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163 result(s) for "Choquet, E"
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Kinematic detection of a planet carving a gap in a protoplanetary disk
We still do not understand how planets form or why extrasolar planetary systems are so different from our own Solar System. However, the past few years have dramatically changed our view of the disks of gas and dust around young stars. Observations with the Atacama Large Millimeter/submillimeter Array and extreme adaptive-optics systems have revealed that most—if not all—disks contain substructure, including rings and gaps1–3, spirals4–6, azimuthal dust concentrations7 and shadows cast by misaligned inner disks5,8. These features have been interpreted as signatures of newborn protoplanets, but the exact origin is unknown. Here we report the kinematic detection of a few-Jupiter-mass planet located in a gas and dust gap at 130 au in the disk surrounding the young star HD 97048. An embedded planet can explain both the disturbed Keplerian flow of the gas, detected in CO lines, and the gap detected in the dust disk at the same radius. While gaps appear to be a common feature in protoplanetary disks2,3, we present a direct correspondence between a planet and a dust gap, indicating that at least some gaps are the result of planet–disk interactions.Pinte et al. report the kinematic detection of a few-Jupiter-mass planet orbiting at 130 au from the young star HD 97048. The radial position of the planet coincides with a gap in both the gas and dust components of the protoplanetary disk, showing that at least some gaps can be linked to the presence of planets.
Imaging low-mass planets within the habitable zone of α Centauri
Giant exoplanets on wide orbits have been directly imaged around young stars. If the thermal background in the mid-infrared can be mitigated, then exoplanets with lower masses can also be imaged. Here we present a ground-based mid-infrared observing approach that enables imaging low-mass temperate exoplanets around nearby stars, and in particular within the closest stellar system, α Centauri. Based on 75–80% of the best quality images from 100 h of cumulative observations, we demonstrate sensitivity to warm sub-Neptune-sized planets throughout much of the habitable zone of α Centauri A. This is an order of magnitude more sensitive than state-of-the-art exoplanet imaging mass detection limits. We also discuss a possible exoplanet or exozodiacal disk detection around α Centauri A. However, an instrumental artifact of unknown origin cannot be ruled out. These results demonstrate the feasibility of imaging rocky habitable-zone exoplanets with current and upcoming telescopes. Imaging of low-mass exoplanets can be achieved once the thermal background in the mid-infrared (MIR) wavelengths can be mitigated. Here, the authors present a ground-based MIR observing approach enabling imaging low-mass temperate exoplanets around nearby stars.
CP-132 Impact of pharmaceutical interventions in a medicine department
BackgroundPharmacists play an important role by assuring and improving the quality and safety of the medication circuit, especially through pharmaceutical approval. In our hospital, only 20% of prescriptions are analysed by pharmacists because the pharmacy service suffers from a lack of clinician pharmacists.PurposeIn order to enhance our pharmaceutical validation activity, we analysed our different pharmaceutical interventions and evaluated the pharmacoeconomic impact.Material and methodsA prospective study was conducted in a polyvalent medicine unit for 3 months.Every prescription was analysed by a pharmacist and its interventions were categorised into several categories (aim and type of intervention). The percentage change in prescription following our intervention was assessed and the economic outcome was estimated from the daily cost of treatment change or discontinuation.ResultsThe total number of prescription lines analysed was 6857, with 187 interventions; 50% of interventions were effective. 54% of pharmaceutical interventions aimed at switching from the intravenous (IV) to the oral route and represented the majority of savings (1200€ of 1270€ saved). A high proportion of patients receive IV therapy although this may be inappropriate.Among all pharmacist interventions, 20% recommended a dose adjustment: 40% of them were related to adaptation to kidney function (13% were followed), 26% concerned sub-therapeutic doses (40% were followed) and 34% concerned overdoses (77% followed).11% of pharmaceutical interventions concerned substitution proposition (acceptance of only 21%); this probably leads to therapeutic failure and could lead to undesirable events.The rest of the indications related to therapeutic duplication (8%), difference in personal treatment (4%), association had no indicated (2%) and contraindication (1%). Not many of these interventions were followed, excepted in the last two categories.ConclusionPharmacists’ interventions appear to result in an appropriate prescription and improve the safety of drug therapies. They generate financial savings due to reduction in unnecessary therapy. In the future, we should encourage a dialogue with prescribers. Extrapolation of the results should be performed to present a real financial and medical impact of the pharmaceutical interventions and to obtain a dedicated full time clinician pharmacist.References and/or AcknowledgementsValidation pharmaceutique des prescriptions hospitalières. Presse Médicale August 2005No conflict of interest.
