Characterising TOI-732 b and c

Author(s): A. Bonfanti, M. Brady, T. G. Wilson, J. Venturini, J. A. Egger, A. Brandeker, S. G. Sousa, M. Lendl, A. E. Simon, D. Queloz, G. Olofsson, V. Adibekyan, Y. Alibert, L. Fossati, M. J. Hooton, D. Kubyshkina, R. Luque, F. Murgas, A. J. Mustill, N. C. Santos, V. Van Grootel, R. Alonso, J. Asquier, T. Bandy, T. Bárczy, D. Barrado Navascues, S. C.C. Barros, W. Baumjohann, J. Bean, M. Beck, T. Beck, W. Benz, M. Bergomi, N. Billot, L. Borsato, C. Broeg, A. Collier Cameron, Sz Csizmadia, P. E. Cubillos, M. B. Davies, M. Deleuil, A. Deline, L. Delrez, O. D.S. Demangeon, B. O. Demory, D. Ehrenreich, A. Erikson, A. Fortier, M. Fridlund, D. Gandolfi, M. Gillon, M. Güdel, M. N. Günther, A. Heitzmann, Ch Helling, S. Hoyer, K. G. Isaak, D. Kasper, L. L. Kiss, K. W.F. Lam, J. Laskar, A. Lecavelier des Etangs, D. Magrin, P. F.L. Maxted, C. Mordasini, V. Nascimbeni, R. Ottensamer, I. Pagano, E. Pallé, G. Peter, G. Piotto, D. Pollacco, R. Ragazzoni, N. Rando, H. Rauer, I. Ribas, G. Scandariato, D. Ségransan, A. Seifahrt, A. M.S. Smith, M. Stalport, G. Stefánsson, M. Steinberger, J. Stürmer, Gy M. Szabó, N. Thomas, S. Udry, E. Villaver, N. A. Walton, K. Westerdorff, T. Zingales
Abstract: Context. TOI-732 is an M dwarf hosting two transiting planets that are located on the two opposite sides of the radius valley. Inferring a reliable demographics for this type of systems is key to understanding their formation and evolution mechanisms. Aims. By doubling the number of available space-based observations and increasing the number of radial velocity (RV) measurements, we aim at refining the parameters of TOI-732 b and c. We also use the results to study the slope of the radius valley and the density valley for a well-characterised sample of M-dwarf exoplanets. Methods. We performed a global Markov chain Monte Carlo analysis by jointly modelling ground-based light curves and CHEOPS and TESS observations, along with RV time series both taken from the literature and obtained with the MAROON-X spectrograph. The slopes of the M-dwarf valleys were quantified via a support vector machine (SVM) procedure. Results. TOI-732 b is an ultrashort-period planet (P = 0.76837931₋⁺₀⁰_00000042^00000039 days) with a radius R_b = 1.325⁺₋⁰₀⁰⁵⁷₀₅₈ R_☉, a mass M_b = 2.46 ± 0.19 M_☉, and thus a mean density ρ_b = 5.8⁺₋¹₀⁰₈ g cm⁻³, while the outer planet at P = 12.252284 ± 0.000013 days has R_c = 2.39⁺₋⁰₀¹⁰₁₁ R_☉, M_c = 8.04⁺₋⁰₀⁵⁰₄₈ M_☉, and thus ρ_c = 3.24⁺₋⁰₀⁵⁵₄₃ g cm⁻³. Even with respect to the most recently reported values, this work yields uncertainties on the transit depths and on the RV semi-amplitudes that are smaller up to a factor of ∼1.6 and ∼2.4 for TOI-732 b and c, respectively. Our calculations for the interior structure and the location of the planets in the mass-radius diagram lead us to classify TOI-732 b as a super-Earth and TOI-732 c as a mini-Neptune. Following the SVM approach, we quantified d log R_p,valley/d log P = −0.065⁺₋⁰₀⁰²⁴₀₁₃, which is flatter than for Sun-like stars. In line with former analyses, we note that the radius valley for M-dwarf planets is more densely populated, and we further quantify the slope of the density valley as d log ρ̂_valley/d log P = −0.02⁺₋⁰₀¹²₀₄. Conclusions. Compared to FGK stars, the weaker dependence of the position of the radius valley on the orbital period might indicate that the formation shapes the radius valley around M dwarfs more strongly than the evolution mechanisms.
Organisation(s): Department of Astrophysics
External organisation(s): Österreichische Akademie der Wissenschaften (ÖAW), University of Chicago, University of Warwick, Université de Genève, Universität Bern, Stockholm University, Universidade do Porto, Eidgenössische Technische Hochschule Zürich, University of Cambridge, Institute of Astrophysics of the Canary Islands, University of La Laguna, Lund Observatory, Université de Liège, Science and Operations Department - Science Division (SCI-SC), Admatis Ltd., European Space Astronomy Centre (ESA), Osservatorio Astronomico, University of St. Andrews, Deutsches Zentrum für Luft- und Raumfahrt e.V. (DLR), INAF-Osservatorio Astrofisico di Torino, Lund University, Aix-Marseille Université, Leiden University, Chalmers University of Technology, University of Turin, Technische Universität Graz, Eötvös Loránd Research Network, Eötvös Loránd University Budapest, Université de recherche Paris Sciences et Lettres, Université Paris VI - Pierre-et-Marie-Curie, Keele University, INAF-Osservatorio Astrofisico di Catania, University of Padova, Technische Universität Berlin, Freie Universität Berlin (FU), Spanish National Research Council (CSIC), Institute of Space Studies of Catalonia (IEEC), Princeton University, Landessternwarte Königstuhl (LSW), HUN-REN Hungarian Research Network
Journal: Astronomy and Astrophysics
Volume: 682
No. of pages: 28
ISSN: 0004-6361
DOI: https://doi.org/10.1051/0004-6361/202348180
Publication date: 02-2024
Peer reviewed: Yes
Austrian Fields of Science 2012: 103003 Astronomy, 103004 Astrophysics
Keywords
ASJC Scopus subject areas: Astronomy and Astrophysics, Space and Planetary Science
Portal url: https://ucrisportal.univie.ac.at/en/publications/32309290-7ca8-4285-a526-c4e566bf5992

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