Andres Carmona

Context. Exoplanetary magnetic fields govern atmospheric escape and circulation but have eluded detection in close-in planets. In the ultra-hot Jupiter KELT-9b, atmospheric dynamo is predicted to generate atmospheric fields of 400−4000 G. Aims. We searched for the circular polarization in atomic lines that a magnetic field would imprint, through the Zeeman effect, on the transmission spectrum of KELT-9b. Methods. We observed three transits with SPIRou at the CFHT, on 07 September 2025 and 03 and 06 July 2026, and applied least squares deconvolution to 1398 atomic lines to map the transit-averaged Stokes V and null spectra against the orbital semi-amplitude, K _p , and systemic velocity, v _sys . Results. The 2025 transit shows a Stokes V signature of V / I _c = 9.3 × 10 ⁻⁵ at K _p = 219 ± 11 km s ⁻¹ , v = −34.0 ± 1.2 km s ⁻¹ , close to the expected planetary velocity. Its false-alarm probability is 1.9 × 10 ⁻⁴ , and thus it is formally a marginal detection. Both 2026 transits are of comparable sensitivity but neither exhibits a signal at that location, setting 3 σ limits of 4.9 and 6.0 × 10 ⁻⁵ ; the 2025 amplitude would have been recovered at 4.9 σ and 4.0 σ . Conclusions. The 2025 signature is robust to the tests we applied to it but qualifies as a marginal detection at best. Spurious signals of comparable strengths occur elsewhere in our Stokes V and null maps, and we cannot rule out that our marginal detection is excess noise. It is not reproduced ten months later.

We report excess absorption in the metastable He i triplet at 1083 nm during a transit of HIP 67522b, a 17 Myr old, very low-density giant planet. On 2026 January 20, we observed the last 1.9 hr of a transit and 1.4 hr after egress with VLT/CRIRES+ ( Y band, R ≈ 10 ⁵ ). Relative to the last post-egress spectra, full-transit spectra show excess absorption of 3.2% ± 0.3% (equivalent width 65 ± 7 mÅ, 10 σ ), blueshifted by 28 ± 4 km s ⁻¹ (19–33 km s ⁻¹ across fits) from the planet’s radial velocity. The absorption decreases gradually through the time series and remains detectable 0.5–1 hr after egress, suggesting escaping gas trailing the planet over several planetary radii. The reference may still contain planetary helium, so these values are lower limits. A contribution from the flaring star cannot be excluded. If planetary in origin, HIP 67522b is the youngest planet with a secure detection of escaping helium.

The TRAPPIST-1 system is well known for its seven transiting Earth-sized exoplanets. It has been extensively studied and characterized, notably with transit timing variations (TTVs), to precisely measure the mass of the planets. Using near-infrared spectroscopic observations obtained as part of the SPIRou Legacy Survey and the NIRPS Guaranteed Time Observation programs, we aimed to verify those values through radial velocity (RV) measurements of the system. Our RV analysis reveals that the current data do not have the precision required to individually detect the TRAPPIST-1 planets. However, we confidently detect (Δ ln 𝒵 = 7.53, 1860:1 odds) the combined RV signature of the planets by using the relative masses derived from the TTV analysis, with TRAPPIST-1 b as a proxy for the whole system. For the first time, the RV signal of the TRAPPIST-1 system is recovered: we find a RV semi-amplitude of K _b = 3.65 _−0.83 ^+0.78 m s ⁻¹ . This corresponds to a planetary mass of M _{p , b} = 1.31 ± 0.29 M _⊕ and demonstrates that the RV measurements are consistent with the TTV model ( M _{p , b; TTV} = 1.374 ± 0.069 M _⊕ ). Additionally, the NIRPS RVs constrain the presence of giant planets beyond the snow line, excluding Saturn-mass planets out to 2.7-yr orbits and Neptune-mass objects out to 20 d. Through RV, we determined the stellar activity period to be of 3.22 _−0.20 ^+0.22 d. Its agreement with photometric measurements (K2 and TESS) confirms stellar rotation as the origin of the ~3.3-d periodicity observed for TRAPPIST-1. We further investigated stellar activity with SPIRou polarimetric measurements, and placed an upper limit on the longitudinal field (| B _l | < 40 G, 3 σ ). This limit is compatible with a weak multipolar large-scale magnetic geometry, as observed in some of the later-type rapidly rotating M dwarfs.