ESCAPE project: fundamental detection limits of JWST/NIRCam coronographic observations
In this study, we explored the fundamental contrast limit of NIRCam coronagraphy observations, representing the achievable performance with post-processing techniques. This limit is influenced by photon noise and readout noise, with complex noise propagation through post-processing methods like principal component analysis. We employed two approaches: developing a formula based on simplified scenarios and using Markov Chain Monte Carlo (MCMC) methods, assuming Gaussian noise properties and uncorrelated pixel noise. Tested on datasets HIP\\,65426, AF\\,Lep, and HD\\,114174, the MCMC method provided accurate but computationally intensive estimates. The analytical approach offered quick, reliable estimates closely matching MCMC results in simpler scenarios. Our findings showed the fundamental contrast curve is significantly deeper than the current achievable contrast limit obtained with post-processing techniques at shorter separations, being 10 times deeper at \\(0.5''\\) and 4 times deeper at \\(1''\\). At greater separations, increased exposure time improves sensitivity, with the transition between photon and readout noise dominance occurring between \\(2''\\) and \\(3''\\). We conclude the analytical approach is a reliable estimate of the fundamental contrast limit, offering a faster alternative to MCMC. These results emphasize the potential for greater sensitivity at shorter separations, highlighting the need for improved or new post-processing techniques to enhance JWST NIRCam sensitivity or contrast curve.
The GRAVITY fringe tracker
The GRAVITY instrument has been commissioned on the VLTI during 2016 and is now available to the astronomical community. It is the first optical interferometer capable of observing sources as faint as magnitude 19 in K-band. This is possible thanks to the fringe tracker which compensates the differential piston based on measurements of a brighter off-axis astronomical reference source. The goal of this paper is to consign the main developments made in the context of the GRAVITY fringe tracker. This could serve as basis for future fringe tracking systems. The paper therefore covers all aspects of the fringe tracker, from hardware, to control software and on-sky observations. Special emphasis is placed on the interaction between the group delay controller and the phase delay controller. The group delay control loop is a simple but robust integrator. The phase delay controller is a state-space control loop based on an auto-regressive representation of the atmospheric and vibrational perturbations. A Kalman filter provides optimal determination of the state of the system. The fringe tracker shows good tracking performance on sources with coherent K magnitudes of 11 on the UTs and 9.5 on the ATs. It can track fringes with an SNR level of 1.5 per DIT, limited by photon and background noises. On the ATs, during good seeing conditions, the optical path delay residuals can be as low as 75 nm root mean square. On the UTs, the performance is limited to around 250 nm because of structural vibrations.
Characterization of debris disks observed with SPHERE
This study aims to characterize debris disks observed with SPHERE across multiple programs, with the goal of identifying systematic trends in disk morphology, dust mass, and grain properties as a function of stellar parameters. We analyzed a sample of 161 young stars using SPHERE observations at optical and near-IR wavelengths. Disk geometries were derived from ellipse fitting and model grids, while dust mass and properties were constrained by modified blackbody (MBB) and size distribution (SD) modeling of SEDs. The dynamical modeling was performed to assess whether the observed disk structures can be explained by the presence of unseen planets. We resolved 51 debris disks, including four new detections: HD 36968, BD-20 951, and the inner belts of HR 8799 and HD 36546. In addition, we found a second transiting giant planet in the HD 114082 system, with a radius of 1.29 \\(R_{\\rm Jup}\\) and an orbital distance of ~1 au. We identified nine multi-belt systems, with outer-to-inner belt radius ratios of \\(1.5-2\\), and found close agreement between scattered-light and millimeter-continuum belt radii. They scale weakly with stellar luminosity (\\(R_{\\rm belt} \\propto L_{\\star}^{0.11}\\)), but show steeper dependencies when separated by CO and CO\\(_2\\) freeze-out regimes. Disk fractional luminosities follow collisional decay trends, declining as \\(t_{\\rm age}^{-1.18}\\) for A and \\(t_{\\rm age}^{-0.81}\\) for F stars. The inferred dust masses span \\(10^{-5}-1\\,M_\\oplus\\) from MBB and \\(0.01-1\\,M_\\oplus\\) from SD modeling. These masses scale as \\(R_{\\rm belt}^n\\) with \\(n>2\\) in belt radius and super-linearly with stellar mass, consistent with trends seen in protoplanetary disks. Analysing correlation between disk polarized flux and IR excess, we found an offset of ~1 dex between total-intensity (HST) and polarized fluxes. A new parametric approach to estimate dust albedo and maximum polarization fraction is introduced.
