نتایج جستجو برای: stars evolution
تعداد نتایج: 389513 فیلتر نتایج به سال:
In this review we concentrate on the dynamical evolution of the Milky Way as monitored in the solar neighbourhood. The relevant data sets are presented and discussed in detail. In the second part we review various mechanisms, which drive the dynamical evolution. 1. Dynamical evolution of the galactic disk traced in the solar neighbourhood The key data set, which we use for this study, is the Fo...
We investigate the evolution of metal deficient stars, presentingH-burning isochrones covering cluster ages from800 Myr to 7 Gyr. Evolutionary evidences for selection effects in the metallicity distribution of very metal poor H-burning red giants are reported. The evolution of stars during central and shell He burning is further investigated, discussing the occurrence of He burning pulsators as...
In this review, we describe the physical processes driving the dynamical evolution of binary stars, namely the circularization of the orbit and the synchronization of their spin and orbital rotation. We also discuss the possible role of the elliptic instability which turns out to be an unavoidable ingredient of the evolution of binary stars.
We construct a simple dynamical model of the massive globular cluster ω Cen. The model includes simple treatments of dynamical evolution in a galactic tide, and evolution of single stars. Binary stars and rotation are neglected. The model approximately fits observational data on the surface brightness profile, the profile of radial velocity dispersion, and the main sequence mass function at two...
The main astrophysical factories of fluorine (F) are thought to be Type II supernovae, Wolf–Rayet stars, and the asymptotic giant branch (AGB) of intermediate mass stars. We present a model for the chemical evolution of fluorine in the Milky Way using a semi-analytic multi-zone chemical evolution model. For the first time, we demonstrate quantitatively the impact of fluorine nucleosynthesis in ...
The characteristics of black-hole X-ray binaries can be used to obtain information about their evolutionary history and the process of black-hole formation. In this paper I focus on systems with donor masses lower than the inferred black-hole masses. Current models for the evolution of hydrogen-rich, massive stars and of helium stars losing mass in a wind cannot explain the current sample of bl...
We introduce a set of stellar models for massive stars whose evolution has been affected by mass transfer in a binary system, at a range of metallicities. As noted by other authors, the effect of such mass transfer is frequently more than just rejuvenation. We find that, whilst stars with convective cores which have accreted only H-rich matter rejuvenate as expected, those stars which have accr...
The presence of a nearby companion alters the evolution of massive stars in binary systems, leading to phenomena such as stellar mergers, x-ray binaries, and gamma-ray bursts. Unambiguous constraints on the fraction of massive stars affected by binary interaction were lacking. We simultaneously measured all relevant binary characteristics in a sample of Galactic massive O stars and quantified t...
The chemical properties of dwarf spheroidals in the local group are shown to be inconsistent with star formation being truncated after the reionization epoch (z∼ 8). Enhanced levels of [Ba/Y] in stars in dwarf spheroidals like Sculptor indicate strong s-process production from low-mass stars whose lifetimes are comparable with the duration of the pre-reionization epoch. The chemical evolution o...
We have derived elemental abundances of O, Ni as well as for a number of s-elements for 47 G and K dwarf, with Me/H]> 0:1 dex. The selection of stars was based on their kinematics as well as on their uvby ?-photometry. One sample of stars on rather eccentric orbits traces the chemical evolution interior to the solar orbit and another, on circular orbits, the evolution around the solar orbit. A ...
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