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Добірка наукової літератури з теми "Stellar chemical abundances"

Автор: Grafiati

Опубліковано: 10 березня 2023

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Статті в журналах з теми "Stellar chemical abundances"

Tanaka, S., S. Kitamoto, T. Suzuki, K. Torii, M. F. Corcoran, and W. Waldron. "Chemical Abundances of Early Type Stars." Symposium - International Astronomical Union 188 (1998): 224–25. http://dx.doi.org/10.1017/s007418090011486x.

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X-rays from early-type stars are emitted by the corona or the stellar wind. The materials in the surface layer of early-type stars are not contaminated by nuclear reactions in the stellar inside. Therefore, abundance study of the early-type stars provides us an information of the abundances of the original gas. However, the X-ray observations indicate low-metallicity, which is about 0.3 times of cosmic abundances. This fact raises the problem on the cosmic abundances.

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de Mijolla, Damien, and Melissa K. Ness. "Measuring Chemical Likeness of Stars with Relevant Scaled Component Analysis." Astrophysical Journal 926, no. 2 (February 1, 2022): 193. http://dx.doi.org/10.3847/1538-4357/ac46a0.

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Abstract Identification of chemically similar stars using elemental abundances is core to many pursuits within Galactic archeology. However, measuring the chemical likeness of stars using abundances directly is limited by systematic imprints of imperfect synthetic spectra in abundance derivation. We present a novel data-driven model that is capable of identifying chemically similar stars from spectra alone. We call this relevant scaled component analysis (RSCA). RSCA finds a mapping from stellar spectra to a representation that optimizes recovery of known open clusters. By design, RSCA amplifies factors of chemical abundance variation and minimizes those of nonchemical parameters, such as instrument systematics. The resultant representation of stellar spectra can therefore be used for precise measurements of chemical similarity between stars. We validate RSCA using 185 cluster stars in 22 open clusters in the Apache Point Observatory Galactic Evolution Experiment survey. We quantify our performance in measuring chemical similarity using a reference set of 151,145 field stars. We find that our representation identifies known stellar siblings more effectively than stellar-abundance measurements. Using RSCA, 1.8% of pairs of field stars are as similar as birth siblings, compared to 2.3% when using stellar-abundance labels. We find that almost all of the information within spectra leveraged by RSCA fits into a two-dimensional basis, which we link to [Fe/H] and α-element abundances. We conclude that chemical tagging of stars to their birth clusters remains prohibitive. However, using the spectra has noticeable gain, and our approach is poised to benefit from larger data sets and improved algorithm designs.

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Van der Swaelmen, M., V. Hill, F. Primas, and A. A. Cole. "Chemical abundances in LMC stellar populations." Astronomy & Astrophysics 560 (December 2013): A44. http://dx.doi.org/10.1051/0004-6361/201321109.

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Pompéia, L., V. Hill, M. Spite, A. Cole, F. Primas, M. Romaniello, L. Pasquini, M. R. Cioni, and T. Smecker Hane. "Chemical abundances in LMC stellar populations." Astronomy & Astrophysics 480, no. 2 (January 9, 2008): 379–95. http://dx.doi.org/10.1051/0004-6361:20064854.

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Leckrone, David S., Sveneric Johansson, Glenn M. Wahlgren, Charles R. Proffitt, and Tomas Brage. "Stellar chemical abundances with the GHRS." Physica Scripta T65 (January 1, 1996): 110–14. http://dx.doi.org/10.1088/0031-8949/1996/t65/015.

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Moya, A., L. M. Sarro, E. Delgado-Mena, W. J. Chaplin, V. Adibekyan, and S. Blanco-Cuaresma. "Stellar dating using chemical clocks and Bayesian inference." Astronomy & Astrophysics 660 (April 2022): A15. http://dx.doi.org/10.1051/0004-6361/202141125.

