Готові списки джерел за темами / Hertzsprung–Russell diagram

Добірка наукової літератури з теми "Hertzsprung–Russell diagram"

Автор: Grafiati
Опубліковано: 14 березня 2023

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Статті в журналах з теми "Hertzsprung–Russell diagram"

1

Langer, N., and R. P. Kudritzki. "The spectroscopic Hertzsprung-Russell diagram." Astronomy & Astrophysics 564 (April 2014): A52. http://dx.doi.org/10.1051/0004-6361/201423374.

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2

MacLeod, Morgan, Matteo Cantiello, and Melinda Soares-Furtado. "Planetary Engulfment in the Hertzsprung–Russell Diagram." Astrophysical Journal 853, no. 1 (January 16, 2018): L1. http://dx.doi.org/10.3847/2041-8213/aaa5fa.

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3

van Loon, Jacco Th. "Cool Stars in the Hertzsprung–Russell Diagram." Proceedings of the International Astronomical Union 11, A29B (August 2015): 475–77. http://dx.doi.org/10.1017/s1743921316005925.

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AbstractAs the opening review to the focus meeting “Stellar Behemoths: Red Supergiants across the Local Universe”, I here provide a brief introduction to red supergiants, setting the stage for subsequent contributions. I highlight some recent activity in the field, and identify areas of progress, areas where progress is needed, and how such progress might be achieved.
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4

Christensen-Dalsgaard, Jørgen. "A Hertzsprung-Russell diagram for stellar oscillations." Symposium - International Astronomical Union 123 (1988): 295–98. http://dx.doi.org/10.1017/s0074180900158279.

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I present evolutionary tracks and curves of constant central hydrogen abundance in diagrams based on frequencies of high-order, low-degree p modes. For stars with masses between 0.7 and 1.5 M⊙, a clean separation is obtained between the effects of varying mass and varying evolutionary state.
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5

Zaninetti, L. "Semi-analytical formulas for the Hertzsprung-Russell diagram." Serbian Astronomical Journal, no. 177 (2008): 73–85. http://dx.doi.org/10.2298/saj0877073z.

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The absolute visual magnitude as function of the observed color (B-V), also named Hertzsprung-Russell diagram, can be described through five equations; that when calibrated stars are available means eight constants. The developed framework allows to deduce the remaining physical parameters, mass, radius and luminosity. This new technique is applied to the first 10 pc, the first 50 pc, the Hyades and to the determination of the distance of a cluster. The case of the white dwarfs is analyzed assuming the absence of calibrated data: our equation produces a smaller ?2 with respect to the standard color-magnitude calibration when applied to the Villanova Catalog of Spectroscopically Identified White Dwarfs. The theoretical basis of the formulas for the colors and the bolometric correction of the stars is clarified by a Taylor expansion in the temperature of the Planck distribution.
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6

Doom, C., J. P. de Greve, and C. de Loore. "Stellar evolution in the upper Hertzsprung-Russell diagram." Astrophysical Journal 303 (April 1986): 136. http://dx.doi.org/10.1086/164060.

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7

Hubrig, S., P. North, and G. Mathys. "Magnetic Ap Stars in the Hertzsprung‐Russell Diagram." Astrophysical Journal 539, no. 1 (August 10, 2000): 352–63. http://dx.doi.org/10.1086/309189.

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8

Jao, Wei-Chun, and Gregory A. Feiden. "An Enhanced Hertzsprung–Russell Diagram Using Gaia EDR3 Data." Research Notes of the AAS 5, no. 5 (May 1, 2021): 124. http://dx.doi.org/10.3847/2515-5172/ac053a.

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9

Farag, Ebraheem, F. X. Timmes, Morgan Taylor, Kelly M. Patton, and R. Farmer. "On Stellar Evolution in a Neutrino Hertzsprung–Russell Diagram." Astrophysical Journal 893, no. 2 (April 23, 2020): 133. http://dx.doi.org/10.3847/1538-4357/ab7f2c.

