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Dutil, Yvan. "Les abondances chimiques dans les galaxies spirales de type précoce". Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1998. http://www.collectionscanada.ca/obj/s4/f2/dsk3/ftp04/nq26059.pdf.
Pełny tekst źródłaVan, der Swaelmen Mathieu. "Évolution chimique du Grand Nuage de Magellan". Phd thesis, Université Nice Sophia Antipolis, 2013. http://tel.archives-ouvertes.fr/tel-00833887.
Pełny tekst źródłaLebouteiller, Vianney. "Abondances chimiques dans le gaz neutre des régions à flambée de formation d'étoiles". Phd thesis, Université Pierre et Marie Curie - Paris VI, 2005. http://tel.archives-ouvertes.fr/tel-00448226.
Pełny tekst źródłaThévenin, Frédéric. "Contribution a l'etude des abondances des populations stellaires". Paris 7, 1987. http://www.theses.fr/1987PA077294.
Pełny tekst źródłaTitarenko, Anastasia. "Indicateurs chimiques d’âge stellaire à l’ère de Gaia". Thesis, Université Côte d'Azur (ComUE), 2018. http://www.theses.fr/2018AZUR4065/document.
Pełny tekst źródłaStars record the past in their ages, chemical compositions and kinematics. They can provide unprecedented detailed constraints on the early epochs of galaxy formation, back to redshifts greater than two (a look-back time of around 10 billion years). In particular, stellar ages are crucial to the understanding of the Milky Way history and for comparison with galactic evolution models. The advent of the Gaia space mission has opened the path to stellar age estimations for large samples of stars, in particular, based on isochrone fitting methods. In addition, Gaia precise distances allow to develop indirect age estimations based on the stellar population chemical evolution clock. In fact, the chemical abundance patterns imprinted on stellar atmospheres represent the gas conditions at the time of the stars’ formation back to redshifts greater than two. The chemical evolution products of different nucleosynthetic channels can therefore provide a time proxy. After calibration, it can be used as an age estimator.This thesis is focussed on the use of a particular chemical clock, the [Y/Mg] abundance. To this purpose, the astrometric Gaia mission data from the first data release was combined with high resolution spectroscopic data from the AMBRE-HARPS catalogue. First of all, the object identification of the AMBRE archival data was improved, thanks to a cross match with the 2MASS catalog, and later the Gaia DR1. In total, 6776 different stars have been identified.Secondly, in order to obtain precise estimations of the [Y/Mg] abundance ratio for galactic disc stars, the automated GAUGUIN tool integrated in the Gaia DPAC APSIS chain, has been optimized and tested. In particular, the abundance estimation capabilities of the APSIS GAUGUIN tool have been improved for irregularly distributed synthetic spectra grids, spanning a large range in stellar atmospheric parameters.Thirdly, the [Y/Mg] abundance ratio has been estimated for about 2000 stars from the AMBRE HARPS spectroscopic data. In addition, the internal and external errors of the abundances were carefully analysed. The studied stars belong mainly to the galactic thin and thick disc, in the metallicity range from --1.0 dex to 0.5 dex.Fourth, thanks to the isochrone fitting age estimations of 342 turn-off stars of the sample, the age sensitivity of the [Y/Mg] ratio has been studied. The analysis reveals a clear correlation between [Y/Mg] and age for thin disk stars of different metallicities, in synergy with previous studies of Solar type stars. In addition, no metallicity dependence with stellar age is detected, allowing to use the [Y/Mg] ratio as a reliable age proxy.Finally, the [Y/Mg] vs. age relation presents a discontinuity between thin and thick disk stars around 9–10 Gyrs. For thick disk stars, the correlation has a different zero point and probably a steeper trend with age, reflecting the different chemical evolution histories of the two disk components
Blanco-Cuaresma, Sergi. "Test de la technique de marquage chimique avec des amas ouverts". Thesis, Bordeaux, 2014. http://www.theses.fr/2014BORD0079/document.
