Photométrie de haute précision dans l'infrarouge d'exoplanètes en transit

Pour les hommes en quête de sens, l’exploration de nouvelles terres a été et est certainement encore l’un des plus grands défis possibles. Aujourd’hui ces nouveaux mondes dont nous parlons sont éloignés de plusieurs années lumière, et sont appelés exoplanètes. Découvertes récemment, il est désormais possible d’étudier les structures de ces dernières, de même que leurs compositions et propriétés atmosphériques, sans même devoir résoudre leur lumière de celle de leur étoile hôte : c’est en effet possible lorsque ces planètes passent régulièrement devant (transit) et derrière (occultation) leur étoile hôte par rapport à notre angle de vue. L’étude des exoplanètes et de leur atmosphère est de première importance. Elle pourrait nous renseigner sur les conditions présentes lors de leur formation et de leur évolution, et ainsi même nous aider à mieux caractériser les planètes du système solaire. La détermination des propriétés orbitales et atmosphériques des exoplanètes en transit fait partie des principaux objectifs de cette thèse. Nous utilisons ainsi des observations dans le domaine infrarouge, siège de nombreuses transitions de molécules constituant leurs atmosphères. Cependant plusieurs effets systématiques propres aux détecteurs infrarouges, en particulier ceux à bord du télescope spatial Spitzer (3,6–24 μm), ont déjà conduit à différentes conclusions quant à la nature atmosphérique de la planète étudiée, selon la façon de traiter les données. Ainsi, ce travail de thèse se concentre également sur le traitement et l’analyse des données photométriques infrarouges de haute précision, afin d’obtenir des mesures rigoureuses, non ambiguës et pouvant permettre la caractérisation des exoplanètes, notamment via la reconstitution de leur spectre d’émission et de transmission. Par la même occasion, nous tentons de mieux comprendre le comportement des instruments infrarouges en vue des futures missions dans ce domaine de longueur d’onde, tel le télescope spatial James Webb. Notre travail s’articule en guise d’application autour de la caractérisation du système planétaire de GJ 436 par le traitement et la réanalyse des observations Spitzer et de CoRoT-2 à l’aide d’observations au sol et Spitzer. A ces fins, nous employons et optimisons le programme de photométrie de déconvolution partielle DECPHOT, idéal pour séparer les contributions des flux des étoiles entre elles et de celle du ciel, particulièrement importante en infrarouge. Parallèlement, nous perfectionnons la technique de photométrie d’ouverture. En aval de ces traitements de données, nous exploitons un algorithme de Monte Carlo de chaînes de Markov, développé dans l’équipe de Liège, pour analyser les courbes de lumière produites par ces deux techniques de mesure photométrique, et en complément des courbes de vitesses radiales également disponibles pour les deux sys- tèmes étudiés. Nous enrichissons cet algorithme d’une nouvelle manière de modéliser un des effets systématiques de Spitzer, ainsi que d’un modèle de courbe de phase adapté pour une orbite excentrique. Notre analyse de GJ436b écarte la présence des compagnons candidats planétaires proposés récemment dans la littérature. Contrairement aux études antérieures aux résultats contradictoires, nous mesurons une profondeur d’occultation à 3,6 μm indépendante de la manière de construire la courbe de lumière, grâce à notre modélisation de l’effet intrapixel. Nos résultats indiquent ainsi une faible variabilité de son étoile hôte et suggèrent une atmosphère riche en métaux. L’étude de CoRoT-2 b conduit à une mesure d’émission très élevée à 2,09 μm, signalant une atmosphère en non-équilibre thermodynamique local et/ou chimique. Elle pourrait indiquer l’émission de H+3 , résultant d’une émission stellaire ultraviolette intense ou d’aurores planétaires.The exploration of new lands has always been and is still an appealing quest of the Mankind. Today, these new worlds we are talking about are several light years away from us, and are called exoplanets. Recently discovered, it is possible to study their structures, as well as their atmospheric compositions and properties, without the need to resolve their light from their host star. This is indeed possible when a planet regularly pass in front (transit) or behind (occultation) its host star from our point of view. The study of exoplanets and of their atmosphere is of prime importance. It could inform us on present conditions during their formation and evolution, and thus help us to characterise planets in our own Solar system. The characterisation of the orbital and atmospheric properties of transiting exoplanets is among the main goal of this thesis. We use observations in the infrared band, wherein exoplanet spectra present many atmospheric molecular transition features. However several infrared instrument systematics, particularly those on-board the Spitzer telescope (3.6–24 μm), have already led to divergent conclusions on the nature of planetary atmospheres it targeted, depending on the way these systematics were treated. Hence this thesis focuses on the high-precision infrared data reduction and analysis of transiting exoplanets. Our goal is to obtain accurate and non-ambiguous measurements for the characterisation of exoplanets through the recombination of their emission and transmission spectra. Meanwhile, we attempt to better understand the behaviour of infrared detectors in preparation for future missions in this wavelength range, such as the James Webb Space Telescope. This work is organised around the characterisation of the GJ 436 planetary system based on the data reduction and reanalysis of Spitzer observations and of CoRoT-2 with the help of ground-based and Spitzer observations. We use and optimise the partial deconvolution photometry program DECPHOT, fully appropriate to separate the stellar flux contributions from each other and from that of the sky, which is particularly important in the infrared. Besides, we improve aperture photometry. Then we use the Markov chain Monte Carlo algorithm developed by the Liège team to analyse the light curves produced by these two measurement techniques, in addition to radial velocity measurements that were also available for these systems. We introduce new features, including a mo- delisation of one of the Spitzer systematics, and a phase curve model adapted to eccentric planetary orbit. Our GJ 436b analysis rules out the presence of the two planetary companion candidates proposed recently in the literature. Contrary to former studies that were in disagreement, we measure an occultation depth at 3.6 μm that is independent of the light curve reduction, thanks to our modelisation of the intrapixel effect. We point out a weak stellar activity of its host star and suggest a metal rich atmosphere. Our CoRoT-2 b study leads to a very high emission measurement at 2.09 μm, which highlights an atmosphere in chemical and/or local thermodynamical disequilibrium. It may indicate the emission of H+3 , which results from high extreme UV stellar radiation or planetary aurora emission