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10

Arsentieva, A. A., and I. I. Shevchenko. "Host Stars of Planets on the Hertzsprung–Russell Diagram." Astronomy Letters 47, no. 9 (September 2021): 651–60. http://dx.doi.org/10.1134/s1063773721080016.

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Дисертації з теми "Hertzsprung–Russell diagram"

1

Brogt, E. "Pedagogical and curricular thinking of professional astronomers teaching the Hertzsprung-Russell diagram in introductory astronomy courses for non-science majors." Thesis, University of Canterbury. University Centre for Teaching and Learning, 2009. http://gradworks.umi.com/33/52/3352344.html.

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2

Brogt, Erik. "Pedagogical and Curricular Thinking of Professional Astronomers Teaching the Hertzsprung-Russell Diagram in Introductory Astronomy Courses for Non-Science Majors." Diss., The University of Arizona, 2009. http://hdl.handle.net/10150/195246.

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Анотація:
This qualitative study explores the pedagogical and curricular thinking of five professional astronomers, faculty at a university, about teaching the Hertzsprung-Russell diagram in introductory astronomy courses for non-science majors. Data sources for this study included two semi-structured interviews per participant, in which they were asked about teaching the Hertzsprung-Russell diagram, as well as about the introductory course in general. In addition, participants were asked to complete four cognitive tasks; the creation of a lesson plan, a concept map on how they would like their students to think about the Hertzsprung-Russell diagram at the end of the course, a Pathfinder network rating task, and responding to stereotypical student statements regarding the Hertzsprung-Russell diagram.The data was analyzed using a case study approach, followed by a discussion of themes that emerged from the data. Results indicate that participants had primarily affect and process goals for the course, rather than content goals. In addition, they wanted students to view the HR diagram as a part of a flow chart, where input physics (both observed and inferred properties of stars) leads to the construction of the HR diagram, which in turn is used to make inferences about stellar evolution. Participants identified several student difficulties with the HR diagram, among which interpreting a graph was the most pertinent. In several stereotypical student statements, participants responded using the exact same analogies to explain the concepts to the students. This may be indicative of some underlying pedagogical content knowledge.
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3

Fu, Xiaoting. "Evolution of low mass stars: lithium problem and alpha enhanced tracks and isochrones." Doctoral thesis, SISSA, 2016. http://hdl.handle.net/20.500.11767/4919.