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Context. Dating stars is a major challenge with a deep impact on many astrophysical fields. One of the most promising techniques for this is using chemical abundances. Recent space- and ground-based facilities have improved the quantity of stars with accurate observations. This has opened the door for using Bayesian inference tools to maximise the information we can extract from them. Aims. Our aim is to present accurate and reliable stellar age estimates of FGK stars using chemical abundances and stellar parameters. Methods. We used one of the most flexible Bayesian inference techniques (hierarchical Bayesian models) to exceed current possibilities in the use of chemical abundances for stellar dating. Our model is a data-driven model. We used a training set that has been presented in the literature with ages estimated with isochrones and accurate stellar abundances and general characteristics. The core of the model is a prescription of certain abundance ratios as linear combinations of stellar properties including age. We gathered four different testing sets to assess the accuracy, precision, and limits of our model. We also trained a model using chemical abundances alone. Results. We found that our age estimates and those coming from asteroseismology, other accurate sources, and also with ten Gaia benchmark stars agree well. The mean absolute difference of our estimates compared with those used as reference is 0.9 Ga, with a mean difference of 0.01 Ga. When using open clusters, we reached a very good agreement for Hyades, NGC 2632, Ruprecht 147, and IC 4651. We also found outliers that are a reflection of chemical peculiarities and/or stars at the limit of the validity ranges of the training set. The model that only uses chemical abundances shows slightly worse mean absolute difference (1.18 Ga) and mean difference (−0.12 Ga).

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Sbordone, L., L. Monaco, S. Duffau, P. Bonifacio, and E. Caffau. "A wide angle chemical survey of the Sagittarius dwarf Spheroidal galaxy." Proceedings of the International Astronomical Union 14, S344 (August 2018): 42–45. http://dx.doi.org/10.1017/s1743921318006804.

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AbstractWe present the status of an ongoing project to map the detailed chemical abundances of stars across the main body of the Sagittarius dwarf Spheroidal galaxy (Sgr dSph). The Sgr dSph is the closest known dwarf galaxy, and is being tidally destroyed by its interaction with the Milky Way (MW), leaving behind a massive stellar stream. Sgr dSph is a chemically outstanding object, with peculiar abundance ratios, clear center-outskirts abundance gradients, and spanning more than 3 orders of magnitude in metallicity. We present here detailed abundances from UVES@VLT spectra for more than 50 giants across 8 fields along the major and minor axes of Sgr dSph, and 5 more outside the galaxy main body, but possibly associated to its stellar stream.

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Tolstoy, Eline, and Kim Venn. "Stellar Abundances in Local Group Galaxies." Highlights of Astronomy 13 (2005): 548–53. http://dx.doi.org/10.1017/s1539299600016567.

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AbstractHere we describe some of our latest results from measuring detailed abundances in Local Group dwarf galaxies with the VLT. Combining spectroscopic abundances with Color-Magnitude diagrams allows the effective measurement of detailed chemical evolution with time in these galaxies. Although there are not yet significant numbers of individual stars observed in local group dwarf galaxies, the uniformity of the abundance patterns of the majority of stars in galaxies with very different star formation histories must hint at general properties of all star formation in these small systems.

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Matteucci, Francesca. "Chemical enrichment and feedback in low metallicity environments: constraints on galaxy formation." Proceedings of the International Astronomical Union 4, S255 (June 2008): 134–41. http://dx.doi.org/10.1017/s1743921308024708.

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AbstractChemical evolution models for dwarf metal poor galaxies, including dwarf irregulars and dwarf spheroidals will be presented. The main ingredients necessary to build detailed models of chemical evolution including stellar nucleosynthesis, supernova progenitors, stellar lifetimes and stellar feedback will be discussed. The stellar feedback will be analysed in connection with the development of galactic winds in dwarf galaxies and their effects on the predicted abundances and abundance ratios. Model results concerning α-elements (O, Mg, Si, Ca), Fe and s-and r-process elements will be discussed and compared with the most recent observational data for metal poor galaxies of the Local Group. We will show how the study of abundance ratios versus abundances can represent a very powerful tool to infer constraints on galaxy formation mechanisms. In this framework, we will discuss whether, on the basis of their chemical properties, the dwarf galaxies of the Local Group could have been the building blocks of the Milky Way.