Pełny tekst źródłaContext. Stars are born together from giant molecular clouds and, if weassume that they were chemically homogeneous and well-mixed, we expect them toshare the same chemical composition.Most of the stellar aggregates are disrupted while orbiting the Galaxy and thedynamic information is lost, thus the only possibility to reconstruct the stellarformation history is to analyze the chemical abundances that we observe today.Aims. The chemical tagging technique aims to recover disrupted stellarclusters based merely on their chemical composition. We evaluate the viability of thistechnique to recover conatal stars that are not gravitationally bound anymore.Methods. We built a high-quality stellar spectra library to facilitate theassessment of spectral analyses. We developed our own spectral analysisframework, named iSpec, capable of homogeneizing stellar spectra and derivingatmospheric parameters/chemical abundances. Finally, we compiled stellar spectrafrom 32 Open Clusters, homogeneously derived atmospheric parameters and 17abundance species, and applied machine learning algorithms to group the starsbased on their chemical composition. This approach allows us to evaluate theviability of the chemical tagging technique.Results. We found that stars in different evolutionary stages havedistinguished chemical patterns may be due to NLTE effects, atomic diffusion, mixingand correlations from atmospheric parameter determinations. When separating starsper evolutionary stage, we observed a high degree of overlapping among OpenCluster’s chemical signatures, making it difficult to recover conatal aggregates byapplying the chemical tagging technique
Lecureur, Aurélie. "Contraintes observationnelles sur la formation et l’évolution chimique du bulbe galactique". Observatoire de Paris (1667-....), 2007. https://hal.science/tel-02071421.
Pełny tekst źródłaThe Milky Way bulge shows contradictory features. Its structure and shape are close to those of late-type galaxies which are believed to be made secularly out of the disk instabilities (“pseudo-bulges”). However, its stellar population seems to be old and metal-rich in line with the typical characteristics of Sa and Sb spheroids (“classical bulge”). Using the FLAMES instrument (VLT), we observed 5 samples of about 230 bulge giants stars in 4 fields spread perpendicularly to the galactic plane from b=-3° to b=-12°. Intermediate resolution spectra (R~ 20000) have been obtained with the FLAMES/GIRAFFE spectrograph for all stars and 55 have also been observed with the high resolution spectrograph FLAMES/UVES (R~48000). This thesis is based on the analysis of the 55 UVES stars for which we obtained oxygen, magnesium, aluminum and sodium abundances as well as on the Red Clump giants GIRAFFE sample in Baade’s Window (l = 1°, b = -4°) for which individual metallicities ([Fe/H]) have been measured. For this work, an automatic method has been specifically developed to deal with the issues arising from the analysis of these heavily reddened metal-rich giant stars. Our study establishes, a bulge metallicity distribution (MD) in the Baade’s Window entirely based, for the first time, on a large sample (220 stars), with [Fe/H] values coming from the analysis of intermediate resolution spectra and consequently more precise than previous studies. This allow us to confirm some of the MD characteristics and to highlight new ones : (i) a sharp decrease at high metallicities ([Fe/H]>0. 5, (ii) a large number of stars with supersolar metallicities (50 % with [Fe/H]>0. 16, 25% with [Fe/H]>0. 38) and (iii) few metal poor star (about 2% of stars with -1. 1 [Fe/H]<-0. 7). The abundance results of O, Na, Mg and AI from the UVES spectra show that the bulge have encountered a chemical evolution distinct from the galactic thin and thick disks. The bulge oxygen and magnesium ratios relative to iron are higher than those on both galactic disks, which point towards a shorter formation timescale for the galactic bulge. The comparison of the MD and -α (O and Mg) abundances with those predicted by chemical evolution models suggests an extremely efficient and fast stellar formation, which would have been suddenly stopped via SNe winds. Some models also predict a flatter IMF, favouring massive stars. Moreover, an detailed inspection of the massive stars nucleosynthesis has shown that : (i) the bulge stars [O/Mg] ratio follows and extends the decreasing trend of [O/Mg] found in the galactic disks to higher metallicities. This decrease at the highest metallicities is not predicted by theoretical models massive stars, (ii) th [Na/Mg] ratio trend with increasing [Mg/H] is found to increase in three distinct sequences in the thin disk, the thick disk and the bulge. This point to an additional source of Na (AGB) in addition to the massive stars contribution
Toqué, Nathalie. "Diffusion turbulente anisotrope dans les zones radiatives d'étoiles". Thèse, Paris 6, 2004. http://hdl.handle.net/1866/17334.