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PARSEC (PAdova-TRieste Stellar Evolution Code) is the updated version of the the stellar evolution code used in Padova. It provides stellar tracks and isochrones for stellar mass from 0.1 M ⊙ to 350 M ⊙ and metallicity from Z=0.00001 to 0.06. The evolutionary phases are from pre-main sequence to the thermally pulsing asymptotic giant branch. The core of my Ph.D. project is building a new PARSEC database of α enhanced stellar evolutionary tracks and isochrones for Gaia. Precise studies on the Galactic bulge, globular cluster, Galactic halo and Galactic thick disk require stellar models with α enhancement and various helium contents. It is also important for extra-Galactic studies to have an α enhanced population synthesis. For this purpose we complement existing PARSEC models, which are based on the solar partition of heavy elements, with alpha-enhanced partitions. We collect detailed measurements on the metal mixture and helium abundance for the two populations of 47Tuc (NGC 104) from literature, and calculate stellar tracks and isochrones with these chemical compositions that are alpha-enhanced. By fitting precise color-magnitude diagram with HST ACS/WFC data from low main sequence till horizontal branch, we calibrate some free parameters that are important for the evolution of low mass stars like the mixing at the bottom of the convective envelope. This new calibration significantly improves the prediction of the RGB bump brightness. We also check that the He evolutionary lifetime is correctly predicted by the current version of PARSEC . As a further result of this calibration process, we derive an age of 12.00±0.2 Gyr, distance modulus(m-M) 0 =13.22^{+0.02}_{−0.01} , reddening E(V-I)=0.035^{-0.008} _{+0.005} , and red giant branch mass loss around 0.172 M ⊙ ∼ 0.177 M ⊙ for 47Tuc. We apply the new calibration and alpha-enhanced mixtures of the two 47Tuc populations ( [α/Fe] ∼0.4 and 0.2) to other metallicities. The new models reproduce the RGB bump observations much better than previous models, solving a long-lasting discrepancy concerning its predicted luminosity. This new PARSEC database, with the newly updated alpha-enhanced stellar evolutionary tracks and isochrones, will also be part of the new product for Gaia. Besides the α enhanced metal mixture in 47Tuc, we also calculate evolutionary tracks based on alpha-enhanced metal mixtures derived from ATLAS9 APOGEE atmosphere model. The full set of isochrones with chemical compositions suitable for globular clusters and Galactic bulge stars, will be soon made available online after the full calculation and calibration are performed. PARSEC is able to predict the evolution of stars for any chemical pattern of interest. Lithium is one of the most intriguing and complicated elements. The lithium abundance derived in metal-poor main sequence stars is about three times lower than the value of primordial Li predicted by the standard Big Bang nucleosynthesis when the baryon density is taken from the CMB or the deuterium measurements. This disagreement is generally referred as the “cosmological lithium problem”. We here reconsider the stellar Li evolution from the pre-main sequence to the end of the main sequence phase by introducing the effects of convective overshooting and residual mass accretion. We show that 7 Li could be significantly depleted by convective overshooting in the pre-main sequence phase and then partially restored in the stellar atmosphere by a tail of matter accretion which follows the Li depletion phase and that could be regulated by extreme ultraviolet (EUV) photo-evaporation. By considering the conventional nuclear burning and microscopic diffusion along the main sequence, we can reproduce the Spite plateau for stars with initial mass m 0 = 0.62 − 0.80 M ⊙ , and the Li declining branch for lower mass dwarfs, e.g, m 0 = 0.57 − 0.60 M ⊙ , with a wide range of metallicities (Z=0.00001 to Z=0.0005), starting from an initial Li abundance A(Li) = 2.72. This environmental Li evolution model also offers the possibility to interpret the decrease of Li abundance in extremely metal-poor stars, the Li disparities in spectroscopic binaries and the low Li abundance in planet hosting stars.
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4

Chen, Yang. "Evolution of Very Low Mass Stars and Very Massive Stars in PARSEC." Doctoral thesis, SISSA, 2015. http://hdl.handle.net/20.500.11767/4879.