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Patrick, Lee R., Chris J. Evans, Ben Davies, Rolf-Peter Kudritzki, Maria Bergemann, and Annette N. M. Ferguson. "Red Supergiants as Chemical Abundance Probes: The Local Group dwarf NGC6822." Proceedings of the International Astronomical Union 14, S344 (August 2018): 213–16. http://dx.doi.org/10.1017/s174392131800649x.

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AbstractRed Supergiant Stars (RSGs) are important probes of stellar and chemical evolution in star-forming environments. They represent the brightest near-IR stellar components of external galaxies and probe the most recent stellar population to provide robust, independent abundance estimates. The Local Group dwarf irregular galaxy, NGC6822, is a reasonably isolated galaxy with an interesting structure and turbulent history. Using RSGs as chemical abundance probes, we estimate metallicities in the central region of NGC6822, finding a suggestion of a metallicity gradient (in broad agreement with nebular tracers), however, this requires further study for confirmation. With intermediate resolution Multi-object spectroscopy (from e.g. KMOS, EMIR, MOSFIRE) combined with state-of-the-art stellar model atmospheres, we demonstrate how RSGs can be used to estimate stellar abundances in external galaxies. In this context, we compare stellar and nebular abundance tracers in NGC 6822 and by combining stellar and nebular tracers we estimate an abundance gradient of −0.18 ± 0.05 dex/kpc.

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Дисертації з теми "Stellar chemical abundances"

García, Pérez Ana E., Carlos Allende Prieto, Jon A. Holtzman, Matthew Shetrone, Szabolcs Mészáros, Dmitry Bizyaev, Ricardo Carrera, et al. "ASPCAP: THE APOGEE STELLAR PARAMETER AND CHEMICAL ABUNDANCES PIPELINE." IOP PUBLISHING LTD, 2016. http://hdl.handle.net/10150/621372.

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The Apache Point Observatory Galactic Evolution Experiment (APOGEE) has built the largest moderately high-resolution (R approximate to 22,500) spectroscopic map of the stars across the Milky Way, and including dust-obscured areas. The APOGEE Stellar Parameter and Chemical Abundances Pipeline (ASPCAP) is the software developed for the automated analysis of these spectra. ASPCAP determines atmospheric parameters and chemical abundances from observed spectra by comparing observed spectra to libraries of theoretical spectra, using. 2 minimization in a multidimensional parameter space. The package consists of a FORTRAN90 code that does the actual minimization and a wrapper IDL code for book-keeping and data handling. This paper explains in detail the ASPCAP components and functionality, and presents results from a number of tests designed to check its performance. ASPCAP provides stellar effective temperatures, surface gravities, and metallicities precise to 2%, 0.1 dex, and 0.05 dex, respectively, for most APOGEE stars, which are predominantly giants. It also provides abundances for up to 15 chemical elements with various levels of precision, typically under 0.1 dex. The final data release (DR12) of the Sloan Digital Sky Survey III contains an APOGEE database of more than 150,000 stars. ASPCAP development continues in the SDSS-IV APOGEE-2 survey.

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Marino, Anna. "Multiple stellar populations in Globular Clusters: spectroscopic evidence." Doctoral thesis, Università degli studi di Padova, 2010. http://hdl.handle.net/11577/3427339.

