Pia Cortes Zuleta

Context . LHS 3844 b (TOI-136b) is an ultra short-period, Earth-size exoplanet detected by TESS. It is one of the most favourable objects for atmospheric characterisation and study of its surface with the James Webb Space Telescope. However, the dynamical mass of this planet has not yet been measured. Aims . We aim to determine the mass of LHS 3844 b using high-precision radial velocity (RV) measurements and assess the robustness of the inferred signal across different noise and orbital modelling assumptions. Methods . We analyse 25 ESPRESSO RV observations within a fully Bayesian framework. We explore 15 competing RV models that differ in their treatment of correlated stellar variability (through different Gaussian process (GP) kernels) and long-term drifts. Marginal likelihoods are computed for all models and used for Bayesian model comparison and evidence-weighted parameter estimation. Results . The RV planetary signal is robustly detected across all models, and the inferred semi-amplitude remains stable under all tested noise and drift prescriptions. From the evidence-weighted posterior samples we derive a planetary mass of 2.27 ± 0.23 M _⊕ and a bulk density of 5.67 ± 0.65 gcm ⁻³ , consistent with a predominantly rocky composition. Model comparison favours GP kernels including periodic or quasi-periodic components associated with stellar rotation and disfavours models with additional long-term drifts. Using interior-structure inference, we find that the core mass fraction is comparable to (or slightly smaller than) Earth's and only trace amounts of water are permitted, supporting a dry, terrestrial interior. We also investigate a tentative additional signal near ~6.9 days, but Bayesian model comparison does not provide conclusive support for its planetary interpretation. Conclusions . We report the first dynamical mass measurement of LHS 3844 b, confirming it as a dense, terrestrial ultra-short-period planet. With its exceptionally well-constrained bulk properties and extensive JWST programme, LHS 3844 b remains a benchmark target for studies of the atmospheres and surfaces of rocky exoplanets.

We present the TESS-based discoveries of planetary systems orbiting the late G dwarfs TOI-2494 and TOI-5143, each of which harbors a hot giant planet and a smaller interior planet. TOI-2494 hosts a transiting mini-Neptune ( P = 2.41 days, R P = 2.3 5 − 0.15 + 0.16 R _⊕ ) and a hot Saturn ( P = 8.38 days) with grazing transits, while TOI-5143 hosts a transiting mini-Neptune ( P = 2.38 days, R P = 2.7 3 − 0.17 + 0.19 R _⊕ ) and a hot Jupiter ( P = 5.21 days) with grazing transits. We measure the masses of TOI-2494 c (80 ± 19 M _⊕ ) and TOI-5143 c (208 ± 14 M _⊕ ), place upper limits on the masses of the smaller planets, and explore the architectures of the planetary systems. TOI-2494 c and TOI-5143 c join a small but growing number of short-period giant planets known to be flanked by smaller companions. While the absence of close neighbors to most hot Jupiters would be consistent with disruptive dynamical evolution, the presence of nearby small planets in some hot Jupiter systems points to a separate, dynamically quiet formation pathway. In support of this conclusion, we present preliminary evidence that hot giant planets with small nearby companions tend to have low mutual orbital inclinations, consistent with the mutual inclination distribution of the dynamically quiet population of compact systems of multiple super-Earths and mini-Neptunes.