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During my Ph.D. study, I have been concentrating on the evolutionary tracks and atmosphere models of very low mass stars (VLMSs; ∼ 0.1 − 0.6 Msun) and very massive stars (VMSs; ∼ 12−350 Msun), based on the PAdova-TRieste Stellar Evolution Code (PARSEC). For the very low mass models, it appeared that the previous models computed with PARSEC were unable to correctly predict some basic observational relations. These relations include the mass–radius relation and the colour-magnitude relations of cool dwarfs. We replace the approximate boundary conditions used in PARSEC with those provided by more realistic atmosphere modelling. We implement the T – tau relations from Phoenix/BT-Settl model atmospheres as the outer boundary conditions in the PARSEC code, finding that this change alone reduces the discrepancy in the mass–radius relation from 8 to 5 per cent. Furthermore, we convert the theoretical quantities to the magnitudes and colors with the stellar spectral libraries from Phoenix/BT-Settl. We compare the models with multi–band photometries of clusters Praesepe, M 67, 47 Tuc and NGC 6397, showing that the use of T – tau relations clearly improves the description of the optical colours and magnitudes. However, using both Kurucz and Phoenix model spectra, the models are still systematically fainter and bluer than the observations. We then apply a shift to the above T – tau relations, increasing from 0 at Teff = 4730 K to ∼14 per cent at Teff = 3160 K, to reproduce the observed mass–radius relation of dwarf stars. Taking this experiment as a calibration of the T – tau relations, we can reproduce the optical and near-infrared CMDs of low mass stars in the old metal–poor globular clusters NGC 6397 and 47 Tuc, and in the intermediate–age and young Solar–metallicity open clusters M 67 and Praesepe. Thus, we extend PARSEC models using this calibration, providing VLMS models that are more suitable for the lower main sequence stars over a wide range of metallicities and wavelengths. For the very massive stars, the Padova models were computed more than 20 years ago and were not distributed to the community because suitable bolometric corrections for these models were not yet implemented. In this project, we complement the PARSEC data base with the stellar evolutionary tracks of massive stars, from the pre-main sequence phase to the central Carbon ignition. We consider a broad range of metallicities, 0.0001≤ Z ≤ 0.04 and initial masses up to Mini =350 Msun. The main difference with respect to our previous models of massive stars is the adoption of a recent formalism accounting for the mass-loss enhancement when the ratio of the stellar luminosity to the Eddington luminosity, Γe , approaches unity. With this new formalism, the models are able to reproduce the Humphreys-Davidson limit observed in the Galactic and Large Magellanic Cloud colour-magnitude diagrams, without an ad hoc mass-loss enhancement. We also follow the predictions of recent wind models indicating that the metallicity dependence of the mass-loss rates becomes shallower when Γ e approaches unity. We thus find that massive stars may suffer from substantial mass-loss even at low metallicity. We also predict that the Humphreys-Davidson limit should become brighter at decreasing metallicity. We supplement the evolutionary tracks with new theoretical bolometric correction tables, useful for comparing tracks and isochrones with the observations. For this purpose, we homogenize existing stellar atmosphere libraries of hot and cool stars (PoWR, ATLAS9 and Phoenix) and add, where needed, new atmosphere models computed with WM-basic. The model grids are fully adequate in mass, age and metallicity for performing detailed investigations of the properties of very young stellar systems in both local and distant galaxies. The new tracks supersede the previous old Padova models of massive stars. Therefore, my work together with the already updated PARSEC models of the other masses could depict the full evolution of stars across the mass range from ∼ 0.08 Msun to 350 Msun and over a wide range of metallicity from super-Solar (Z = 0.04) to extreme metal-poor (Z = 0.0001). Consequently, they would provide paramount information for studies not only on stars or star clusters but also on galaxy formation and evolution.
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5

Weisz, Daniel R., Sergey E. Koposov, Andrew E. Dolphin, Vasily Belokurov, Mark Gieles, Mario L. Mateo, Edward W. Olszewski, Alison Sills, and Matthew G. Walker. "A HUBBLE SPACE TELESCOPE STUDY OF THE ENIGMATIC MILKY WAY HALO GLOBULAR CLUSTER CRATER." IOP PUBLISHING LTD, 2016. http://hdl.handle.net/10150/621220.

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We analyze the resolved stellar populations of the faint stellar system, Crater, based on deep optical imaging taken with the Advanced Camera for Surveys on the Hubble Space Telescope. Crater's color-magnitude diagram (CMD) extends similar to 4 mag below the oldest main-sequence (MS) turnoff. Structurally, we find that Crater has a half-light radius of similar to 20 pc and no evidence for tidal distortions. We model. Crater's CMD as a simple stellar population (SSP) and alternatively by solving for its full star formation history. In both cases, Crater is well. described by an SSP with an age of similar to 7.5 Gyr, a metallicity of [ M / H] similar to 1.65, a total stellar mass of M-star similar to 1e4 M-circle dot, and. a luminosity of M-V similar to - 5.3, located at a distance of d similar to 145 kpc, with modest uncertainties due to differences in the underlying stellar evolution models. We argue that the sparse sampling of stars above the turnoff and subgiant branch are likely to be 1.0-1.4 M-circle dot blue stragglers and their evolved descendants, as opposed to intermediate- age MS stars. We find that. Crater is an unusually young cluster given its location in the Galaxy's outer halo. We discuss scenarios for Crater's origin, including the possibility of being stripped from the SMC or the accretion from lower- mass dwarfs such as Leo I or Carina. Despite uncertainty over its progenitor system, Crater appears to have been incorporated into the Galaxy more recently than z similar to 1 (8 Gyr ago), providing an important new constraint on the accretion history of the Galaxy.
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6

Girardi, Mauricio. "Construção do diagrama Hertzsprung-Russel através do stellarium : uma proposta para explorar conceitos de física moderna e contemporânea no ensino médio." reponame:Biblioteca Digital de Teses e Dissertações da UFRGS, 2017. http://hdl.handle.net/10183/175181.