Pełny tekst źródłaMaret, Sébastien. "Structure physico-chimique des proto-étoiles de faible masse". Phd thesis, Université Paul Sabatier - Toulouse III, 2003. http://tel.archives-ouvertes.fr/tel-00003798.
Pełny tekst źródłaCastro, Matthieu. "Etude des éléments chimiques et tests sismiques de la structure interne du Soleil et des étoiles". Phd thesis, Université Paul Sabatier - Toulouse III, 2006. http://tel.archives-ouvertes.fr/tel-00128196.
Pełny tekst źródłaLes deux premières parties de ce manuscrit présentent de manière théorique les processus de transport et les principes de l'astérosismologie utilisés dans les modèles stellaires.
La troisième partie s'interesse à la signature astérosismique de la diffusion de l'hélium dans les étoiles de type F tardives et à son évolution. Nous montrons que le gradient créé par la diffusion de l'hélium sous la zone convective conduit à un pic dans le transformée de Fourier des secondes différences de spectre de fréquences d'oscillations. Plus le gradient est important, plus l'amplitude du pic est grande.
Le quatrième chapitre étudie la destruction du lithium dans les étoiles avec planètes. De récentes observations de Israelian et al. (2004) montrent que les étoiles froides avec planètes présentent une destruction du lithium importante, contrairement aux étoiles sans planètes. Nos modèles surmétalliques ont permis de montrer d'une part que le gradient de µ pouvait stabiliser le mélange dans les étoiles sans planètes, empêchant la destruction du lithium, et d'autre part que cette destruction dans les étoiles avec planètes pouvait provenir d'instabilités de cisaillement dues à la migration des planètes vers leur étoile centrale.
Enfin, la cinquième partie présente un travail sur les modèles solaires avec les nouvelles abondances de Asplund et al. (2005), qui présentent un désaccord avec les déductions héliosismiques. Nos modèles simulant une accrétion sous-métallique au début de la séquence principale améliorent la situation mais ne réussissent pas à rétablir l'accord avec l'héliosismologie, malgré l'introduction d'un overshooting et d'un mélange rotationnel sous la base de la zone convective.
Bouziani, Naceur. "Elaboration d'un modèle thermo-chimique de la matière cométaire : contribution à l'étude physico-chimique des milieux poreux hétérogènes". Université Joseph Fourier (Grenoble), 1995. http://www.theses.fr/1995GRE10190.
Pełny tekst źródłaGuiglion, Guillaume. "Étude du disque galactique par marquage chimique de ses populations stellaires". Thesis, Nice, 2015. http://www.theses.fr/2015NICE4114/document.