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Globular cluster (GC) stars have occupied a fundamental role in our understanding of stellar evolution thanks to the assumption that their stars can be idealized as a simple stellar population, i.e. coeval and chemically homogeneous. However, there is a growing body of observational facts which challenge this traditional view, revealing the presence of multiple stellar populations in GCs. In this thesis I present my contribution to the study of multiple populations in GCs mainly from the spectroscopic point of view. By taking advantage of high and mid-resolution spectra collected at various telescopes, I studied the chemical abundances for large sample of stars in the GCs, M4, M22, and Omega Centauri. All the three studied cases show evidence of multiple populations, but they reveal themselves in different ways, indicating that these GCs have experienced different enrichment histories. Thanks to the analysis of chemical content of stars belonging to distinct stellar populations, important informations have been obtained on the nature of the progenitors that enriched the intracluster medium from which the second generation formed.
Il ruolo fondamentale che gli ammassi globulari (AG) hanno storicamente occupato negli studi di evoluzione stellare si deve all'assunzione per cui tutte le stelle di un ammasso costituiscano una popolazione stellare semplice, cioe' siano coeve e chimicamente omogenee. Tuttavia, una crescente quantita' di dati osservativi sta mettendo in crisi questa visione tradizionale, rivelando la presenza di popolazioni stellari multiple all'interno di uno stesso AG. In questa tesi discutero' il mio contributo, principalmente spettroscopico, allo studio delle popolazioni multiple in AG. Dall'analisi di spettri ad alta e media risoluzione ottenuti in diversi telescopi, ho determinato le abbondanze chimiche per vasti campioni di stelle negli AG M4, M22 e Omega Centauri. Tutti e tre i casi di AG studiati mostrano evidenze di popolazioni multiple, che si manifestano pero' in maniera differente, indicando che questi oggetti hanno subito una diversa evoluzione di arricchimento chimico. Grazie all'analisi del contenuto chimico di stelle appartenenti a popolazioni distinte, sono state ottenute importanti informazioni sulla natura dei progenitori che hanno arricchito il mezzo dal quale si e' formata la seconda generazione di stelle.

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Collet, Remo. "On the Chemical Composition of Metal-Poor Stars : Impact of Stellar Granulation and Departures from Local Thermodynamic Equilibrium on the Formation of Spectral Lines." Doctoral thesis, Uppsala University, Department of Astronomy and Space Physics, 2006. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-7121.

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The information about the chemical compositions of stars is encoded in their spectra. Accurate determinations of these compositions are crucial for our understanding of stellar nucleosynthesis and Galactic chemical evolution. The determination of elemental abundances in stars requires models for the stellar atmospheres and the processes of line formation. Nearly all spectroscopic analyses of late-type stars carried out today are based on one-dimensional (1D), hydrostatic model atmospheres and on the assumption of local thermodynamic equilibrium (LTE). This approach can lead to large systematic errors in the predicted stellar atmospheric structures and line-strengths, and, hence, in the derived stellar abundances. In this thesis, examples of departures from LTE and from hydrostatic equilibrium are explored. The effects of background line opacities (line-blocking) due to atomic lines on the statistical equilibrium of Fe are investigated in late-type stars. Accounting for this line opacity is important at solar metallicity, where line-blocking significantly reduces the rates of radiatively induced ionizations of Fe. On the contrary, the effects of line-blocking in metal-poor stars are insignificant. In metal-poor stars, the dominant uncertainty in the statistical equilibrium of Fe is the treatment of inelastic H+Fe collisions. Substantial departures of Fe abundances from LTE are found at low metallicities: about 0.3 dex with efficient H+Fe collisions and about 0.5 dex without. The impact of three-dimensional (3D) hydrodynamical model atmospheres on line formation in red giant stars is also investigated. Inhomogeneities and correlated velocity fields in 3D models and differences between the mean 3D stratifications and corresponding 1D model atmospheres can significantly affect the predicted line strengths and derived abundances, in particular at very low metallicities. In LTE, the differences between 3D and 1D abundances of C, N, and O derived from CH, NH, and OH weak low-excitation lines are in the range -0.5 dex to -1.0 dex at [Fe/H]=-3. Large negative corrections (about -0.8 dex) are also found in LTE for weak low-excitation neutral Fe lines. We also investigate the impact of 3D hydrodynamical model stellar atmospheres on the determination of elemental abundances in the carbon-rich, hyper iron-poor stars HE 0107-5240 and HE 1327-2326. The lower temperatures of the line-forming regions of the 3D models compared with 1D models cause changes in the predicted spectral line strengths. In particular we find the 3D abundances of C, N, and O to be lower by about -0.8 dex (or more) than estimated from a 1D analysis. The 3D abundance of Fe is decreased but only by -0.2 dex. Departures from LTE for Fe might actually be very large for these stars and dominate over the effects due to granulation.

