26 radial velocities from HARPS. By conducting a joint analysis of all the data, we find TOI-2345 b to have a radius of $1.504\substack{+0.047 -0.044}$ R$_{\oplus }$ and a mass of $3.49\pm 0.85$ M$_{\oplus }$; and TOI-2345 c to have a radius of $2.451\substack{+0.045 -0.046}$ R$_{\oplus }$ and a mass of $7.27\substack{+2.27 -2.45}$ M$_{\oplus }$. To explore chemical links between these planets and their host star, we model their interior structures newly accounting for devolatized stellar abundances. TOI-2345 adds to the limited sample of well-characterized planetary systems around thick disc stars. This system challenges theories of formation and populations of planets around thick disc stars with its Ultra-Short Period super-Earth and the wide period distribution of these two planets spanning the radius valley.

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Journal
Monthly Notices of the Royal Astronomical Society
Published
2025-10-18
DOI
https://doi.org/10.1093/mnras/staf1806
Primary Topic
Stellar, planetary, and galactic studies
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article
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article

An ultra-short period super-Earth and sub-Neptune spanning the Radius Valley orbiting the kinematic thick disc star TOI-2345

M. Stalport, T. Bárczy, A. Bonfanti, Douglas A. Caldwell et al.
Monthly Notices of the Royal Astronomical Society
Stellar, planetary, and galactic studies
article

An ultra-short period super-Earth and sub-Neptune spanning the Radius Valley orbiting the kinematic thick disc star TOI-2345

M. Stalport, T. Bárczy, A. Bonfanti, Douglas A. Caldwell, A. Collier Cameron, N. Billot, Y. Alibert, A. M. S. Smith, J. Laskar, Jon M. Jenkins, W. Benz, Maximilian N. Günther, S. Sulis, M. Guêdel, L. Borsato, M. Gillon, H. G. Vivien, P. F. L. Maxted, Soléne Ulmer-Moll, Robert F. Goeke, V. Nascimbeni, Alexander J. Mustill, H. P. Osborn, M. Lendl, Jacopo Farinato, A. Erikson, Ε. Πάλλη, L. L. Kiss, D. Ségransan, D. Gandolfi, D. Queloz, D. Pollacco, A. C. M. Correia, A. E. Simon, G. Piotto, M. B. Davies, Gyula M. Szabó, F. Ratti, J. A. Egger, R. Alonso, G. Peter, Roberto Ragazzoni, J. Korth, A. Fortier, S. Wolf, A. Derekas, A. Castro-González, T. Keller, I. Ribas, K. W. F. Lam, C. M. Persson, Ch. Helling, C. Broeg, A. Heitzmann, Carl Ziegler, David Watanabe, Avi Shporer, H. Rauer, D. Barrado, N. A. Walton, A. Lecavelier des Étangs, Szilárd Csizmadia, W. Baumjohann, S. C. C. Barros, N. C. Santos, Patricio E. Cubillos, Daniel Kitzmann, J. Hasiba, Christoph Mordasini, Demetrio Magrin, K. Gazeas, J. Venturini, G. Olofsson, M. Fridlund, Brice-Olivier Demory, Adrien Leleu, L. Fossati, D. Ehrenreich, A. Deline, Billy Edwards, A. Brandeker, T. G. Wilson, S. Udry, B. Merín, Yoshi Nike Emilia Eschen, S. G. Sousa, Isabella Pagano, N. Rando, Magali Deleuil, Eva Villaver, D. Piazza, K. Isaak, O. D. S. Demangeon, Maximilian Buder, R. Ottensamer
article en