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Анотація:
Neste trabalho propõe-se explorar conceitos de Física Moderna e Contemporânea (FMC) a partir de fenômenos físicos presentes na física estelar, utilizando o software Stellarium como ferramenta no desenvolvimento de atividades voltadas à construção coletiva de um diagrama Hertzsprung-Russell (diagrama H-R), que é um diagrama muito importante da astrofísica para classificação das estrelas. À luz da teoria de Lev S. Vygotsky, é proposto que os alunos trabalhem em grupos, de forma colaborativa, tanto na obtenção de parâmetros astrofísicos estelares a partir do software, quanto na construção do diagrama H-R. O uso do software, ao mesmo tempo em que serve de ferramenta no processo de mediação segundo a teoria Vygotskyana, também cumpre o papel de inserir o uso da tecnologia em sala de aula como recurso didático. Espectro eletromagnético, radiação de corpo negro, quantização da energia, luminosidade, cor e temperatura em função do comprimento de onda das radiações, são alguns dos conceitos de FMC abordados. Conceitos estes que constam nos programas nas disciplinas de Física das escolas, mas nem sempre são abordados ou em muitas ocasiões abordados de forma isolada ou descontextualizada. O trabalho foi desenvolvido em uma turma de 31 alunos do Segundo Ano do Ensino Médio no Colégio Estadual Piratini, em Porto Alegre – RS durante seis encontros (três de 100 minutos e três de 150 minutos), entre outubro e dezembro de 2016. Como produto deste trabalho é apresentado uma seqüência didática ao professor de Física com a perspectiva de sugerir possibilidades de abordagens dos conceitos de FMC através da astronomia e da astrofísica em um processo coletivo, mediado pelo uso de softwares, em especial, o Stellarium.
In this study is proposed to explore the concepts of Modern and Contemporary Physics through physical phenomena present on stellar physics, using the Stellarium software as a tool on the development of activities related to the collective construction of a Hertzsprung-Russell diagram (H-R diagram), which is a very important diagram in Astrophysics for the classification of stars. Based on Lev S. Vygotsky’s theory, it is proposed that the students work collaboratively in groups, both in obtaining astrophysical parameters of the stars using the software, as in the construction of a H-R diagram. According to the Vygotsky’s theory, the software can help on the process of mediation, while it also fultfils the role of bringing technology into classroom as a learning resource. Electromagnetic spectrum, blackbody radiation, energy quantization, luminosity, color and temperature, according to radiation wavelength are some of the Modern and Contemporary Physics concepts approached. These concepts are included on the program of Physics at schools, but they sometimes are not taught, or in many occasions are studied in an isolated, decontextualized manner. The project was conducted on a High School second grade class with 31 students at Colégio Estadual Piratini, in Porto Alegre – RS, during six classes (three of 100 minutes and three of 150 minutes), between October and December, 2016. As a result of this study, a didactical sequence is presented to the Physics teacher intending to suggest possible ways of approaching the Modern and Contemporary Physics concepts through Astronomy and Astrophysics, in a collective process, intermediated by the use of softwares, specially the Stellarium software.
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7

Bell, Cameron Pearce MacDonald. "A critical assessment of ages derived using pre-main-sequence isochrones in colour-magnitude diagrams." Thesis, University of Exeter, 2012. http://hdl.handle.net/10036/4017.