Caractérisation de l'activité stellaire des naines M par spectroscopie de haute précision dans l'optique et le proche infrarouge pour la recherche de planètes de faible masse: Les naines M sont devenues des cibles privilégiées pour la détection et la caractérisation des exoplanètes. Leur faible masse en fait des cibles idéales pour effectuer des relevés de vitesse radiale (VR) puisque, pour une masse donnée, la force gravitationnelle de la planète sera plus importante que pour les étoiles semblables au Soleil. Cependant, les naines M sont connues pour être des étoiles magnétiquement actives. L'activité stellaire est actuellement l'une des principales limites à la détection des planètes de faible masse, car elle induit des variations quasi-périodiques du VR de l'ordre de quelques mètres par seconde. Cette thèse vise à étudier l'activité stellaire des naines M en utilisant la spectroscopie de haute précision dans les domaines optique et proche infrarouge afin d'améliorer la détection des planètes de faible masse. Dans le domaine du proche infrarouge, j'ai utilisé la spectroscopie de haute précision et la spectropolarimétrie de SPIRou, qui est monté sur le télescope Canada-France-Hawaii. Le calcul de la vitesse radiale des naines M est encore difficile dans le proche infrarouge en raison de la grande quantité de raies telluriques dans leurs spectres. D'une part, j'ai travaillé en étroite collaboration avec l'équipe du système de réduction des données et j'ai effectué plusieurs tests pour mesurer l'impact de la sélection des masques dans le calcul du CCF. D'autre part, j'ai développé des outils informatiques pour obtenir des indicateurs d'activité à partir des spectres SPIRou basés sur la forme du CCF et sur la largeur pseudo-équivalente des lignes spectrales dans le domaine SPIRou. J'ai testé leurs performances sur un échantillon de naines M. Dans le domaine optique, j'ai travaillé avec le spectrographe SOPHIE situé à l'Observatoire de Haute Provence. Une douzaine d'étoiles de type M sont suivies quasi-simultanément avec SOPHIE et SPIRou afin d'améliorer la caractérisation de la variation de l'activité stellaire dans l'optique et le proche infrarouge. J'ai utilisé l'algorithme de template-matching NAIRA pour calculer les vitesses radiales de SOPHIE et les indicateurs d'activité. J'ai dirigé la première publication d'une cible SOPHIE+SPIRou, la naine M Gl 205, sur laquelle j'ai effectué une analyse approfondie du signal d'activité stellaire dans les deux domaines en utilisant la technique du processus gaussien. J'ai analysé les VRs et les indicateurs d'activité de l'échantillon complet SOPHIE+SPIRou pour rechercher des périodicités liées à l'activité stellaire et aux planètes. J'ai identifié deux cibles intéressantes avec des signaux compatibles dans l'optique et le proche infrarouge. Une deuxième publication est en préparation avec une analyse détaillée de l'activité stellaire et un possible signal Keplerienne

GJ 887 is a bright M dwarf in the solar neighborhood with two currently reported nontransiting exoplanets with periods of 9 d and 21 d, along with an additional unconfirmed signal at 50 d. We reanalyzed the system with 101 new HARPS and 12 new ESPRESSO radial velocities (RVs) secured with a cadence to confirm or refute the origin of the 50 d signal. To do so, we searched for signals related to stellar activity in photometric data and spectroscopic indicators. We modeled the stellar activity in the RVs with Gaussian processes (GPs). With the Bayesian analysis, we confirmed a four-planet model, including the two previously known planets at periods of 9.2619 ± 0.0005 d and 21.784 ± 0.004 d, as well as two newly confirmed exoplanets: an Earth-mass planet, with a 4.42490 ± 0.00014 d period and a sub-meter-per-second amplitude, and a super-Earth with a 50.77 ± 0.05 d period located in the habitable zone (HZ). This super-Earth is the second closest planet in the HZ, after Proxima Cen b. We found an additional signal in a 2:1 resonance with the 4.4 d planet at 2.21661 ± 0.00010 d with an amplitude of 0.37 ± 0.09 m/s, which could be related to an additional planet. However, other explanations of its origin are also plausible. This signal remains a candidate, as further investigation is required to confirm its true nature. If the signal is caused by a planet, its minimum mass would be half that of Earth. We measured the stellar rotation period with the characteristic periodic timescale of the GP. We found a period of 38.7 ± 0.5 d, which is consistent with the rotation period determined from photometry and other activity indices.

Context. The HARPS-N solar telescope has been observing the Sun every possible day since the summer of 2015. We have recently released 10 years of these data, which are available online. Aims. The goal of this paper is to present the different optimisations made to the ESPRESSO data reduction software used to extract the published HARPS-N solar spectra, describe the data curation, and perform some analyses that demonstrate the extreme radial velocity (RV) precision of those data. Methods. By analysing all of the HARPS-N wavelength solutions over 13 years, we brought to light instrumental systematics at the 1 m s ⁻¹ level. We mitigated those systematics by curating the thorium line list used to derive the wavelength solution and applying a correction to the drift of thorium lines induced by the aging of thorium-argon hollow cathode lamps. After optimisation, we demonstrated a peak-to-peak precision on the HARPS-N wavelength solution better than 0.75 m s ⁻¹ over 13 years. We then carefully curated the decade of HARPS-N re-reduced solar observations by rejecting 30% of the data affected either by clouds, bad atmospheric conditions, or well-understood instrumental systematics. Finally, we corrected the curated data for spurious sub-meter-per-second RV effects caused by erroneous instrumental drift measurements and by changes in the spectral blaze function over time. Results. After curation and correction, a total of 109,466 HARPS-N solar spectra and respective RVs over a decade were made available. The median photon-noise precision of the RV data is 0.28 m s ⁻¹ , and on daily timescales, the median RV rms is 0.49 m s ⁻¹ , which is similar to the level imposed by stellar granulation signals. On 10 year timescales, the large RV rms of 2.95 m s ⁻¹ results from the RV signature of the Sun’s magnetic cycle. Through modelling of this long-term effect using the Bremen composite magnesium II activity index, we demonstrate a long-term RV precision of 0.41 m s ⁻¹ . We also analysed contemporaneous HARPS-N and NEID solar RVs and found the data from both instruments to be of similar quality and precision. However, an analysis of the RV difference between these two RV datasets over the three available years gave a surprisingly large RV rms of 1.3 m s ⁻¹ . This variation is dominated by an unexplained trend that could be caused by a different sensitivity to stellar activity of the two datasets. Once this trend was modelled, the overall RV rms for three years reached 0.79 m s ⁻¹ , and the RV rms during the low-activity phase decreased to 0.6 m s ⁻¹ , compatible with what is expected from supergranulation. Conclusions. This decade of high-cadence HARPS-N solar observations with short- and long-term precision below one m s ⁻¹ represents a crucial dataset in the pursuit of further understanding the stellar activity signals in solar-type stars and advancing other science cases requiring such extreme precision.