Pełny tekst źródłaStudying both the chemical composition and kinematics of Milky Way stars is essential to understand how big structures of our Galaxy are formed. Indeed, low-mass stars retain in their photosphere the chemical composition of the interstellar medium is which they were born. Additionally, the kinematics are essential to characterize stellar populations. In this thesis, we focus on the galactic disc, a major component of the Milky Way. In the context of the Gaia mission, we have developed an automatic procedure GAUGUIN, devoted to deriving chemical abundances. We first applied our method to the Gaia-ESO Survey (GES) data to derive alpha and iron-peak chemical abundances for 10000 stars. We then derived lithium abundances for 7300 stars from the AMBRE project. GAUGUIN is well adapted to massive spectroscopic surveys, both in terms of computation time and accuracy. GAUGUIN will be soon integrated into the RVS DPAC analysis pipeline of the Gaia mission. We studied the velocity dispersions in the galactic disc as a function of the [Mg/Fe] ratio, used as an age proxy. Thanks to 6800 GES stars, we detected thick disc stars with cool kinematics and high [Mg/Fe] ratio, so presumably old. In the generally turbulent context of the primitive galactic disc, this thesis places these results in the framework of the different disc formation and evolution scenarios. We also showed that the lithium abundance in the galactic disc increases as a function of the metallicity in the domain -1<[M/H]+0 dex and decreases at super-solar metallicities. Finally, the thin and the thick discs could be characterized by different lithium abundance evolutions
Bureau, Jérôme. "Les raies moléculaires de l'atmosphère solaire dans l'infrarouge : spectroscopie, transfert radiatif et modélisation physico-chimique du CO et de ses isotopomères". Paris 6, 2009. http://www.theses.fr/2009PA066250.
Pełny tekst źródłaMasseron, Thomas. "La nucléosynthèse stellaire dans l'histoire galactique : analyse des étoiles carbonées". Observatoire de Paris (1667-....), 2006. https://hal.science/tel-02071411.
Pełny tekst źródłaIn the light of recent results on their nature, their origin and their possible relation with stars of population III (still undiscovered !), we study a sample of metal-poor carbon enhanced stars. This sample includes a large variety of carbon stars such as barium stars, CH stars, carbon enhanced metal-poor stars and an R type star. The common explanation call upon a mass transfer scenario from an now extinct star. Our radial velocity follow up confirms statistically this statement. After a careful reduction of the spectra, we carefully determine elemental abundances, using to state of the art stellar atmosphere and spectral synthesis codes. We show that the impact of molecules on the thermal structure of the atmosphere can induce significant effects on abundances and photometry. Two groups appears regarding the heavy elements abundances : stars only enriched is an element and stars also enriched in r elements. Concerning the former, we confirm the mass transfer scenario from an asymptotic giant branch star. But the abundance analysis of the latter reveals that their companion were more massive stars. Our sample includes a thermal pulsing asymptotic giant branch star, with an extremely low content of metals, making it the most evolved star among metal-poors stars. We highlight that we observe now indirectly the primary nucleosynthesis production of stars born in the first times of our Galaxy. However the picture remains still incomplete, and further studies are required in order to understand the origin of these objects
Gebran, Marwan. "Détermination des abondances des éléments chimiques d'étoiles A et F naines membres de deux amas ouverts. Contraintes sur les modèles évolutifs incluant les processus de transport". Phd thesis, Université Montpellier II - Sciences et Techniques du Languedoc, 2007. http://tel.archives-ouvertes.fr/tel-00290749.
Pełny tekst źródłaEn observant en particulier des étoiles A et F dans des amas ouverts, on peut obtenir des informations additionnelles qui facilitent la comparaison aux mod`eles, soient la composition chimique initiale et l'age de ces étoiles. Ainsi en déterminant la composition chimique des étoiles A/F dans plusieurs amas ouverts d'ages différents, on peut suivre l'évolution de la composition chimique de surface et contraindre les modèles évolutifs au niveau des processus de transport.
Dans cette thèse, j'expose l'analyse de la composition chimique d'échantillons d'étoiles A et F dans deux amas ouverts d'ages différents: les Pléiades (100 Myrs) et Coma Berenices (450 Myrs). Ce travail repose sur des observations que j'ai menées avec les trois spectrographes AURELIE, ELODIE et SOPHIE a l'Observatoire de Haute-Provence (OHP). La méthode des spectres synthétiques, basée sur des modèles d'atmosphères d'ATLAS9-12, a été utilisée afin de déterminer les abondances de 22 éléments. Ces observations sont ensuite comparées aux prédictions des modèles évolutifs de Montréal. Les résultats démontrent l'existence de processus hydrodynamiques dans les zones radiatives de ces étoiles et qui contrebalancent les effets de la diffusion microscopique.
