Caractérisation d'atmosphère d’exoplanètes par spectroscopie de transmission en présence d'hétérogénéités stellaires : impact et modélisation des régions actives occultées

Les hétérogénéités de surface des étoiles actives, telles que les taches et les facules, peuvent compliquer l'interprétation des spectres de transmission en introduisant des caractéristiques spectrales qui chevauchent celles d'atmosphère d'exoplanètes. Les courbes de lumière de transit d'HAT-P-18$\,$b et de WASP-52$\,$b, observées avec le mode SOSS de l'instrument NIRISS à bord du JWST, sont déformées par des occultations de taches. Avant le déploiement du JWST, ces régions actives étaient souvent simplement masquées, toutefois ceci peut mener à des mesures incorrectes des paramètres du transit. J'ai adapté et implémenté $\texttt{spotrod}$, un modèle de transit avec occultation de taches, dans l'outil $\texttt{Juliet}$ pour inférer conjointement les paramètres du transit et des taches occultées. J'ai ainsi ajusté les courbes de lumière de transit de ces deux Jupiters chaudes et récupéré la position de chaque tache, leur rayon et leur spectre de contraste, c'est-à-dire le rapport du flux de la tache sur le flux stellaire. J'ai contraint la température des taches et leur gravité de surface (pour prendre en compte les effets du champ magnétique local) en ajustant chaque spectre de contraste avec des spectres de modèles stellaires PHOENIX. Cependant, un certain degré de dégénérescence est présent, conduisant à une solution plus probable pour chaque tache, mais aussi à d'autres solutions qui ne peuvent être exclues. Le spectre de transmission d'HAT-P-18$\,$b nous a permis de détecter de l'H$_2$O (12,5$\,\sigma$) avec une abondance sub-solaire de $\log$ H$_2$O $\approx$ -4,4 $\pm$ 0,3, des nuages (7,4$\,\sigma$) et du CO$_2$ (7,3$\,\sigma$) dans l'atmosphère planétaire ainsi que des régions actives non occultées (5,8$\,\sigma$) qui imitent une pente de diffusion Rayleigh.Surface heterogeneities on active stars, such as starspots and faculae, can complicate the interpretation of transmission spectra and introduce spectral features that overlap those of exoplanetary atmospheres. The transit light curves of HAT-P-18$\,$b and WASP-52$\,$b, observed in the SOSS mode of the NIRISS instrument aboard the JWST, are deformed by spot-crossings. These active regions were often simply masked before the launch of the JWST; however, this can prevent the correct measure of transit parameters. I adapted and implemented $\texttt{spotrod}$, a model for transits of spotted stars, into the $\texttt{Juliet}$ tool to simultaneously infer the transit and occulted starspots parameters. I fitted the transit light curves of these two hot Jupiters and retrieved for each spot its position, radius and spot-to-stellar flux contrast spectrum. I constrained the spots' temperature and surface gravity $-$ attempting to capture the effects of the local magnetic pressure $-$ by fitting each contrast spectrum with PHOENIX stellar model spectra. However, some degree of degeneracy is present, leading to a most likely solution for each starspot and other solutions that cannot be excluded. The transmission spectrum of HAT-P-18$\,$b enabled us to detect H$_2$O (12.5$\,\sigma$) with a sub-solar abundance of $\log$ H$_2$O $\approx$ -4.4 $\pm$ 0.3, a cloud deck (7.4$\,\sigma$) and CO$_2$ (7.3$\,\sigma$) in the planetary atmosphere as well as unocculted active regions (5.8$\,\sigma$) which mimic a Rayleigh scattering slope

Transmission Spectroscopy of the Habitable Zone Exoplanet LHS 1140 b with JWST/NIRISS

LHS 1140 b is the second-closest temperate transiting planet to Earth with an equilibrium temperature low enough to support surface liquid water. At 1.730 ± 0.025 R ⊕, LHS 1140 b falls within the radius valley separating H2-rich mini-Neptunes from rocky super-Earths. Recent mass and radius revisions indicate a bulk density significantly lower than expected for an Earth-like rocky interior, suggesting that LHS 1140 b could be either a mini-Neptune with a small envelope of hydrogen (∼0.1% by mass) or a water world (9%–19% water by mass). Atmospheric characterization through transmission spectroscopy can readily discern between these two scenarios. Here we present two JWST/NIRISS transit observations of LHS 1140 b, one of which captures a serendipitous transit of LHS 1140 c. The combined transmission spectrum of LHS 1140 b shows a telltale spectral signature of unocculted faculae (5.8σ), covering ∼20% of the visible stellar surface. Besides faculae, our spectral retrieval analysis reveals tentative evidence of residual spectral features, best fit by Rayleigh scattering from a N2-dominated atmosphere (2.3σ), irrespective of the consideration of atmospheric hazes. We also show through Global Climate Models (GCMs) that H2-rich atmospheres of various compositions (100×, 300×, 1000× solar metallicity) are ruled out to >10σ. The GCM calculations predict that water clouds form below the transit photosphere, limiting their impact on transmission data. Our observations suggest that LHS 1140 b is either airless or, more likely, surrounded by an atmosphere with a high mean molecular weight. Our tentative evidence of a N2-rich atmosphere provides strong motivation for future transmission spectroscopy observations of LHS 1140 b