La sclérose en plaque et l'évolution des traitements (Evaluation des connaissances des pharmaciens d officine en Lorraine, et réalisation d une fiche d information)

NANCY1-Bib. numérique (543959902) / SudocSudocFranceF

How asteroseismology can help to precisely constrain properties of planet-host stars

Nowadays more than 500 exoplanets have been discovered, mainly studied by radial velocity and transit measurements. Precise knowledge on their characteristics is crucial to develop theories of planetary formation and evolution. In that aim, not only star and planet(s) masses but also the evolutionary stage of systems are needed. From radial velocity measurements one has to assume the inclination and the stellar mass of the system to disentangle the mass of the planet. When transit is observable, one can measure the ratio of planetary and stellar radii. Finally, the degree of evolution of the system is determined by the one of the star. Thus the host star must be well known to obtain a full set of system properties. However, determination of stellar parameters such as the mass, radius and its evolution from classical observables (Teff, log g, [Fe/H]) suffers of large uncertainties. This is particularly true for dwarf stars on the Main Sequence. Fortunately we can obtain better constrains with the help of asteroseismology. That latter approach probes the stellar properties through observation of oscillations present in stars. With the launches of high-precision photometry space missions, CoRoT and Kepler, we are now able to detect oscillations in a huge number of stars. In particular Kepler photometry, primarily intended to detect transits of planet, can give accurate stellar parameters of planetary systems as it also affords to mak

Colour-magnitude diagrams of transiting Exoplanets - II. A larger sample from photometric distances

peer reviewedCColour-magnitude diagrams form a traditional way of presenting luminous objects in the Universe and compare them to each other. Here, we estimate the photometric distance of 44 transiting exoplanetary systems. Parallaxes for seven systems confirm our methodology. Combining those measurements with fluxes obtained while planets were occulted by their host stars, we compose colour-magnitude diagrams in the near and mid-infrared. When possible, planets are plotted alongside very low mass stars and field brown dwarfs, who often share similar sizes and equilibrium temperatures. They offer a natural, empirical, comparison sample. We also include directly imaged exoplanets and the expected loci of pure blackbodies. Irradiated planets do not match blackbodies; their emission spectra are not featureless. For a given luminosity, hot Jupiters' daysides show a larger variety in colour than brown dwarfs do and display an increasing diversity in colour with decreasing intrinsic luminosity. The presence of an extra absorbent within the 4.5 μm band would reconcile outlying hot Jupiters with ultra-cool dwarfs' atmospheres. Measuring the emission of gas giants cooler than 1000 K would disentangle whether planets' atmospheres behave more similarly to brown dwarfs' atmospheres than to blackbodies, whether they are akin to the young directly imaged planets, or if irradiated gas giants form their own sequence

Mont ABU 2.5m Telescope: How to assess large telescope performances in factory?