Baumgarten, Sigrid. "Applications de la très haute résolution en spectrométrie de masse à l'attribution de l'origine d'explosifs et à l'identification et la détection d'agents chimiques dans des mélanges complexes". Paris 6, 2009. http://www.theses.fr/2009PA066130.
Pełny tekst źródłaVarenne, Olivier. "Determination des abondances des elements chimiques d'etoiles a et f naines d'amas ouverts et du champ. Comparaison aux predictions des modeles recents incluant les processus de transport". Université Louis Pasteur (Strasbourg) (1971-2008), 1999. http://www.theses.fr/1999STR13182.
Pełny tekst źródłaDepagne, Éric. "Abondance des éléments plus légers que le zinc dans les premières étoiles galactiques : implications sur la nature des premières supernovae". Paris 6, 2003. https://tel.archives-ouvertes.fr/tel-00165388.
Pełny tekst źródłaDuring my Ph. D. I have analyzed 33 extremely metal-deficient galactic halo stars (stars having less than 500 times less metals than the Sun) observed at the VLT, using the high resolution spectrograph UVES. These stars are relics from the very first ages of our Galaxy, and thud provide useful constraints on both the formation and on the evolution models of our Galaxy. I determined the abundances for 17 elements from carbon to zinc with an unprecedented accuracy, including the key elements oxygen and zinc, to understand which kind of supernova had enriched the interstellar medium during the early times of the Galaxy. I have shown in this work that we could explain the observed abundance ratio without including very massive supernova (stars whose mass is greater then M Sun). In addition, the abundance trends are compared with Galactic chemical evolution models. As the study is based on very metal poor stars that are supposed to be born during the first ages of our Galaxy, my work brings strong new observational constraints to these models
Kubryk, Maxime. "Migration radiale dans les disques galactiques et applications à la Voie Lactée". Thesis, Paris 6, 2014. http://www.theses.fr/2014PA066599/document.
Pełny tekst źródłaWe study the radial migration of stars, and test its impact on the chemical evolution of the Milky Way. For this we use a simulation-body + SPH (Gadget-3) strongly barred galaxy to study the radial migration induced by the bar. We examine a new mechanism of radial migration: a fraction of stars trapped at corotation with the bar, move with the corotation radius when it goes outwards (when the rotational speed of the bar decreases, because of its secular evolution). We show that this mechanism affects mainly the outer regions of the disc, provided that the corotation reaches these regions. We also show that the mechanism has no effects in the Milky Way, as the observational estimates of the characteristics of the bar indicates that the corotation is not in the outer regions. We also analyze the radial migration in this simulation to construct an empirical model of diffusion in the stellar disk, and we include this model in a semi-analytic code of chemical evolution of galaxy. We test the validity of this approach by ensuring that the galaxies simulated with N-body + SPH and semi-analytic have similar morphological and chemical properties. We then apply our model to the Milky Way, by adapting the model parameters. Then, we compare the results obtained with a large number of observations on the solar neighborhood (age-metallicity relation, metallicity distribution, relationship O/Fe vs. Fe/H and bimodality thin disk - thick disk), and radial gradients of abundances
Ledoux, Cédric. "SYSTEMES D'ABSORPTION DANS LE SPECTRE DES QUASARS: CINEMATIQUE, METALLICITE, EVOLUTION COSMOLOGIQUE". Phd thesis, Université Claude Bernard - Lyon I, 1999. http://tel.archives-ouvertes.fr/tel-00003228.
Pełny tekst źródłaEscolano, Cyril. "Analyse spectroscopique détaillée d'atmosphères stellaires : structure des vents et composition chimique de surface des étoiles O". Aix-Marseille 1, 2010. http://www.theses.fr/2010AIX10150.