Context . M dwarfs are prime targets in the search for exoplanets because of their prevalence and because low-mass planets can be better detected with radial velocity (RV) methods. In particular, the near-infrared (NIR) spectral domain offers an increased RV sensitivity and potentially reduced stellar activity signals. Precise NIR RV measurements are strongly affected by telluric absorption lines from the Earth’s atmosphere, however. Aims . We searched for planets orbiting Gl 725 B, a nearby late-M dwarf located at 3.5 pc, using high-precision SPIRou RV observations. We also assessed the effect of telluric contamination on these measurements and evaluated the performance of the weighted principal component analysis reconstruction ( wapiti ) method, which is a weighted principal component analysis (wPCA) approach designed to mitigate these systematics and to improve the sensitivity of planet detections. Methods . Using synthetic and observational SPIRou data, we simulated the effect of telluric lines on RV data under varying barycentric Earth radial velocity (BERV) conditions. We then applied the wapiti method for identifying and correcting telluric-induced systematics in line-by-line RVs. The method was tested through an injection-recovery test on simulated data and was subsequently applied to real SPIRou observations of Gl 725 B. Results . wapiti successfully corrects telluric contamination in simulated and real datasets. This enhances the detectability and accuracy of planetary signals. In the corrected Gl 725 B dataset, we identified a two-planet system composed of a candidate inner planet (Gl 725 Bb), with periods of 4.765 ± 0.004 days and a semi-amplitude of 1.4 ± 0.3 m s ⁻¹ , and a confirmed planet Gl 725 Bc, with a period of 37.90 ± 0.17 days and a semi-amplitude of 1.7 ± 0.3 m s ⁻¹ . Their minimum mass is 1.5 ± 0.4 M _⊕ and of 3.5 ± 0.7 M _⊕ , respectively, and the outer planet is located in the habitable zone of its host star. Using a multi-dimensional Gaussian process framework to model and correct for stellar activity, we also recovered a stellar rotation period of 105.1 ± 3.3 days.

Context. In the search for exoplanets using radial velocities (RV), stellar activity has become one of the main limiting factors for detectability. Fortunately, activity-induced RV signals are wavelength-dependent or chromatic, unlike planetary signals. This study exploits the broad spectral coverage provided by the combined use of SOPHIE and SPIRou velocimeters to investigate the chromatic nature of the activity signal of the highly active M dwarf EV Lac. Aims. We aim to understand the origin of the strong wavelength dependence (chromaticity) observed in the RV signal of EV Lac by selecting spectral lines based on physical properties. In particular, we explore the impact of starspots by defining the contrast effect at the level of individual lines. The Zeeman effect is also considered in this study. Methods. SPIRou and SOPHIE spectra were reduced using the line-by-line (LBL) method. We performed custom RV calculations, using groups of spectral lines selected for their sensitivity to either the spot-to-photosphere contrast or the Zeeman effect. The sensitivity of each line to the spot is defined using a two-temperature model based on PHOENIX spectra, while Landé factors were used to quantify Zeeman sensitivity. Results. We find that the spectral lines are distributed in two distinct families of contrasts, producing anti-correlated RV signals. This leads to a partial cancellation of the total RV signal, especially at longer wavelengths and provides a natural explanation for the strong chromaticity observed in EV Lac. This sign-reversal effect is demonstrated here, for the first time, on empirical data. Building on this discovery, we propose a new approach to constraining spot temperatures and to mitigating stellar activity. This will open up promising avenues for improving activity corrections and enhancing the detection of exoplanets around active M dwarfs.

