Revisiting TOI-4438 and TOI-442 planetary systems with new observations from SPIRou and TESS
Year: 2026
Type: article
Abstract: We present a comprehensive reanalysis of two star-planet systems: TOI-4438, an M3.5V star hosting a mini-Neptune in a 7.4-day orbit, and TOI-442, an M1V star with a 4-day period planet located within the hot Neptune desert. Both systems were originally identified as transiting planet candidates by the Transiting Exoplanet Survey Satellite (TESS) and subsequently validated through the radial velocity (RV) method. Our work incorporates new TESS transit data and high-resolution spectroscopy from the SPIRou near-infrared spectropolarimeter. We detected a persistent and relatively strong Zeeman signature in TOI-442, while TOI-4438 exhibits weaker and intermittent magnetic activity, and we inferred the stellar rotation periods of both stars from the variability of the longitudinal magnetic field. We jointly fit photometry and RV models for each system. For TOI-4438 b we combined archival CARMENES data with 81 SPIRou observations and five TESS sectors. This yielded a refined planetary mass of M p = 4.11 +0.40 −0.38 M ⊕ and a radius of R p = 2.40 +0.09 −0.10 R ⊕ , consistent with the previous estimate within 1.1 σ while improving by 53% the precision on the mass and 22% on the radius. For TOI-442 b, we added 29 SPIRou RV measurements to an extensive archival dataset, significantly extending the temporal baseline. Incorporating this with a new TESS sector, we tighten the constraints on the planetary mass to M p = 28.38 +0.77 −0.73 M ⊕ and radius to R p = 4.25 +0.10 −0.08 R ⊕ , which agrees with the previous values within 1.5 σ and improves the precisions by 46 and 67%, respectively. We found no clear signs of additional planets in the currently available RV data, although we detected a single-transit event in the TOI-4438 light curve. We compared various RV models and found that those accounting for stellar variability-induced signals yield improved constraints on the planetary parameters.
Source: Astronomy and Astrophysics
Authors: J. Serrano Bell, G. Hébrard, E. Martioli, R. F. Díaz, L. de Almeida, D. Lorenzo-Oliveira, A. Salmi, C. Dorn, M. Valatsou, A. Carmona, M. Ould-Elhkim, L. Arnold, É. Artigau, I. Boisse, X. Bonfils, C. Cadieux, Z. Chakir, N. J. Cook, X. Delfosse, J.-F. Donati, R. Doyon, N. Heidari, J. M. Jenkins, F. Kiefer, S. Lafrance, A. L’Heureux, C. Moutou, J. Morneau, X. Vandelac
Institutions: Consejo Nacional de Investigaciones Científicas y Técnicas, National University of General San Martín, Instituto Tecnológico de Buenos Aires (ITBA), Centre National de la Recherche Scientifique, Observatoire de Haute-Provence, Institut d'Astrophysique de Paris, Sorbonne Université, Laboratório Nacional de Astrofísica, Southern Astrophysical Research Telescope, NSF NOIRLab, ETH Zurich, Institute for Particle Physics and Astrophysics, Aix-Marseille Université, Canada–France–Hawaii Telescope, Université de Montréal, Institut de Planétologie et d'Astrophysique de Grenoble, Université Grenoble Alpes, University of Geneva, McGill University, Institut de Recherche en Astrophysique et Planétologie, Université de Toulouse, Ames Research Center, Université Paris Cité, Université Paris Sciences et Lettres, Observatoire de Paris, Laboratoire d’études spatiales et d’instrumentation en astrophysique, Polytechnique Montréal
Language: English
Subfield: Astronomy and Astrophysics
Field: Physics and Astronomy
Domain: Physical Sciences
Open Access status: gold
Estimated APC paid: $1,865
Funders: National Aeronautics and Space Administration, California Institute of Technology, Space Telescope Science Institute, Schweizerischer Nationalfonds zur Förderung der Wissenschaftlichen Forschung, Conselho Nacional de Desenvolvimento Científico e Tecnológico, Fundação de Amparo à Pesquisa do Estado de Minas Gerais, Ames Research Center, Science Mission Directorate, Fonds de recherche du Québec – Nature et technologies
OpenAlex ID: W7171956557