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  • 1
    Electronic Resource
    Electronic Resource
    [s.l.] : Nature Publishing Group
    Nature 222 (1969), S. 151-153 
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] Direct spectroscopic determination of the abundance of helium in population II stars is quite difficult; and, because of the possibility of gravitational helium depletion caused by inward diffusion in the atmospheres of horizontal branch blue stars4, conclusions from spectroscopic determinations ...
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Amsterdam : Elsevier
    Physics Letters B 324 (1994), S. 425-432 
    ISSN: 0370-2693
    Source: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Topics: Physics
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    Amsterdam : Elsevier
    Physics Letters B 329 (1994), S. 525 
    ISSN: 0370-2693
    Source: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Topics: Physics
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    Amsterdam : Elsevier
    Physics Letters B 303 (1993), S. 68-74 
    ISSN: 0370-2693
    Source: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Topics: Physics
    Type of Medium: Electronic Resource
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  • 5
    Electronic Resource
    Electronic Resource
    Springer
    Astrophysics and space science 28 (1974), S. 303-324 
    ISSN: 1572-946X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract A topological approach in the HR diagram is given for the occurrence and the characteristics of convective envelopes in population II stars. The location of the Hayashi track and of the Red Giants branch are both investigated for various assumed masses of the stars and chemical compositions of the convective layers. An analysis is performed on the influence of the assumed mixing length. The observational consequences of a possible mass loss is discussed for both the Red Giants and the Asymptotic branches. Possible causes for separation between these two branches are briefly examined. The case of the globular cluster ω Cen is investigated, in order to give some suggestions for a large dispersion in colours observed among the giants belonging to this cluster.
    Type of Medium: Electronic Resource
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  • 6
    Electronic Resource
    Electronic Resource
    Springer
    Astrophysics and space science 4 (1969), S. 103-118 
    ISSN: 1572-946X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Description / Table of Contents: Со∂ерисанuе В работе рассчитаны эволюционные пути сдедуюшие за σтадией красных иγантов для моделей звёзд с массами 0,9M ⊙, 0,7M ⊙ и 0,6M ⊙ населения П типа. Исходние модели состгят из гелиевого ядра, содержащего 90% общей массы, и водородной ободочки. Их можно считать ‘остатками’ звезд, потерявших в акте предшествующей эволюции существенную частъ общей массы.
    Abstract: Riassunto È stata calcolata per modelli di stelle di 0,9M ⊙, 0,7M ⊙ e 0,6M ⊙ di Popolazione II l'evoluzione successiva allo stadio di gigante rossa. Inizialmente i modelli constano di un nucleo di elio contenente il 90% della massa totale e di un inviluppo idrogenico. Essi possono interpretarsi come i ‘resti’ di stelle che abbiano perso una frazione di massa considerevole in fasi evolutive precedenti, o all'innesco violento dell'elio al centro.
    Notes: Abstract Evolutionary tracks of 0.9M ⊙, 0.7M ⊙ and 0.6M ⊙ models for Population II stars have been computed in the post-red giant phase. The stars are initially composed of a helium core containing a mass fraction equal to 0.9 and of a hydrogen-rich envelope. They represent hypothetical remnants of stars after substantial mass loss in previous evolutionary phases or/and at the helium flash.
    Type of Medium: Electronic Resource
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  • 7
    Electronic Resource
    Electronic Resource
    Springer
    Astrophysics and space science 73 (1980), S. 11-25 
    ISSN: 1572-946X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract The influence of Main Sequence stellar rotation on horizontal branch stars and on RR Lyrae pulsational properties is studied. Synthetic HB's are computed for a wide range of original chemical compositions taking into account evolutionary effects based on Fusi Pecci-Renzini's evolutionary scheme. Theoretical properties of RR Lyrae pulsators are discussed: it is shown that main sequence rotation is able to induce in HB structures sensitive variations, so that some fundamental relations obtained in the classical frame (i.e., no rotation) have to be released. Consequences on the decodification of observational properties in galactic globular clusters are discussed.