High-resolution spectroscopy provides unique constraints on exoplanet atmospheric composition and dynamics. The past decade of ground-based campaigns has accumulated extensive public archives, but many observations remain to be analyzed. We present a homogeneous blind-search analysis of 50 SPIRou transits spanning 14 exoplanets, ranging from super-Earths to ultrahot Jupiters, combining data from large program and public archived observations. Using an automated data reduction and atmospheric retrieval via nested sampling validated by cross-correlation function analysis, we confirm previous H ₂ O and CO detections in HD 189733 b, WASP-76 b, and WASP-127 b, report tentative H ₂ S detections in HD 189733 b and TOI-1807 b, a tentative detection of the GJ 3470 b atmosphere, and provide upper limits for non-detections. This work demonstrates a scalable method for systematic archive analysis, providing a first step toward ground-based support of large space-based atmospheric characterization programs and the study of atmospheric diversity across exoplanet populations from a statistical perspective.

In this paper, we present new spectropolarimetric and velocimetric observations of the prototypical classical T Tauri star TW Hya obtained with SPIRou at the Canada-France-Hawaii Telescope, expanding our previous monitoring over two new seasons (2024 and 2025). We confirm that the large-scale magnetic field of TW Hya varied with time and find that it showed fluctuations on a timescale of about a year in addition to the longer term variations outlined in the previous study. Using Zeeman-Doppler imaging, we find that the large-scale field of TW Hya mostly consists of a poloidal dipole of mean polar strength 0.83 kG, inclined at an average 17° to the rotation axis. We also find that the radial velocities of TW Hya, once fully filtered from telluric contamination, were dominated by rotational modulation induced by activity, with residuals of 32 m s ⁻¹ rms. No signal from a putative close-in planet is found, with an upper limit on the planet mass ranging from 0.33 to 0.98 M for distances of 0.053 to 0.41 au from the central star. Emission lines indicate that the mass-accretion rate was equal to 10 ^{−8.33±0.20} M _⊙ yr ⁻¹ on average, with peak-to-peak fluctuations by a factor of ≃5 from season to season. This confirms that accretion onto TW Hya is unstable, with the magnetospheric gap carved by the large-scale field at the center of the disk extending to no further than 33–40% of the corotation radius on average, where the disk’s Keplerian angular velocity equals the rotation rate at the stellar surface.

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.

Context . Detecting and characterizing the atmosphere of rocky planets in the habitable zone is a key objective of exoplanet research in the era of JWST and the upcoming E-ELT. Spectroscopy of a planetary transit is the primary method of obtaining a transmission spectrum of an exoplanetary atmosphere. A lunar eclipse is a natural proxy for an Earth transit, offering a unique opportunity to study Earth’s atmosphere as if it were an exoplanet. Aims . This work aims to derive the empirical, wavelength-dependent effective height of Earth’s atmosphere in the near-infrared, spanning the Y to K bands. Methods . During a lunar eclipse, the penumbra – the region where the Sun is partially occulted by the Earth – contains the signature of the transmission spectrum of the atmosphere along Earth’s limb. The high-resolution (R=70 000) SPIRou spectrograph at CFHT was used to collect spectra during and after the November 19, 2021 eclipse. Two distinct methods, using either one or two penumbral spectra, were employed to derive the effective height of the atmosphere. Each method was evaluated in the context of distinct astrometric and spectrophotometric approaches. Results . The derived effective height spans 964 to 2498 nm and shows the absorption bands of H ₂ O, O ₂ , CH ₄ , and CO ₂ peaking at up to 29.6 km at a spectral resolution of R=70 000, including a 12.7 km offset defining a reference altitude taken from a transit model. The uncertainty assessed from individual penumbra observations and from uncertainties on telluric lines correction and Moon reflectance is found to be 3 σ ≈ 3.6 km. Heights are up to 25.1 km at a convolved resolution of R=1000. Conclusions . The measured heights are in good agreement with theoretical predictions. The high-resolution wavelength-dependent effective heights are made publicly available to the community.