Pełny tekst źródłaMassive stars are the central engines of various astrophysical processes : they ionize the surrounding hydrogen, giving birth to HII regions and, through their stellar winds, they yield the processed material synthetized in their core and inject mechanical energy to the surrounding medium. In addition, they are suspected to be the progenitors of the most luminous and energetic events observed at the time, namely (core-collapse) supernovae and gamma ray bursts. Far from being the homogeneous outflows of material described initially by the radiatively driven winds theory, the massive stars’ atmospheres are highly structured (wind clumping) and exhibit an intense activity (X-rays emissivity and magnetic fields for instance). During my thesis, I was particularly interested in the properties of the massive, hot and luminous O type stars. I realized the detailed spectroscopic analysis of a sample of these objects (some of them hosting a magnetic field), with the state-of-art radiative transfer code CMFGEN. From this analysis, I determined their fundamental parameters (effective temperature, surface chemical abundances, mass loss rates,. . . ) and confronted them to the most recent theoretical models. My results confrm that strong contrasts exist between the observational parameters and those expected by both theoretical wind models and stellar evolution models
Champavert, Nicolas. "Simulations numériques chemodynamiques de la formation et de l'évolution des galaxies". Phd thesis, Lyon 1, 2007. https://theses.hal.science/docs/00/26/07/26/PDF/champavert.pdf.
Pełny tekst źródłaGalaxies are complex systems where dynamics and chemical evolution are closely linked. In order to study the formation and the evolution of galaxies, we have developed a new chemodynamical code in which dynamics and chemical evolution are modelled in a self-consistent way. Our code describes the interstellar medium, the main physical processes of the ISM and the interaction with stars. Stellar evolution and feedback are modelled with a non-instantaneous recycling approach. One original feature of our code is the record of the evolution of individual abundances for several chemical elements. This allows us to compute the radiative cooling of the gas according to its chemical composition. We can also study the temporal and spatial evolution of chemical composition and chemical gradients. The first tests highlight the importance of individual chemical abundances tracking and its influence on gas cooling, and also on star formation and chemical enrichment histories. Furthermore, with our two-phased ISM model, we can reproduce a three-media ISM matching the observations. The slope of the cluster initial mass function is also close to observations. Finally, our new chemodynamical code allows us to study the different physical processes leading to the evolution of galaxies on both dynamical and chemical points of view
Champavert, Nicolas. "Simulations numériques chemodynamiques de la formation et de l'évolution des galaxies". Phd thesis, Université Claude Bernard - Lyon I, 2007. http://tel.archives-ouvertes.fr/tel-00260726.
Pełny tekst źródłaLes premiers tests effectués montrent l'importance du suivi des abondances individuelles des éléments, car celles-ci influent sur le refroidissement du gaz et par conséquent sur l'historique de formation stellaire et de l'enrichissement chimique. Notre description à deux phases du milieu interstellaire nous permet de reproduire trois milieux distincts en accord avec les observations. La pente de la fonction de masse initiale des amas stellaires est semblable à celle observée. Finalement, grâce à ce nouveau code chemodynamique, nous sommes en mesure d'étudier les différents mécanismes physiques impliqués dans l'évolution des galaxies aussi bien du point de vue dynamique que chimique.
Lemoine-Busserolle, Marie. "Etude des propriétés physiques de galaxies lointaines à partir des télescopes gravitationnels". Toulouse 3, 2003. http://www.theses.fr/2003TOU30242.