Abstract

ABSTRACT A crucial chemical link between stars and their orbiting exoplanets is thought to exist. If universal, this connection could affect the formation and evolution of all planets. Therefore, this potential vital link needs testing by characterizing exoplanets around chemically-diverse stars. We present the discovery of two planets orbiting the metal-poor, kinematic thick-disc K-dwarf TOI-2345. TOI-2345 b is a super-Earth with a period of 1.05 d and TOI-2345 c is a sub-Neptune with a period of 21 d. In addition to the target being observed in four TESS sectors, we obtained five CHEOPS visits and 26 radial velocities from HARPS. By conducting a joint analysis of all the data, we find TOI-2345 b to have a radius of $1.504\substack{+0.047 -0.044}$ R$_{\oplus }$ and a mass of $3.49\pm 0.85$ M$_{\oplus }$; and TOI-2345 c to have a radius of $2.451\substack{+0.045 -0.046}$ R$_{\oplus }$ and a mass of $7.27\substack{+2.27 -2.45}$ M$_{\oplus }$. To explore chemical links between these planets and their host star, we model their interior structures newly accounting for devolatized stellar abundances. TOI-2345 adds to the limited sample of well-characterized planetary systems around thick disc stars. This system challenges theories of formation and populations of planets around thick disc stars with its Ultra-Short Period super-Earth and the wide period distribution of these two planets spanning the radius valley.

Monthly Notices of the Royal Astronomical SocietyVol. 544(2)
Eötvös Loránd University (HU), University of Geneva (CH), University of Bern (CH), Leiden University (NL), Ames Research Center (US), Centre National de la Recherche Scientifique (FR), University of Vienna (AT), Planetary Science Institute (US), Bern University of Applied Sciences (CH), Institute of Space Sciences (ES), Austrian Academy of Sciences (AT), University of Padua (IT), Research Institute for Advanced Computer Science (US), University of Liège (BE), Universidad de La Laguna (ES), University of St Andrews (GB), Universidade do Porto (PT), Lund University (SE), National and Kapodistrian University of Athens (GR), Stephen F. Austin State University (US), University of Miskolc (HU), University of Applied Sciences Leiden (NL), Aix-Marseille Université (FR), University of Cambridge (GB), Université Paris Sciences et Lettres (FR), NASA Research Park (US), Institut d'Astrophysique de Paris (FR), European Space Agency (FR), Konkoly Observatory (HU), Deutsches Zentrum für Luft- und Raumfahrt e. V. (DLR) (DE), ETH Zurich (CH), University of Warwick (GB), Sorbonne Université (FR), Graz University of Technology (AT), Institute of Astrophysics and Space Sciences (PT), Institut d'Estudis Espacials de Catalunya (ES), European Space Astronomy Centre (ES), Laboratoire d’Astrophysique de Marseille (FR), Istituto Nazionale di Fisica Nucleare, Sezione di Torino (IT), Osservatorio Astrofisico di Torino (IT), Instituto de Física Teórica (ES), Institute of Astronomy (RU), Osservatorio Astrofisico di Catania (IT), FZU ‒ Institute of Physics of the Academy of Sciences of the Czech Republic (CZ), HUN-REN Research Centre for Astronomy and Earth Sciences (HU), Centro de Astrobiología (ES), Instituto de Astrofísica de Canarias (ES), AlbaNova (SE), Computational Physics (United States) (US), Astronomy and Space (AU), Szent Imre Egyetemi Oktatókórház (HU), Osservatorio Astronomico di Padova (IT), Leiden Observatory, European Space Research and Technology Centre (NL), Space Research Organisation Netherlands (NL), University of Turin (IT), Keele University (GB), Massachusetts Institute of Technology (US), Freie Universität Berlin (DE), University of Coimbra (PT), International Space Science Institute (CH)
National Science Foundation, National Aeronautics and Space Administration, California Institute of Technology, Fondazione CRT, Canadian Celiac Association, UK Space Agency, UK Research and Innovation, Centres de Recerca de Catalunya, European Space Agency, University of Warwick, European Commission, Deutsche Forschungsgemeinschaft, Agence Nationale de la Recherche, Schweizerischer Nationalfonds zur Förderung der Wissenschaftlichen Forschung, Swedish National Space Agency, Austrian Science Fund, Fonds De La Recherche Scientifique - FNRS, Generalitat de Catalunya, Centre National d’Etudes Spatiales, Institut Universitaire de France, Ministerio de Ciencia e Innovación, Nemzeti Kutatási Fejlesztési és Innovációs Hivatal, Instituto de Astrofísica de Canarias, Horizon 2020 Framework Programme, Science Mission Directorate, Science and Technology Facilities Council, Fundação para a Ciência e a Tecnologia, Staatssekretariat für Bildung, Forschung und Innovation, European Regional Development Fund, Agencia Estatal de Investigación, National Research, Development and Innovation Office
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