Context. M dwarfs are the most abundant stars in the Galaxy and exhibit diverse magnetic behaviours. While understanding their large-scale magnetic fields is essential for investigating stellar dynamos and assessing the impact of magnetic activity on planetary environments, their magnetic properties and long-term variability remain poorly characterised. Aims. Our aim was to characterise the large-scale magnetic fields of six M dwarfs in the southern PLATO field, with rotation periods ranging from approximately 1 to 17 days and masses between 0.26 and 0.64 M _⊙ . Five of these stars are partially convective, while one is fully convective. These targets extend the mass–rotation diagram into previously unsampled regions. Methods. We analysed TESS light curves to determine accurate rotation periods and optimise phase coverage for our spectropolarimetric observations. SPIRou data were reduced to obtain least-squares deconvolution (LSD) profiles and longitudinal field measurements, while synthetic spectra fitting yielded small-scale field strengths. We then applied ZDI to reconstruct the large-scale magnetic topologies of the six targets. Results. We report a wide diversity of magnetic topologies among the six M dwarfs, with three main results: (1) Rapidly rotating ( P _rot < 2 d) early M dwarfs can generate dipole-dominated magnetic fields of moderate intensity, similar to those of less massive mid-M dwarfs; (2) Rapidly rotating mid-M dwarfs can generate non-axisymmetric large-scale magnetic fields featuring a significant toroidal component; (3) We report a moderately rotating ( P _rot ∼ 17 d) early M dwarf featuring a surprisingly weak large-scale magnetic field. Conclusions. Our findings further highlight the diversity of magnetic field configurations among M dwarfs, including in previously unexplored regions of parameter space. Long-term monitoring of our sample is crucial in order to distinguish persistent features from variability-driven excursions and to characterise the long-term evolution of their surface magnetic fields. Complementary PLATO photometry, including flare and spot-induced variability analyses, will be essential to link surface activity with magnetic properties.

Context. Studies of magnetospheric accretion and magnetic field topology in T Tauri stars have advanced over the years, but their applications to fully convective, very-low-mass T Tauri stars remain relatively unexplored. Aims. We aim to analyze the circumstellar environment of the very-low-mass dipper-like star JH 223 by investigating the accretion process and characterizing its large-scale magnetic field topology. Methods. We analyzed the photometric variability of JH 223 using observations from multiple telescopes, including K2, TESS, and LCOGT across different epochs. Additionally, we used Gemini/GRACES spectroscopic and CFHT/SPIRou spectropolarimetric data to investigate the star-disk interaction and to characterize the large-scale stellar magnetic field using Zeeman-Doppler imaging. Results. JH 223 is a fully convective classical T Tauri star with an age of about 3 Myr and a mass of 0.4 M _⊙ . The large-scale surface magnetic field is predominantly poloidal, with a 250 G dipolar component. The dipole field strength and the mass accretion rate indicate that the disk gas truncation radius is located near the corotation radius (6 ± 1 R _★ ). The star-disk interaction, combined with the inclined dipole, generates accretion columns that warp the inner disk. As the star rotates, this warp periodically obscures the stellar surface every 3.31 days, producing the dipper light curves. The same period is also detected in variations of the radial velocity and the longitudinal magnetic field. The accretion columns, traced by strong redshifted absorption components in H α and He I 1083nm, are associated with the inner disk warp, as they occur around the same rotational phase. The accretion process in JH 223 is dynamic, transitioning from an unstable to a stable regime over a few weeks, consistent with predictions from magnetohydrodynamic simulations of the star-disk interaction. Conclusions. Results from multi-technique observations suggest that the magnetospheric accretion model remains valid for fully convective very-low-mass young stars.

Tracing the compositional link between terrestrial super-Earths and their host stars provides clues about their dominant formation pathway. By constraining the stellar abundances of refractory elements, we can predict the core mass fractions (CMFs) of their super-Earths. The level of agreement between this prediction and the planetary CMF derived from their masses and radii can reveal past formation processes, such as mantle stripping and water-rich formation plus sequestration in the planet core. We present the first results from the Near Infrared Planet Searcher (NIRPS) GTO CMF subprogram: an intensive radial velocity campaign to refine masses and compute host stellar abundances of three hot super-Earths around M dwarfs (GJ1132 b, GJ1252 b, and LTT 3780 b). We calculated masses of 1.69 ± 0.15 M _⊕ , 1.54 ± 0.18 M _⊕ , and 2.34 ± 0.10 M _⊕ respectively. We measured the CMFs of these and six further hot super-Earths with masses already available in the literature to a precision of 10–15%. We compared them to CMF predictions made from measuring the Fe, Mg, and Si abundances of their host stars measured from the NIRPS spectra. The CMFs of these planets are smaller than expected from their host stellar abundances to a statistically significant degree. This discrepancy is suggestive of significant reservoirs of water, and while these planets are too hot to harbor surface water, they likely have interior water mass fractions of ~1%.