Atmospheric Reconnaissance of TRAPPIST-1 b with JWST/NIRISS: Evidence for Strong Stellar Contamination in the Transmission Spectra

TRAPPIST-1 is a nearby system of seven Earth-sized, temperate, rocky exoplanets transiting a Jupiter-sized M8.5V star, ideally suited for in-depth atmospheric studies. Each TRAPPIST-1 planet has been observed in transmission both from space and from the ground, confidently rejecting cloud-free, hydrogen-rich atmospheres. Secondary eclipse observations of TRAPPIST-1 b with JWST/MIRI are consistent with little to no atmosphere given the lack of heat redistribution. Here we present the first transmission spectra of TRAPPIST-1 b obtained with JWST/NIRISS over two visits. The two transmission spectra show moderate to strong evidence of contamination from unocculted stellar heterogeneities, which dominates the signal in both visits. The transmission spectrum of the first visit is consistent with unocculted starspots and the second visit exhibits signatures of unocculted faculae. Fitting the stellar contamination and planetary atmosphere either sequentially or simultaneously, we confirm the absence of cloud-free hydrogen-rich atmospheres, but cannot assess the presence of secondary atmospheres. We find that the uncertainties associated with the lack of stellar model fidelity are one order of magnitude above the observation precision of 89 ppm (combining the two visits). Without affecting the conclusion regarding the atmosphere of TRAPPIST-1 b, this highlights an important caveat for future explorations, which calls for additional observations to characterize stellar heterogeneities empirically and/or theoretical works to improve model fidelity for such cool stars. This need is all the more justified as stellar contamination can affect the search for atmospheres around the outer, cooler TRAPPIST-1 planets for which transmission spectroscopy is currently the most efficient technique.Comment: 26 pages, 11 figures, accepted for publication in The Astrophysical Journal Letter

Near-Infrared Transmission Spectroscopy of HAT-P-18 \,b with NIRISS: Disentangling Planetary and Stellar Features in the Era of JWST

The JWST Early Release Observations (ERO) included a NIRISS/SOSS (0.6-2.8$\,\mu$m) transit of the $\sim\,$850$\,$K Saturn-mass exoplanet HAT-P-18$\,$b. Initial analysis of these data reported detections of water, escaping helium, and haze. However, active K dwarfs like HAT-P-18 possess surface heterogeneities $-$ starspots and faculae $-$ that can complicate the interpretation of transmission spectra, and indeed, a spot-crossing event is present in HAT-P-18$\,$b's NIRISS/SOSS light curves. Here, we present an extensive reanalysis and interpretation of the JWST ERO transmission spectrum of HAT-P-18$\,$b, as well as HST/WFC3 and $\textit{Spitzer}$/IRAC transit observations. We detect H$_2$O (12.5$\,\sigma$), CO$_2$ (7.3$\,\sigma$), a cloud deck (7.4$\,\sigma$), and unocculted starspots (5.8$\,\sigma$), alongside hints of Na (2.7$\,\sigma$). We do not detect the previously reported CH$_4$ ($\log$ CH$_4$ $<$ -6 to 2$\,\sigma$). We obtain excellent agreement between three independent retrieval codes, which find a sub-solar H$_2$O abundance ($\log$ H$_2$O $\approx -4.4 \pm 0.3$). However, the inferred CO$_2$ abundance ($\log$ CO$_2$ $\approx -4.8 \pm 0.4$) is significantly super-solar and requires further investigation into its origin. We also introduce new stellar heterogeneity considerations by fitting for the active regions' surface gravities $-$ a proxy for the effects of magnetic pressure. Finally, we compare our JWST inferences to those from HST/WFC3 and $\textit{Spitzer}$/IRAC. Our results highlight the exceptional promise of simultaneous planetary atmosphere and stellar heterogeneity constraints in the era of JWST and demonstrate that JWST transmission spectra may warrant more complex treatments of the transit light source effect