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In this thesis a critical assessment of the ages derived using theoretical pre-main-sequence (pre-MS) stellar evolutionary models is presented by comparing the predictions to the low-mass pre-MS population of 14 young star-forming regions (SFRs) in colour-magnitude diagrams (CMDs). Deriving pre-MS ages requires precise distances and estimates of the reddening. Therefore, the main-sequence (MS) members of the SFRs have been used to derive a self-consistent set of statistically robust ages, distances and reddenings with associated uncertainties using a maximum-likelihood fitting statistic and MS evolutionary models. A photometric method (known as the Q-method) for de-reddening individual stars in regions where the extinction is spatially variable has been updated and is presented. The effects of both the model dependency and the SFR composition on these derived parameters are also discussed. The problem of calibrating photometric observations of red pre-MS stars is examined and it is shown that using observations of MS stars to transform the data into a standard photometric system can introduce significant errors in the position of the pre-MS locus in CMD space. Hence, it is crucial that precise photometric studies (especially of pre- MS objects) be carried out in the natural photometric system of the observations. This therefore requires a robust model of the system responses for the instrument used, and thus the calculated responses for the Wide-Field Camera on the Isaac Newton Telescope are presented. These system responses have been tested using standard star observations and have been shown to be a good representation of the photometric system. A benchmark test for the pre-MS evolutionary models is performed by comparing them to a set of well-calibrated CMDs of the Pleiades in the wavelength regime 0.4−2.5 μm. The masses predicted by these models are also tested against dynamical masses using a sample of MS binaries by calculating the system magnitude in a given photometric band- pass. This analysis shows that for Teff ≤ 4000 K the models systematically overestimate the flux by a factor of 2 at 0.5 μm, though this decreases with wavelength, becoming negligible at 2.2 μm. Thus before the pre-MS models are used to derive ages, a recalibration of the models is performed by incorporating an empirical colour-Teff relation and bolometric corrections based on the Ks-band luminosity of Pleiades members, with theoretical corrections for the dependence on the surface gravity (log g). The recalibrated pre-MS model isochrones are used to derive ages from the pre-MS populations of the SFRs. These ages are then compared with the MS derivations, thus providing a powerful diagnostic tool with which to discriminate between the different pre- MS age scales that arise from a much stronger model dependency in the pre-MS regime. The revised ages assigned to each of the 14 SFRs are up to a factor two older than previous derivations, a result with wide-ranging implications, including that circumstellar discs survive longer and that the average Class II lifetime is greater than currently believed.
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8

Milone, A. P., A. F. Marino, L. R. Bedin, J. Anderson, D. Apai, A. Bellini, P. Bergeron, A. J. Burgasser, A. Dotter, and J. M. Rees. "The HST large programme on omega Centauri - I. Multiple stellar populations at the bottom of the main sequence probed in NIR-Optical." OXFORD UNIV PRESS, 2017. http://hdl.handle.net/10150/624420.

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As part of a large investigation with Hubble Space Telescope to study the faintest stars within the globular cluster omega Centauri, in this work we present early results on the multiplicity of its main sequence (MS) stars, based on deep optical and near-infrared observations. By using appropriate colour-magnitude diagrams, we have identified, for the first time, the two main stellar Populations I and II along the entire MS, from the turn-off towards the hydrogen-burning limit. We have compared the observations with suitable synthetic spectra of MS stars and conclude that the two main sequences (MSs) are consistent with stellar populations with different metallicity, helium and light-element abundance. Specifically, MS-I corresponds to a metal-poor stellar population ([Fe/H] similar to -1.7) with Y similar to 0.25 and [O/Fe] similar to 0.30. The MS-II hosts helium-rich (Y similar to 0.37-0.40) stars with metallicity ranging from [Fe/H] similar to -1.7 to -1.4. Below the MS knee (m(F160W) similar to 19.5), our photometry reveals that each of the two main MSs hosts stellar subpopulations with different oxygen abundances, with very O-poor stars ([O/Fe] similar to -0.5) populating the MS-II. Such a complexity has never been observed in previous studies of M-dwarfs in globular clusters. A few months before the launch of the James Webb Space Telescope, these results demonstrate the power of optical and near-infrared photometry in the study of multiple stellar populations in globular clusters.
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9

Mattioli, Giulia. "Reazioni termonucleari nei nuclei stellari." Bachelor's thesis, Alma Mater Studiorum - Università di Bologna, 2021. http://amslaurea.unibo.it/24275/.