Pełny tekst źródłaWe report the results obtained from optical and near-infrared spectroscopy and also broadband photometry of lensed low-luminosity galaxies (1. 8 < z < 2. 3) located in the core of lensing clusters. The amplification factor allowed to obtain the physical properties (SFR, abundance ratios, mass, age of the burst, dust contents, etc. ) of starforming galaxies, 1 to 2 magnitudes fainter than galaxies in blank field, using the same indicators as in study of low-redshift galaxies. The results obtained on the physical properties of AC114-S2 (z=1. 867), AC114-A2 (z=1. 869) and A-Cl2244-02 (z=2. 240) suggest that high-z objects of different luminosities could have quite different star formation histories. However, the number of well observed high redshift objects is currently very small and larger samples in both redshift (1. 5 < z < 6) and luminosity are required. This could be achieved with the new generation of multi-object NIR spectrographs for the 10 m class telescopes, such as KMOS on the VLT or EMIR on the GTC
Vernet, Joël. "Etude spectropolarimétrique des premières phases de l'évolution des galaxies les plus massives". Paris 7, 2001. http://www.theses.fr/2001PA077247.
Pełny tekst źródłaRojas-Arriagada, Álvaro. "Étude du bulbe galactique avec le Gaia-ESO survey". Thesis, Université Côte d'Azur (ComUE), 2016. http://www.theses.fr/2016AZUR4056/document.
Pełny tekst źródłaThe Galactic bulge, as a massive and old Galactic component, is key to understand the physicalprocesses responsibles for the formation of the Galaxy. The spectroscopic study of long lived low massstars represents an opportunity to characterize the detailed chemical and kinematical patterns of theeventual mix of stellar populations building up the bulge. In this thesis we made use of data comingfrom the Gaia-ESO survey to conduct a detailed analysis of the disk system as well as bulge stellarpopulations. The bulge metallicity distribution function is bimodal. The metal-rich population exhibitsbar-like kinematics, displays the double RC feature and overlaps the metal-rich end of the thin disksequence in the [Mg/Fe] vs. [Fe/H] plane. We associate these stars with the bar X-shape bulge formedas the product of secular evolution of the early thin disk. On the other hand, the metal-poor populationpresents isotropic hot kinematics and does not participate in the X-shaped bulge. When compared to thethick disk, bulge stars seem to mimic their distribution in the [Mg/Fe] vs. [Fe/H] plane. Whencomparing the metallicity position of the so called ``knee'', that of the bulge is found to be at [Fe/H]=-0.37+/-0.09 dex, being 0.6 dex higher than that of the thick disk. A chemical evolution model suitablyfits the whole bulge sequence by assuming a fast (<1 Gyr) intense burst of star formation taking place atearly epochs. The origin of the metal-poor bulge still remains unconstrained, but further research shouldallow to distinguish between violent processes or secular evolution for its origin
Granier, Claire. "Les especes metalliques dans la haute atmosphere terrestre (70-110 km) : etude experimentale par sondage laser et modelisation". Paris 6, 1988. http://www.theses.fr/1988PA066269.
Pełny tekst źródłaNeves, Vasco. "Étude sur les paramétres stellaires des naines M et leur lien à la formation planétaire". Thesis, Grenoble, 2013. http://www.theses.fr/2013GRENY082/document.