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Jonsell, Karin. "Chemical Abundance Analysis of Population II Stars : The Summary Includes a Background in General Astronomy." Doctoral thesis, Uppsala University, Department of Astronomy and Space Physics, 2005. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-6034.

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We are made of stardust in the sense that most atomic nuclei around us have been formed by stars. Stars synthesise new elements and expel them to the interstellar medium, from which later new generations of stars are born. We can map this chemical evolution by analysing the atmospheric contents of old Galactic halo stars. I have done two such investigations. A vigourous debate is going on whether the oxygen-to-iron ratio varies strongly with the general metal-content of halo stars. In my first study, I made an abundance analysis of 43 halo stars, and found no support for such a variation. I have also found that there probably is a cosmic spread in the abundances of oxygen, magnesium, silicon, and calcium relative to iron for halo stars. This may be an indication that the halo was built up by subsystems with differences in the star formation rate. In my second study, I performed a thorough abundance analysis of the star HE0338-3945, which is strangely overabundant in both r- and s-elements. Several other stars have been found with abundance patterns curiously similar to this star, and I define new criteria for the class r+s stars. The abundance similarities among the r+s stars suggest a common formation scenario. However, as the s-elements usually are considered to be produced in binary systems of low mass, and r-elements in supernovae of Type II, this scenario is not obvious. In the article I discuss seven hypotheses, and several of them are dismissed.

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Thorén, Patrik. "Dwarf and Subgiant Stars as Probes of Galactic Chemical and Dynamical Evolution." Doctoral thesis, Uppsala universitet, Uppsala Astronomiska Observatorium, 2001. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-636.

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Stellar chemical abundances provide astronomers with vital information about the production of chemical elements. Some stars preserve the composition of the environment in which they were born on their surfaces. By analysing the light from a star, the abundances of elements, its age and its path in space can be derived, and translated into the language of galactic history. The spallative history of boron in the early Galaxy was reinvestigated by observations of an ultraviolet spectral line in the old star HD 140283 with the Hubble Space Telescope. The line was barely detected and the upper limit abundance derived was lower than expected, which calls for further observations of this line in halo stars. Stars evolved into subgiants were observed with the ESO CAT, La Silla, and NOT, La Palma, to deduce their usefulness for galactic evolution studies. The high resolution spectroscopy study of the 26 objects showed that these stars are indeed useful for such studies. They are more luminous than dwarf stars and their ages can be accurately derived. They do not seem to have changed their surface abundances due to their evolution into giants. Subgiants can successfully be used to observationally reach regions further from the Earth, which can remove local biases that may appear when only observing nearby dwarf stars. A NLTE investigation of neutral Ca showed that cool metal rich dwarf stars did not deviate significantly from LTE, as had earlier been suggested. By an LTE analysis of a sample of 17 such dwarfs, using recent MARCS atmospheres, synthetic spectroscopy and modern atomic line data, cool metal rich dwarfs were shown not to deviate significantly from the expected abundance patterns in a number of elements. This increases the number of potential targets for studies of galactic chemical evolution in the metal rich regime since most stars are cool.

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Stonkutė, Edita. "Chemical composition of kinematically identified galactic stellar group." Doctoral thesis, Lithuanian Academic Libraries Network (LABT), 2013. http://vddb.laba.lt/obj/LT-eLABa-0001:E.02~2013~D_20130925_093107-33619.