    Type of Medium: Electronic Resource
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  • 8
    Electronic Resource
    Electronic Resource
    Springer
    Astrophysics and space science 10 (1971), S. 355-362 
    ISSN: 1572-946X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Description / Table of Contents: Riassunto Come conseguenza del progressivo aumento in massa per overshooting del nucleo convettivo nella fase iniziale di combustione centrale dell'elio in stelle di ramo orizzontale e per l'andamento del gradiente radiativo della temperatura al bordo del nucleo, viene raggiunto uno stadio nel quale una zona intermedia è instabile rispetto alla convezione. Dalla considerazione dei tempi caratteristici di propagazione della convezione e di combustione nucleare, si conclude che l'instabilità può indurre un mescolamento parziale (semiconvezione) in una regione esterna al nucleo.
    Notes: Abstract In the evolutionary phase of central helium burning, models of horizontal-branch stars reach a stage at which an intermediate region is unstable against convection. This feature is due to the progressive increase of the core mass by overshooting during the previous evolutionary stages and to the behaviour of the radiative temperature gradient at the core boundary. By consideration of the typical time scales of propagation of convection and nuclear burning, a partial mixing (semi-convection) can be induced in a region around the convective core.
    Type of Medium: Electronic Resource
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  • 9
    Electronic Resource
    Electronic Resource
    Springer
    Astrophysics and space science 3 (1969), S. 518-529 
    ISSN: 1572-946X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Description / Table of Contents: Содержание В работе указаны характерныы особенности диаграммы герцпрунга-рессела для шаровых скоплений. При этом уделено особое внимание положксеию и протяжению горизонтальной ветви. Приведено сравнение данных наблюдений со значениами параметров полученных из расчета тволюционных путей с потерей и без потера массы. Приведён также анализ моделей с большим значенмем отношенийq 0 массы гелиевото ядра к обшей массе. Равновесные моделы с двойным лсточнлком энергии расснитанн для значенийq 0 и общей массы псдхдлящих для звёзд горизонтальнои ветви.
    Abstract: Riassunto Sono indicate le principali caratteristiche dei diagrammi H-R degli ammassi globulari con particolare riferimento alla posizione ed alla estensione del ramo orizzontale. Sono esaminate relazioni tra la teoria ed i parametri indicati nei due casi di evoluzione con e senza perdita di massa. E' presentata infine una analisi di modelli con un'alta frazione di massa nel nucleo di elio (q 0). I modelli di equilibrio, non omogenei ed a doppia sorgente di energia, sono stati calcolati in un intervallo di valori diq 0 e della massa totale che sono in relazione alla regione delle stelle del ramo orizzontale.
    Notes: Abstract The most characteristic features of H-R diagrams of blobular clusters are summarized with particular regard to the position and the extension of the horizontal branch. A comparison of observations with theory in the two cases of evolution with and without mass loss is then shortly given. A preliminary approach to the evolution of models with large mass fractions (q 0) in the helium cores is presented. Inhomogeneous equilibrium models with double energy sources have been computed in a range of values ofq 0 and of the total mass referring to possible horizontal-branch stars.
    Type of Medium: Electronic Resource
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  • 10
    Electronic Resource
    Electronic Resource
    Springer
    Astrophysics and space science 46 (1977), S. 195-203 
    ISSN: 1572-946X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract The influence of initial helium content on the evolutionary characteristics of super-metalrich stars (Z=0.10) has been investigated. The evolution of models in the range −0.05〈logL/L ⊙〈1.0 has been followed up to the relative luminosity maximum in the subgiant branch, and under the assumptionY=0.20 orY=0.40. Comparison with previous results suggests the existence of theoretical constraints that could be adopted as metal indicators for the observed H−R diagrams of old open clusters.
    Type of Medium: Electronic Resource
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