Awesome SOSS: Transmission Spectroscopy of WASP-96b with NIRISS/SOSS

The future is now - after its long-awaited launch in December 2021, JWST began science operations in July 2022 and is already revolutionizing exoplanet astronomy. The Early Release Observations (ERO) program was designed to provide the first images and spectra from JWST, covering a multitude of science cases and using multiple modes of each on-board instrument. Here, we present transmission spectroscopy observations of the hot-Saturn WASP-96b with the Single Object Slitless Spectroscopy (SOSS) mode of the Near Infrared Imager and Slitless Spectrograph, observed as part of the ERO program. As the SOSS mode presents some unique data reduction challenges, we provide an in-depth walk-through of the major steps necessary for the reduction of SOSS data: including background subtraction, correction of 1/f noise, and treatment of the trace order overlap. We furthermore offer potential routes to correct for field star contamination, which can occur due to the SOSS mode's slitless nature. By comparing our extracted transmission spectrum with grids of atmosphere models, we find an atmosphere metallicity between 1x and 5x solar, and a solar carbon-to-oxygen ratio. Moreover, our models indicate that no grey cloud deck is required to fit WASP-96b's transmission spectrum, but find evidence for a slope shortward of 0.9$\mu$m, which could either be caused by enhanced Rayleigh scattering or the red wing of a pressure-broadened Na feature. Our work demonstrates the unique capabilities of the SOSS mode for exoplanet transmission spectroscopy and presents a step-by-step reduction guide for this new and exciting instrument.Comment: MNRAS, in press. Updated to reflect published versio

Kétamine par voie orale pour le traitement du syndrome douloureux régional complexe réfractaire d’une patiente âgée de 36 ans

RésuméObjectif : Cet article présente un cas de syndrome douloureux régional complexe réfractaire aux traitements classiques et ayant répondu à un traitement par kétamine par voie orale. L’article passe également en revue le traitement du syndrome douloureux régional complexe.Résumé du cas : Il s’agit d’une femme de 36 ans atteinte d’un syndrome douloureux régional complexe de type I au pied gauche, en contexte ambulatoire. Elle a essayé de nombreux traitements et a dû cesser les exercices de réadaptation en raison de la douleur. Après avoir consulté un médecin d’une clinique externe contre la douleur chronique, elle a commencé un traitement par kétamine par voie orale. Les douleurs ont diminué de façon importante avec la prise de kétamine et la patiente a pu recommencer un programme de réadaptation.Discussion : Le syndrome douloureux régional complexe doit être pris en charge rapidement pour éviter que les douleurs ne persistent sur le long terme. Plusieurs traitements pharmacologiques ont été évalués pour ce syndrome, mais il existe peu de données dans la documentation scientifique sur la kétamine par voie orale pour le traitement du syndrome douloureux régional complexe. Les observations de ce cas indiquent que la kétamine par voie orale semble avoir été efficace.Conclusion : La kétamine par voie orale semble être efficace pour soulager la douleur associée au syndrome douloureux régional complexe de notre patiente. Il semble raisonnable d’envisager un tel traitement pour certains patients dont la douleur est réfractaire aux traitements classiques.AbstractObjectives: To present a case study of a patient with standard treatment refractory complex regional pain syndrome that responded to oral ketamine. To review the treatment of complex regional pain syndrome.Case summary: The patient is a 36-year-old woman with type 1 complex regional pain syndrome of the left foot in an outpatient setting. She tried numerous treatments and had to stop rehabilitation exercises because of the pain. She was seen at a chronic pain outpatient clinic, and treatment with oral ketamine was initiated. The pain diminished significantly following the introduction of ketamine, and the patient was able to resume a rehabilitation program.Discussion: Complex regional pain syndrome should be managed quickly to prevent the pain from persisting in the long term. A number of pharmacological treatments have been evaluated, but there are few data in the literature on oral ketamine in complex regional pain syndrome. Based on the observations made in this case, oral ketamine was effective to relieve the patient’s pain.Conclusion: It appears that oral ketamine was effective in relieving the pain associated with complex regional pain syndrome in our patient. It seems reasonable to consider this drug in certain specific cases where the pain is refractory to standard treatments

Projet pilote portant sur l’optimisation de la préparation magistrale orale de la clonidine au CHU Sainte-Justine