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A number of stellar streams, moving and kinematic groups were identified in the Milky Way galaxy. Some of them are suspected to originate from accreted satellites. Can we also find such traces of ancient merger events in the solar neighbourhood? Helmi et al. (2006) identified three new coherent groups of stars in the Geneva-Copenhagen survey (Nordström et al. 2004) and suggested that those might correspond to remains of disrupted satellites. With the detailed chemical composition analysis of the newly identified kinematic group we aim to contribute to the Galactic substructure studies. The main aim of the study is to perform a high-resolution spectroscopic elemental abundance analysis in stars belonging to one of the newly identified kinematic groups and to compare the results with other stars in the Galactic disc. We performed the detailed chemical analysis of 21 stars attributed to Group 3 of the Geneva-Copenhagen survey and six comparison Galactic thin disc stars. The main atmospheric parameters and abundances of 22 chemical elements were determined. All programme stars are overabundant in oxygen and α-elements compared with the Galactic thin-disc. This abundance pattern has similar characteristics to those of the Galactic thick disc. The abundances of chemical elements produced predominantly by the r-process are overabundant in comparison with Galactic thin-disc dwarfs of the same metallicity. The abundances of iron-group elements and chemical elements produced mainly... [to full text]
Paukščių Tako galaktikoje yra identifikuota žvaigždžių srautų, judančių bei kinematinių grupių, kurių kilmė siejama su įkritusiomis galaktikomis. Aktualu ištirti, ar yra tokių senųjų substruktūrų pėdsakų mūsų Saulės aplinkoje? Helmi ir kt. (2006), panaudoję Nordström ir kt. (2004) Ženevos–Kopenhagos apžvalgos (ŽKA) katalogą, identifikavo tris naujas koherentines žvaigždžių grupes, kurios pasižymi išskirtiniais kinematiniais parametrais ir gali būti užgalaktinės kilmės. Šiuo disertacijos darbu siekiama prisidėti prie Galaktikos substruktūrų tyrimų, nustatant detalią cheminę vienos iš Helmi ir kt. identifikuotų žvaigždžių grupių sudėtį. Svarbu išsiaiškinant, ar ŽKA kinematinės grupės žvaigždžių atmosferų cheminė sudėtis skiriasi nuo Galaktikos disko žvaigždžių. Nustatėme 21 3–osios ŽKA kinematinės grupės bei 6 palyginamųjų plonojo disko žvaigždžių atmosferų pagrindinius parametrus bei 22 cheminių elementų gausas. Kinematinės žvaigždžių grupės deguonies ir α–elementų gausos yra padidėjusios lyginant su plonuoju disku ir yra panašios į storojo disko. Cheminių elementų, daugiausia pagaminamų s–procese, gausos ir geležies grupės elementų gausos yra panašios į to paties metalingumo plonojo disko nykštukių cheminių elementų gausas, o cheminių elementų, daugiausia pagaminamų r–procese, gausos yra padidėjusios lyginant su plonuoju disku. Panaši cheminė tirtos kinematinės grupės bei storojo Galaktikos disko sudėtis rodo, kad kinematinės žvaigždžių grupės ir storojo disko žvaigždžių... [toliau žr. visą tekstą]

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Laws, Christopher S. "The chemically peculiar nature of stars with planets : searching for signatures of accretion in stellar photospheres /." Thesis, Connect to this title online; UW restricted, 2004. http://hdl.handle.net/1773/5430.

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Thévenin, Frédéric. "Contribution a l'etude des abondances des populations stellaires." Paris 7, 1987. http://www.theses.fr/1987PA077294.

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Presentation des resultats et difficultes rencontres en abordant les problemes d'evolution des galaxies et plus precisement de la galaxie. Un exemple d'application sur les etoiles naines f montre qu'elles ne subissent aucune anomalie d'abondances en elements lourds par la physique particuliere de leurs atmospheres. La spectrometrie a basse resolution ( equiv. A 2a) est abordee. Une application a la structure galactique et a la photometrie rgu de bale est presentee. Le spectrometre multifentes essefem qui repond au besoin de spectrographie statistique est presente et discut

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Vick, Mathieu. "Étude de l'influence de la perte de masse sur l'évolution d'étoiles de plusieurs types." Thèse, Montpellier 2, 2010. http://hdl.handle.net/1866/4609.

