SPIRou detects two planets around the nearby M4.5V star GJ 4274

¹ Université de Toulouse, CNRS, IRAP, 14 av. Edouard Belin, 31400 Toulouse, France
² Univ. Grenoble Alpes, CNRS, IPAG, 38000 Grenoble, France
³ SUPA School of Physics and Astronomy, University of St Andrews, North Haugh, St Andrews KY16 9SS, UK
⁴ Institut Trottier de recherche sur les exoplanètes, Département de Physique, Université de Montréal, Montréal, Québec, Canada
⁵ Observatoire du Mont-Mégantic, Québec, Canada
⁶ Institut d’astrophysique de Paris, UMR7095 CNRS, Université Pierre & Marie Curie, 98bis boulevard Arago, 75014 Paris, France
⁷ Observatoire de Haute-Provence, CNRS, Université d’Aix-Marseille, 04870 Saint-Michel-l’Observatoire, France
⁸ Aix Marseille Univ, CNRS, CNES, LAM, Marseille, France

^★ Corresponding author: This email address is being protected from spambots. You need JavaScript enabled to view it.

Received: 13 October 2025
Accepted: 31 October 2025

Abstract

Context. M dwarfs are prime targets in the search for exoplanets due to their prevalence and the enhanced radial velocity (RV) detectability of low-mass planets. Recent advancements in instrumentation have extended RV observations from the optical to the near-infrared (nIR) domain, enabling more effective study of M dwarfs, which frequently host rocky planets. The nIR range offers increased RV sensitivity and potentially reduced stellar activity signals, making it particularly well suited for these stars.

Aims. We analyzed spectropolarimetric data of the M4.5V star GJ 4274, acquired using the nIR spectropolarimeter SPIRou, to characterize its stellar activity and to search for planetary signals. We additionally examined TESS photometric data to search for transits corresponding to the potential signals in the RV data.

Methods. In this study, we employed a line-by-line framework to derive and analyze the RV signal of GJ 4274 acquired with SPIRou. From the SPIRou spectra, we also derived and analyzed the longitudinal large scale magnetic field, B_ℓ, and the surface temperature variations, dTemp. We combined the SPIRou RV data with RV measurements from CARMENES, to model possible planetary signals with both circular and eccentric orbits. We modeled the activity with a quasiperiodic Gaussian process. We also performed injection-recovery tests on the photometric TESS data to assess transit detectability.

Results. We report the discovery of two exoplanets around the nearby M dwarf star GJ 4274. Both planets are in a circular orbit with respective periods of P_b = 1.6339 ± 0.0001 and P_c = 69.6_−1.1^+0.3d, the latter located beyond the habitable zone. From their RV semi-amplitude signals (_Kb = 5.10_−0.67^+0.70 m/s and K_c = 4.11 ± 0.64 m/s), we derive minimum masses of m_b sin i = 2.97_−0.50^+0.54M_⊕ and m_c sin i = 8.4 ± 1.3 M_⊕, respectively. Photometric observations from TESS rule out most transit scenarios, including for the inner planet, yielding a maximum inclination of i_b ≤ 83^° for planet b. We do not detect RV variations related to stellar magnetic activity in the SPIRou time series, despite a prominent large-scale magnetic field with an amplitude of up to ±206₋₆₂⁺¹⁵⁸ G. From the activity indicators, we derive a rotation period for the star of 4.600_−0.006^+0.011d.

Conclusions. The two reported planets belong to the sub-Neptune class. GJ 4274 b has one of the shortest orbital periods among planets orbiting <0.2 M_⊙ M dwarfs within 15 pc, while GJ 4274 c lies in a sparsely populated region of the mass–period diagram. Their discovery adds to the census of nearby planetary systems and provides promising targets for future surveys.