Context. The search for exoplanets around nearby M dwarfs represents a crucial milestone in the census of planetary systems in the vicinity of our Solar System. Aims. Since 2018 our team has been conducting a blind search program for planets around nearby M dwarfs with the near-IR spectro-polarimeter and velocimeter SPIRou at the Canada-France-Hawaii Telescope and with the optical velocimeter SOPHIE at the Haute-Provence Observatory in France. The aim of this paper is to present our results on Gl 410, a 0.55 M_⊙ 480 ± 150 Myr old active M dwarf distant 12 pc. Methods. We searched for planetary companions using radial velocities (RVs). We used the line-by-line (LBL) technique to measure the RVs with SPIRou and the template matching method with SOPHIE. Three different methods were employed, two based on principal component analysis (PCA), to clean the SPIRou RVs for systematics. We applied Gaussian processes (GP) modeling to correct the SOPHIE RVs for stellar activity. The ℓ₁ and apodized sine periodogram analysis was used to search for planetary signals in the SPIRou data taking into account activity indicators. We analyzed TESS data and searched for planetary transits. Results. We report the detection of a M sin(i) = 8.4 ± 1.3 M_⊕ sub-Neptune planet at a period of 6.020 ± 0.004 days in circular orbit with SPIRou. The same signal, although with lower significance, was also retrieved in the SOPHIE RV data after correction for activity using a GP trained on SPIRou’s longitudinal magnetic field (B_ℓ) measurements. The TESS data indicate that the planet is not transiting. Within the SPIRou wPCA RVs, we find tentative evidence for two additional planetary signals at 2.99 and 18.7 days. Conclusions. Infrared RVs are a powerful method to detect extrasolar planets around active M dwarfs. Care should be taken, however, to correct or filter systematics generated by residuals of the telluric correction or small structures in the detector plane. The LBL technique combined with PCA offers a promising way to reach this objective. Further monitoring of Gl 410 is necessary.

While several thousand exoplanets are now confirmed, the number of known transiting warm Jupiters (10 d < period < 200 d) remains relatively small. These planets are generally believed to have formed outside the snowline and migrated to their current orbits. Because they are sufficiently distant from their host stars, they mitigate proximity effects and so offer valuable insights into planet formation and evolution. Here, we present the study of seven systems, three of which – TOI-2295, TOI-2537, and TOI-5110 – are newly discovered planetary systems. Through the analysis of TESS photometry, SOPHIE radial velocities (RVs), and high-spatial resolution imaging, we found that TOI-2295b, TOI-2537b, and TOI-5110b are transiting warm Jupiters with orbital periods ranging from 30 to 94 d, masses between 0.9 and 2.9 M_J, and radii ranging from 1.0 to 1.5 R_J. Both TOI-2295 and TOI-2537 harbor at least one additional, outer planet. Their outer planets – TOI-2295c and TOI-2537c – are characterized by orbital periods of 966.5_-4.2^+4.3 and 1920_-140⁺²³⁰ d, respectively, and minimum masses of 5.61_-0.24^+0.23 and 7.23_-0.45^+0.52 M_J, respectively. We have also investigated and characterized the two recently reported warm Jupiters TOI-1836b and TOI-5076b, which we independently detected in SOPHIE RVs. Our new data allow for further discussion of their nature and refinement of their parameters. Additionally, we study the planetary candidates TOI-4081.01 and TOI-4168.01. For TOI-4081.01, despite our detection in RVs, we cannot rule out perturbation by a blended eclipsing binary, and we thus exercise caution regarding its planetary nature. On the other hand, we identify TOI-4168.01 as a firm false positive; its RV curve exhibits a large amplitude in an antiphase relation with the transit ephemeris observed by TESS, indicating that the detected event is the eclipse of a secondary star rather than a planetary transit. Finally, we highlight interesting characteristics of these new planetary systems. The transits of TOI-2295b are highly grazing, with an impact parameter of 1.056_-0.043^+0.063. This leaves its radius uncertain but potentially makes it an interesting probe of gravitational dynamics in its two-planet system, as transit shapes for grazing planets are highly sensitive to even small variations in inclination. TOI-2537b, in turn, is a temperate Jupiter with an effective temperature of 307±15 K and can serve as a valuable low-irradiation control for models of hot Jupiter inflation anomalies. We also detected significant transit timing variations (TTVs) for TOI-2537b, which are likely caused by gravitational interactions with the outer planet TOI-2537c. Further transit observations are needed to refine the analysis of these TTVs and enhance our understanding of the system’s dynamics. Finally, TOI-5110b stands out due to its orbital eccentricity of 0.745_-0.027^+0.030, one of the highest planetary eccentricities discovered thus far. We find no conclusive evidence for an external companion, but an unseen planet with a semi-amplitude smaller than 10 m/s could nonetheless still be exciting its eccentricity.