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Byström, Amanda. "Archaeologic inspection of the Milky Way using vibrations of a fossil : Seismic, spectroscopic and kinematic characterization of a binary metal-poor Halo star." Thesis, Uppsala universitet, Observationell astrofysik, 2020. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-416391.

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Анотація:

The Milky Way has undergone several mergers with other galaxies during its lifetime. The mergers have been identified via stellar debris in the Halo of the Milky Way. The practice of mapping these mergers is called galactic archaeology. To perform this archaeologic inspection, three stellar features must be mapped: chemistry, kinematics and age. Historically, the latter has been difficult to determine, but can today to high degree be determined through asteroseismology. Red giants are well fit for these analyses. In this thesis, the red giant HE1405-0822 is completely characterized, using spectroscopy, asteroseismology and orbit integration, to map its origin. HE1405-0822 is a CEMP-r/s enhanced star in a binary system. Spectroscopy and asteroseismology are used in concert, iteratively to get precise stellar parameters, abundances and age. Its kinematics are analyzed, e.g. in action and velocity space, to see if it belongs to any known kinematical substructures in the Halo. It is shown that the mass accretion that HE1405-0822 has undergone has given it a seemingly younger age than probable. The binary probably transfered C- and s-process rich matter, but how it gained its r-process enhancement is still unknown. It also does not seem like the star comes from a known merger event based on its kinematics, and could possibly be a heated thick disk star.
Vintergatan har genomgått flera sammanslagningar med andra galaxer under sin livstid. Dessa sammanslagningar har identifierats genom rester av stjärnor i Vintergatans Halo. Arbetssättet för att kartlägga dessa sammanslagningar kallas galaktisk arkeologi. För att kunna göra en arkeologisk undersökning krävs tre egenskaper hos de undersökta stjärnorna: kemi, kinematik och ålder. Historiskt sett har den sistnämnda varit svår att bestämma, men kan idag bestämmas med hög precision m.h.a. asteroseismologi. Röda jättar lämpar sig väl för dessa analyser. I denna uppsats undersöks den röda jätten HE1405-0822. Den kartläggs helt m.h.a. spektroskopi, asteroseismologi och bananalys. HE1405-0822 är en CEMP-r/s-förhöjd stjärna i ett binärt system. Spektroskopi och asteroseismologi används tillsammans, iterativt, för att få precisa stjärnparametrar, kemiskt innehåll och ålder. Dess kinematik analyseras, t.ex. i verkan- och hastighetsrummet, för att se om den tillhör någon känd kinematisk substruktur i Halon. Det visas att massöverföringen som HE1405-0822 genomgått har gett den en skenbart yngre ålder än vad som är troligt. Denna binära kompanjon har troligtvis övertfört C- och s-process-rikt material, men hur den fick sin mängd r-processämnen är fortfarande okänt. Det verkar inte som att stjärnan kommer från någon tidigare kartlagd sammanslagning baserat på dess kinematik, och skulle kunna vara en stjärna med upphettad kinematik från Vintergatans tjocka disk.

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Книги з теми "Stellar chemical abundances"

Lee, Duane Morris. Understanding the Nature of Stellar Chemical Abundance Distributions in Nearby Stellar Systems. [New York, N.Y.?]: [publisher not identified], 2014.

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United States. National Aeronautics and Space Administration., ed. Model stellar atmospheres and real stellar atmospheres and status of the ATLAS12 opacity sampling program and of new programs for Rosseland and for distribution function opacity. [Washington, DC: National Aeronautics and Space Administration, 1996.

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Kurucz, Robert L. Model stellar atmospheres and real stellar atmospheres and status of the ATLAS12 opacity sampling program and of new programs for Rosseland and for distribution function opacity. [Washington, DC: National Aeronautics and Space Administration, 1996.

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Wehrse, Rainer. Accuracy of Element Abundances from Stellar Atmospheres: Proceedings of Two Sessions Allocated at the IAU General Assembly in Baltimore, USA, August ... in Physics). Springer, 2014.

