Revisiting TOI-4438 and TOI-442 planetary systems with new observations from SPIRou and TESS
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.
Related
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- Radial velocity detection of the TRAPPIST-1 planetary system with SPIRou and NIRPS
BibTeX
@article{bell2026revisiting,
title = {{Revisiting TOI-4438 and TOI-442 planetary systems with new observations from SPIRou and TESS}},
author = {J. Serrano Bell and G. Hébrard and E. Martioli and R. Díaz and L. de Almeida and D. Lorenzo-Oliveira and A. Salmi and C. Dorn and M. Valatsou and A. Carmona and M. Ould-Elhkim and L. Arnold and É. Artigau and I. Boisse and X. Bonfils and C. Cadieux and Z. Chakir and N. Cook and X. Delfosse and J.-F. Donati and R. Doyon and N. Heidari and J. Jenkins and F. Kiefer and S. Lafrance and A. L’heureux and C. Moutou and J. Morneau and X. Vandelac},
journal = {Astronomy \& Astrophysics - A\&A},
year = {2026},
month = sep,
doi = {10.1051/0004-6361/202659984},
url = {https://hal.science/hal-05803585v1},
note = {CC BY 4.0},
}
RIS
TY - JOUR
TI - Revisiting TOI-4438 and TOI-442 planetary systems with new observations from SPIRou and TESS
AU - J. Serrano Bell
AU - G. Hébrard
AU - E. Martioli
AU - R. Díaz
AU - L. de Almeida
AU - D. Lorenzo-Oliveira
AU - A. Salmi
AU - C. Dorn
AU - M. Valatsou
AU - A. Carmona
AU - M. Ould-Elhkim
AU - L. Arnold
AU - É. Artigau
AU - I. Boisse
AU - X. Bonfils
AU - C. Cadieux
AU - Z. Chakir
AU - N. Cook
AU - X. Delfosse
AU - J.-F. Donati
AU - R. Doyon
AU - N. Heidari
AU - J. Jenkins
AU - F. Kiefer
AU - S. Lafrance
AU - A. L’heureux
AU - C. Moutou
AU - J. Morneau
AU - X. Vandelac
PY - 2026
DA - 2026/09/16
JO - Astronomy & Astrophysics - A&A
DO - 10.1051/0004-6361/202659984
UR - https://hal.science/hal-05803585v1
AB - 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.
SN - 0004-6361
SN - 1432-0746
ER -