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Анотація:
In questo lavoro di tesi si descrivono le principali reazioni termonucleari che sono il principale meccanismo di produzione energetica nei nuclei stellari. La trattazione è stata effettuata seguendo un approccio interdisciplinare, evidenziando il collegamento tra aspetti di meccanica quantistica, fisica nucleare e astrofisica. L'obiettivo della tesi è fornire un quadro completo e organico dell'argomento e legare le catene di bruciamenti termonucleari alle diverse fasi dell'evoluzione stellare. Nel primo capitolo si è effettuata una trattazione fisica e matematica per poter definire il tasso di reazione termonucleare e il tasso di produzione energetica, quantità fondamentali per lo studio dei fenomeni di produzione energetica all'interno delle stelle. Nel secondo capitolo si è voluto entrare nel dettaglio del meccanismo delle reazioni termonucleari, analizzando le principali catene coinvolte nel bruciamento dell'idrogeno e dell'elio (PP chain, ciclo CNO, reazione 3-alfa) e fornendone anche un bilancio energetico. Nel terzo capitolo si sono inserite le nozioni precedentemente date nel contesto astrofisico: come tali reazioni nucleari possano influenzare il percorso evolutivo di una stella, in base alla sua massa e composizione chimica.
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10

Dieterich, Sergio Bonucci. "Characterization of the Stellar / Substellar Boundary." 2013. http://scholarworks.gsu.edu/phy_astr_diss/66.

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The aim of this dissertation is to address the topic of distinguishing very low mass stars from brown dwarfs through observational means. To that end, we seek to better characterize both populations and establish mechanisms that facilitate establishing an individual object's membership in either the very low mass star or the brown dwarf populations. The dissertation is composed of three separate observational studies. In the first study we report on our analysis of HST/NICMOS snapshot high resolution images of 255 stars in 201 systems within ~10 parsecs of the Sun. We establish magnitude and separation limits for which companions can be ruled out for each star in the sample, and then perform a comprehensive sensitivity and completeness analysis for the subsample of 138 M dwarfs in 126 systems. We calculate a multiplicity fraction of $0.0-0.0+3.5% for L companions to M dwarfs in the separation range of 5 to 70 AU, and $2.3-0.7+5.0% for L and T companions to M dwarfs in the separation range of 10 to 70 AU. Considering these results and results from several other studies, we argue that the so-called "brown dwarf desert" extends to binary systems with low mass primaries and is largely independent of primary mass, mass ratio, and separation. In the second study we construct a Hertzsprung-Russell diagram for the stellar/substellar boundary based on a sample of 63 objects ranging in spectral type from M6V to L4. We report new VRI photometry for 63 objects and new trigonometric parallaxes for 37 objects. We employ a novel SED fitting algorithm to determine effective temperatures, bolometric luminosities, and radii. We find evidence for the local minimum in the radius-temperature and radius-luminosity trends that may indicate the end of the stellar main sequence and the start of the brown dwarf sequence at $Teff ~2075K, log(L/Lsun) ~ -3.9, and (R/Rsun) ~ 0.086. The third study is a pilot study for future work and part of a long term search for astrometric binaries that have the potential to yield dynamical masses. We report the discovery of five new multiple systems and discuss their potential for determining dynamical masses: LHS 2071AB, GJ 1215 ABC, LTT 7434 AB, LHS 501 AC, and LHS 3738 AB.
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Книги з теми "Hertzsprung–Russell diagram"

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Gautier, Mathys, Solanki Sami K, and Wickramasinghe D. T, eds. Magnetic fields across the Hertzsprung-Russell diagram: Proceedings of a workshop held in Santiago, Chile, 15-19 January 2001. San Francisco, Calif: Astronomical Society of the Pacific, 2001.