Before the transport of a large telescope on site, it is suitable to perform factory tests to guarantee the optical performances. AMOS SA has been awarded of the contract from the design to on-site installation (in Rajasthan) of the 2.5-m Class Telescope for Physical Research Laboratory. The 20-m-focal-length telescope has a Ritchey-Chrétien optical configuration and provides at Cassegrain location one axial port and two side ports. It is equipped with a primary active mirror and a first order adaptive optical system. It operates in the 0.37-4 μm spectral range. The project fulfillment relies on the AMOS multidisciplinary expertise in design and manufacturing of high-accuracy optical, mechanical and opto-mechanical systems. This paper presents the test results carried out at AMOS factory to assess the telescope performances (e.g. active optic control loop, pointing, tracking). It relies on extensive tests on the mount control, and the optical and mechanical sub-systems before assembly

Setting-up a fast and reliable cytokinin biosensor based on a plant histidine kinase receptor expressed in Saccharomyces cerevisiae

International audienceCytokinins (CK) have been extensively studied for their roles in plant development. Recently, they also appeared to ensure crucial functions in the pathogenicity of some bacterial and fungal plant pathogens. Thus, identifying cytokinin-producing pathogens is a prerequisite to gain a better understanding of their role in pathogenicity. Taking advantage of the cytokinin perception properties of Malus domestica CHASE Histidine Kinase receptor 2 (MdCHK2), we thereby developed a selective and highly sensitive yeast biosensor for the application of cytokinin detection in bacterial samples. The biosensor is based on the mutated sln1Δ Saccharomyces cerevisiae strain expressing MdCHK2. The biosensor does not require any extraction or purification steps of biological samples, enabling cytokinin analysis directly from crude bacterial supernatants. For the first time, the production of cytokinin was shown in the well-known plant pathogenic bacteria Erwinia amylovora and was also revealed in human pathogens Staphylococcus aureus and Streptococcus agalactiae. Importantly, this biosensor was shown to be an efficient tool for unraveling certain steps in cytokinin biosynthesis by micro-organisms since this it was successfully used to unveil the role of ygdH22, a LOG-like gene, that is probably involved in cytokinin biosynthesis pathway in Escherichia coli. Overall, we demonstrated that our biosensor displays several advantages including time- and cost-effectiveness by allowing a rapid and specific detection of cytokinins in bacterial supernatants These results also support its scalability to high-throughput formats

Effects of azithromycin and doxycycline on the vaginal microbiota of women with urogenital Chlamydia trachomatis infection: a substudy of the Chlazidoxy randomized controlled trial

Objectives: Dysbiotic bacterial communities within the vagina are associated with Chlamydia trachomatis infection. We compared the effect of treatment with azithromycin and doxycycline on the vaginal microbiota in a cohort of women with a urogenital C. trachomatis infection randomly assigned to one of these treatments (Chlazidoxy trial). Methods: We analysed vaginal samples from 284 women (135 in the azithromycin group and 149 in the doxycycline group) collected at baseline and 6 weeks after treatment initiation. The vaginal microbiota was characterized using 16S rRNA gene sequencing and classified into community state types (CSTs). Results: At baseline, 75% (212/284) of the women had a high-risk microbiota (CST-III or CST-IV). A crosssectional comparison 6 weeks after treatment showed that 15 phylotypes were differentially abundant, but this difference was not reflected at the CST (p 0.772) or diversity level (p 0.339). Between baseline and the 6-week visit, a-diversity (p 0.140) and transition probabilities between CSTs were not significantly different between the groups, and no phylotype was differentially abundant. Discussion: In women with urogenital C. trachomatis infection, the vaginal microbiota does not seem to be affected by azithromycin or doxycycline 6 weeks after treatment. Because the vaginal microbiota remains susceptible to C. trachomatis infection (with CST-III or CST-IV) after antibiotic treatment, women remain at risk of reinfection, which could originate from unprotected sexual intercourse or untreated anorectal C. trachomatis infection. This last consideration advocates for the use of doxycycline instead of azithromycin because of its higher anorectal microbiological cure rate. Jeanne Tamarelle, Clin Microbiol Infect 2023;29:1056 & COPY; 2023 European Society of Clinical Microbiology and Infectious Diseases.Plateforme d'Innovation " Forêt-Bois-Fibre-Biomasse du Futur