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Частини книг з теми "Stellar chemical abundances"

Worthey, Guy. "Chemical Abundances in Old Populations." In The Stellar Populations of Galaxies, 507. Dordrecht: Springer Netherlands, 1992. http://dx.doi.org/10.1007/978-94-011-2434-8_174.

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Nissen, Poul Erik. "Chemical Abundances as Population Tracers." In Planets, Stars and Stellar Systems, 21–54. Dordrecht: Springer Netherlands, 2013. http://dx.doi.org/10.1007/978-94-007-5612-0_2.

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Acker, A., J. Köppen, B. Stenholm, and G. Jasniewicz. "Chemical Abundances of Galactic Planetary Nebulae." In The Stellar Populations of Galaxies, 383. Dordrecht: Springer Netherlands, 1992. http://dx.doi.org/10.1007/978-94-011-2434-8_50.

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Giovagnoli, A., and M. Tosi. "Chemical Evolution Models with a New Stellar Nucleosynthesis." In The Light Element Abundances, 137–40. Berlin, Heidelberg: Springer Berlin Heidelberg, 1995. http://dx.doi.org/10.1007/978-3-540-49169-9_20.

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Ryan, Sean G. "Element Abundances and Galactic Chemical Evolution." In The Influence of Binaries on Stellar Population Studies, 491–506. Dordrecht: Springer Netherlands, 2001. http://dx.doi.org/10.1007/978-94-015-9723-4_35.

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Alvensleben, Uta Fritze-V., and Klaus J. Fricke. "Metal Abundances of Damped Lyα Systems and the Chemical Evolution of Spiral Galaxies." In Stellar Populations, 457. Dordrecht: Springer Netherlands, 1995. http://dx.doi.org/10.1007/978-94-011-0125-7_124.

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Alvensleben, Uta Fritze-V., and Klaus J. Fricke. "Metal Abundances of Damped Lyα Systems and the Chemical Evolution of Spiral Galaxies." In Stellar Populations, 424. Dordrecht: Springer Netherlands, 1995. http://dx.doi.org/10.1007/978-94-011-0125-7_96.

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Primas, F. "Light Elements Abundances: New Insights on Stellar Mixing and Galactic Production." In Cosmic Chemical Evolution, 17–21. Dordrecht: Springer Netherlands, 2002. http://dx.doi.org/10.1007/978-94-010-0452-7_2.

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Przybilla, Norbert, Keith Butler, Sylvia Becker, Rolf-Peter Kudritzki, Kim A. Venn, James K. McCarthy, and Andreas Kaufer. "Extragalactic Stellar Abundances: Oxygen in Extreme A-Type Supergiants." In Chemical Evolution from Zero to High Redshift, 123. Berlin, Heidelberg: Springer Berlin Heidelberg, 1999. http://dx.doi.org/10.1007/978-3-540-48360-1_29.

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Dolginov, A. Z. "Chemical and Temperature Inhomogeneities on Stellar Surfaces as a Result of an Instability." In Upper Main Sequence Stars with Anomalous Abundances, 395–96. Dordrecht: Springer Netherlands, 1986. http://dx.doi.org/10.1007/978-94-009-4714-6_62.

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Тези доповідей конференцій з теми "Stellar chemical abundances"

Ishigaki, Miho N., Wako Aoki, and Masashi Chiba. "Chemical abundances of the Milky Way thick disk and stellar halo." In FIRST STARS IV – FROM HAYASHI TO THE FUTURE –. AIP, 2012. http://dx.doi.org/10.1063/1.4754393.

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Dobrovolskas, Vidas, Arunas Kucinskas, Hans G. Ludwig, Elisabetta Caffau, Jonas Klevas, and Dainius Prakapavicius. "Chemical abundances in metal-poor giants: limitations imposed by the use of classical 1D stellar atmosphere models." In 11th Symposium on Nuclei in the Cosmos. Trieste, Italy: Sissa Medialab, 2011. http://dx.doi.org/10.22323/1.100.0288.

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