The ALMA survey to Resolve exoKuiper belt Substructures (ARKS) V: Comparison between scattered light and thermal emission
Debris discs are analogues to our own Kuiper belt around main-sequence stars and are therefore referred to as exoKuiper belts. They have been resolved at high angular resolution at wavelengths spanning the optical to the submillimetre-millimetre regime. Short wavelengths probe the light scattered by such discs, which is dominated by micron-sized dust particles, while millimetre wavelengths probe the thermal emission of millimetre-sized particles. Determining differences in the dust distribution between millimetre- and micron-sized dust is fundamental to revealing the dynamical processes affecting the dust in debris discs. We aim to compare the scattered light from the discs of the ALMA survey to Resolve exoKuiper belt Substructures (ARKS) with the thermal emission probed by ALMA. We focus on the radial distribution of the dust. We used high-contrast scattered light observations obtained with VLT/SPHERE, GPI, and the HST to uniformly study the dust distribution in those systems and compare it to the dust distribution extracted from the ALMA observations carried out in the course of the ARKS project. We also set constraints on the presence of planets by using these high-contrast images combined with exoplanet evolutionary models. 15 of the 24 discs comprising the ARKS sample are detected in scattered light, with TYC9340-437-1 being imaged for the first time at near-infrared wavelengths. For 6 of those 15 discs, the dust surface density seen in scattered light peaks farther out compared to that observed with ALMA. These 6 discs except one are known to also host cold CO gas. Conversely, the systems without significant offsets are not known to host gas, except one. This observational study suggests that the presence of gas in debris discs may affect the small and large grains differently, pushing the small dust to greater distances where the gas is less abundant.
Exomoon search with VLTI/GRAVITY around the substellar companion HD 206893 B
Direct astrometric detection of exomoons remains unexplored. This study presents the first application of high-precision astrometry to search for exomoons around substellar companions. We investigate whether the orbital motion of the companion HD 206893 B exhibits astrometric residuals consistent with the gravitational influence of an exomoon or binary planet. Using the VLTI/GRAVITY instrument, we monitored the astrometric positions of HD 206893 B and c across both short (days to months) and long (yearly) timescales. This enabled us to isolate potential residual wobbles in the motion of component B attributable to an orbiting moon. Our analysis reveals tentative astrometric residuals in the HD 206893 B orbit. If interpreted as an exomoon signature, these residuals correspond to a candidate (HD 206893 B I) with an orbital period of approximately 0.76 years and a mass of \\(\\sim\\)0.4 Jupiter masses. However, the origin of these residuals remains ambiguous and could be due to systematics. Complementing the astrometry, our analysis of GRAVITY \\(R=4000\\) spectroscopy for HD 206893 B confirms a clear detection of water, but no CO is found using cross-correlation. We also find that AF Lep b, and \\(\\beta\\) Pic b are the best short-term candidates to look for moons with GRAVITY+. Our observations demonstrate the transformative potential of high-precision astrometry in the search for exomoons, and proves the feasibility of the technique to detect moons with masses lower than Jupiter and potentially down to less than Neptune in optimistic cases. Crucially, further high-precision astrometric observations with VLTI/GRAVITY are essential to verify the reality and nature of this signal and attempt this technique on a variety of planetary systems.