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(Editor), Gautier Mathys, S. K. Solanki (Editor), and D. T. Wickramasinghe (Editor), eds. Magnetic Fields Across the Hertzsprung-Russell Diagram: Proceedings of a Workshop Held in Santiago Chile, 15-19 January 2001 (Astronomical Society of the Pacific conference series). Astronomical Society of the Pacific, 2001.

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Частини книг з теми "Hertzsprung–Russell diagram"

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Montmerle, Thierry, and Sylvia Ekström. "Hertzsprung-Russell Diagram." In Encyclopedia of Astrobiology, 1–7. Berlin, Heidelberg: Springer Berlin Heidelberg, 2014. http://dx.doi.org/10.1007/978-3-642-27833-4_717-7.

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Brill, Michael H. "Hertzsprung-Russell Diagram." In Encyclopedia of Color Science and Technology, 1–2. Berlin, Heidelberg: Springer Berlin Heidelberg, 2015. http://dx.doi.org/10.1007/978-3-642-27851-8_188-2.

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Brill, Michael H. "Hertzsprung-Russell Diagram." In Encyclopedia of Color Science and Technology, 1–2. Berlin, Heidelberg: Springer Berlin Heidelberg, 2019. http://dx.doi.org/10.1007/978-3-642-27851-8_188-3.

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Montmerle, Thierry, and Sylvia Ekström. "Hertzsprung-Russell Diagram." In Encyclopedia of Astrobiology, 1099–105. Berlin, Heidelberg: Springer Berlin Heidelberg, 2015. http://dx.doi.org/10.1007/978-3-662-44185-5_717.

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Montmerle, Thierry, and Sylvia Ekström. "Hertzsprung–Russell Diagram." In Encyclopedia of Astrobiology, 749–54. Berlin, Heidelberg: Springer Berlin Heidelberg, 2011. http://dx.doi.org/10.1007/978-3-642-11274-4_717.

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Brill, Michael H. "Hertzsprung-Russell Diagram." In Encyclopedia of Color Science and Technology, 717–18. New York, NY: Springer New York, 2016. http://dx.doi.org/10.1007/978-1-4419-8071-7_188.

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Inglis, Michael. "The Hertzsprung-Russell Diagram." In The Patrick Moore Practical Astronomy Series, 77–84. Cham: Springer International Publishing, 2014. http://dx.doi.org/10.1007/978-3-319-11644-0_4.

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Inglis, Michael. "The Hertzsprung-Russell Diagram." In The Patrick Moore Practical Astronomy Series, 99–107. Cham: Springer International Publishing, 2023. http://dx.doi.org/10.1007/978-3-031-16805-5_4.

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Zwaan, Cornelis. "Magnetic Activity Across the Hertzsprung-Russell Diagram." In Mechanisms of Chromospheric and Coronal Heating, 241–56. Berlin, Heidelberg: Springer Berlin Heidelberg, 1991. http://dx.doi.org/10.1007/978-3-642-87455-0_45.

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Dalsgaard, Jørgen Christensen. "A Hertzsprung-Russell Diagram For Stellar Oscillations." In Advances in Helio- and Asteroseismology, 295–98. Dordrecht: Springer Netherlands, 1988. http://dx.doi.org/10.1007/978-94-009-4009-3_65.

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Тези доповідей конференцій з теми "Hertzsprung–Russell diagram"

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Aimran Wan Mohd Kamil, Wan Mohd, Nurul Shazana Abdul Hamid, Marlia Puteh, Nurhasmiza Abu Hasan Sazalli, Lilie Zahara Ramly, Ayu Rita Mohamad, Othman Zainon, et al. "Using Interactive Applet to Support Collaborative Learning of The Hertzsprung-Russell Diagram." In 2019 6th International Conference on Space Science and Communication (IconSpace). IEEE, 2019. http://dx.doi.org/10.1109/iconspace.2019.8905949.

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