Pełny tekst źródłaAt the time of writing of this Thesis more than 900 planets have been announced and about 2700 planets from the Kepler space telescope are waiting to be confirmed. The very precise spectra and light curves obtained in Doppler and transit surveys, allows the in-depth study of the parameters of the host stars, and opens the possibility to investigate the star-plant correlations. Also, determining the stellar parameters with precision is critical for more precise determinations of the planetary parameters, namely, mass, radius, and density.In the case of the FGK dwarfs, the determination of stellar parameters is well established and can be used with confidence to study the star-planet relation as well as to obtain precise planetary parameters. However, this is not the case for M dwarfs, the most common stars in the Galaxy. Compared to their hotter cousins, M dwarfs are smaller, colder, and fainter, and therefore harder to study. The biggest challenge regarding M dwarfs is related to the presence of billions of molecular lines that depress the continuum making a classical spectral analysis almost impossible. Finding new and innovative ways to overcome this obstacle in order to obtain precise stellar parameters is the goal of this Thesis.To achieve this goal I focused my research into two main avenues: photometric and spectroscopic methods. My initial work had the objective of establishing a precise photometric metallicity calibration, but I could not reach this goal, as I did not have enough FGK+M binaries with good photometric data. However, it was possible, with the available data, to compare the already established photometric calibrations and slightly improve the best one, as described in Chapter 3.Then, I focused on spectroscopic approaches with the aim of obtaining precise M dwarf parame- ters. To this end I used HARPS high-resolution spectra and developed a method to measure the spectral lines disregarding the continuum completely. Using this method I established a new visible calibration with a precision of 0.08 dex for [Fe/H] and 80 K for Te f f . This work is detailed in Chapter 4.Finally, I also participated in the refinement of the parameters of the star GJ3470 and its planet, where my expertise in stellar parameters of M dwarfs had an important role. The details regarding this investigation are shown in Chapter 5
No momento em que escrevo esta Tese, o número de planetas anunciados já ultrapassou os 900 e os cerca de 2700 candidatos detectados pelo telescópio espacial Kepler esperam por confirmação. Os espectros e as curvas de luz obtidos nos programas de procura de planetas permitem, também, o estudo em profundidade dos parâmetros das estrelas com planetas e abrem a possibilidade de investigar a relação estrela-planeta. Neste contexto, a determinação com precisão dos parâmetros estelares é crítica na determinação precisa dos parâmetros planetários, nomeadamente, a massa, o raio e a densidade.No caso das anãs FGK, os métodos de determinação dos parâmetros estelares estão bem estabelecidos e podem ser usados com confiança no estudo da relação estrela-planeta, assim como na obtenção de parâmetros planetários precisos. No entanto, não é esse o caso para as anãs M, as estrelas mais comuns da nossa Galáxia. Ao contrário das suas primas, as estrelas M são mais pequenas, frias e ténues e, assim sendo, mais difíceis de estudar. O grande entrave no estudo das estrelas M está relacionado com a presença de biliões de linhas moleculares que deprimem o contínuo espectral, fazendo com que uma análise espectral clássica se torne quase impossível. A procura de métodos inovadores que possibilitem ultrapassar este obstáculo, tendo em vista a obtenção de parâmetros precisos, é o objectivo desta Tese.Tendo em conta esse objetivo, foquei os meus esforços em duas linhas principais de pesquisa, baseadas em métodos fotométricos e métodos espectroscópicos. O meu trabalho inicial tinha como objetivo o estabelecimento de uma calibração fotométrica para a metalicidade, mas não me foi possível atingir esse objetivo, pois não tinha sistemas binários FGK+M suficientes com bons dados fotométricos. No entanto, foi possível, com os dados disponíveis, comparar as calibrações fotométricas existentes e refinar ligeiramente a melhor delas, como descrito no Capítulo 3.Após este trabalho passei a concentrar-me em técnicas espectroscópicas de obtenção de parâmetros estelares em estrelas M. Tendo em mente esse objetivo, usei espectros HARPS de alta resolução para desenvolver um novo método de medição de linhas espectrais independente do contínuo espectral. Seguidamente, usei este método no desenvolvimento de uma nova calibração de metalicidade e temperatura efectiva em estrelas M na região do visível, através da qual consegui atingir uma precisão de 0.08 dex para a [Fe/H] e de 80 K para a temperatura. Este trabalho está descrito no Capítulo 4.Ao mesmo tempo colaborei na determinação com precisão dos parâmetros da estrela GJ3470 e do seu planeta, onde a minha proficiência na determinação de parâmetros estelares em anãs M teve um papel importante. Os detalhes relacionados com este trabalho de investigação estão descritos no Capítulo 5
Lagarde, Nadège. "Mélange induit par rotation et instabilité thermohaline dans les étoiles de faible masse et de masse intermédiaire. Conséquences sur l'évolution des éléments légers dans la Galaxie". Phd thesis, 2012. http://tel.archives-ouvertes.fr/tel-00754970.
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