Résumé Objectif : L’objectif de ce projet pilote est d’optimiser la préparation magistrale orale de la clonidine sur le plan de sa stabilité, de ses propriétés organoleptiques et de sa facilité de reconditionnement en seringues orales au Centre hospitalier universitaire Sainte-Justine afin de réduire les erreurs de calcul de doses et de services.Description de la problématique : Il n’existe aucune forme orale liquide commercialisée de clonidine. Le Centre hospitalier universitaire Sainte-Justine, utilise depuis des années une formulation magistrale concentrée à 0,1 mg/mL pour la patientèle pédiatrique. Cette concentration occasionne parfois des erreurs de calcul et potentiellement de dosage pouvant affecter de façon considérable le patient. De plus, sa stabilité est limitée à 28 jours et le véhicule utilisé, le sirop simple, occasionne des problèmes de mise en seringues orales et d’homogénéité.Résolution de la problématique : Une revue de la littérature a été effectuée pour repérer les différentes formulations magistrales publiées et leur stabilité. Les formulations concentrées à 0,01 mg/mL, 0,02 mg/mL et 0,05 mg/mL ont été retenues pour réaliser un sondage auprès des pharmaciens de l’établissement. Les formulations favorisées par le sondage, soit celles concentrées à 0,01 mg/mL et 0,02 mg/mL, ont été préparées dans Ora-BlendMD et Oral MixMD pour tester la mise en seringues orales et exécuter un examen sommaire de leurs propriétés organoleptiques.Conclusion : La préparation magistrale orale de clonidine retenue est celle concentrée à 20 mcg/mL dans Oral MixMD ou Ora-BlendMD. La nomenclature a été modifiée pour exprimer la concentration de la préparation en microgrammes par millilitre, c’est-à-dire 20 mcg/mL.AbstractObjective: The objective of this pilot project is to optimize the oral compounding of clonidine in terms of its stability, its organoleptic properties and the ease of aliquoting it into oral syringes at the Centre hospitalier universitaire Sainte-Justine in order to reduce dose miscalculations and serving errors.Problem description: There is no commercially available liquid oral form of clonidine. At the Centre hospitalier universitaire Sainte-Justine, a compounded formulation with a concentration of 0.1 mg/mL has been used for years. With this concentration, miscalculations and, potentially, dosage errors, sometimes occur which can substantially affect the patient. In addition, its stability is limited to 28 days, and the vehicle used, simple syrup, causes homogeneity problems and problems aliquoting the formulation into oral syringes.Problem resolution: We conducted a literature review to identify the different published compounded formulations and their stability. Those with a concentration of 0.01 mg/mL, 0.02 mg/mL and 0.05 mg/mL were selected for the purpose of surveying the hospital’s pharmacists. The formulations preferred in the survey, those with a concentration of 0.01 mg/mL and 0.02 mg/mL, were prepared in Ora-Blend® and Oral Mix® to test oral syringe aliquoting and to conduct a summary examination of their organoleptic properties.Conclusion: The compounded oral preparation of clonidine chosen was that with a concentration of 20 mcg/mL in Oral Mix® or Ora-Blend®. The nomenclature was changed to express the concentration of the preparation in micrograms per millilitre, i.e., 20 mcg/mL

Atmospheric Reconnaissance of TRAPPIST-1 b with JWST/NIRISS: Evidence for Strong Stellar Contamination in the Transmission Spectra

TRAPPIST-1 is a nearby system of seven Earth-sized, temperate, rocky exoplanets transiting a Jupiter-sized M8.5V star, ideally suited for in-depth atmospheric studies. Each TRAPPIST-1 planet has been observed in transmission both from space and from the ground, confidently rejecting cloud-free, hydrogen-rich atmospheres. Secondary eclipse observations of TRAPPIST-1 b with JWST/MIRI are consistent with little to no atmosphere given the lack of heat redistribution. Here we present the first transmission spectra of TRAPPIST-1 b obtained with JWST/NIRISS over two visits. The two transmission spectra show moderate to strong evidence of contamination from unocculted stellar heterogeneities, which dominates the signal in both visits. The transmission spectrum of the first visit is consistent with unocculted starspots and the second visit exhibits signatures of unocculted faculae. Fitting the stellar contamination and planetary atmosphere either sequentially or simultaneously, we confirm the absence of cloud-free, hydrogen-rich atmospheres, but cannot assess the presence of secondary atmospheres. We find that the uncertainties associated with the lack of stellar model fidelity are one order of magnitude above the observation precision of 89 ppm (combining the two visits). Without affecting the conclusion regarding the atmosphere of TRAPPIST-1 b, this highlights an important caveat for future explorations, which calls for additional observations to characterize stellar heterogeneities empirically and/or theoretical works to improve model fidelity for such cool stars. This need is all the more justified as stellar contamination can affect the search for atmospheres around the outer, cooler TRAPPIST-1 planets for which transmission spectroscopy is currently the most efficient technique