Star interiors

Physics of Neutron Star Interiors , D. Blaschke, N.K. Glendenning, and A. Sedrakian (eds.), Springer, in press. 

Color superconductivity (CS) in quark matter [1] is one interesting aspect of the physics of compact star interiors [2], Since calculations of the energy... 

In order to answer the question whether strange quark matter phases should be expected in the neutron star interiors, we consider here a three-flavor generalization of a NCQM with the action... 

Blaschke D.,Grigorian H.,Poghosyan G., 2001, Physics of Neutron Star Interiors, Lecture Notes in Physics 578, p.285, Springer-Verlag. 

Keywords Stars interiors - Stars evolution - Stars horizontal-branch -Stars AGB and post-AGB - HR and C-M diagrams - Equation of state -Convection - Atomic Processes - Nucleosynthesis... 

Keywords nuclear reactions, nucleosynthesis, abundances stars interiors supernovae general neutrinos circumstellar matter X-rays stars... 

An increase in concentration Oion of added salt ions, leads to the penetration of salt ions into the star interior and a decrease in the differential osmotic pressure. When the concentration of added ions sufficiently exceeds the average concentration of counterions in the osmotic star, the polyion is found in the so-called salt-dominated regime. Here, the differential osmotic pressure of ions is equivalent to that created by binary monomer-monomer interactions with an effective second viral coefficient Ueff = a /24>ion. As a result, one recovers the same scaling dependence for the size of a PE star as that found for neutral star polymer under good solvent conditions, (4), with replacement u —> Uetr ... 

It can be shown that the addition of trace amounts of Z-ions to the solution leads to a rapid substitution of monovalent counterion in the star corona by Z-ions. This is due to their stronger attraction to the oppositely charged PE star polymer. Since a smaller number of Z-ions is needed to ensure the electroneutrality of the star interior, an increase in (i.e., in relative amount of Z-ions in the bulk of the solution) leads to a rapid decrease in the osmotic pressure inside the corona and, consequently, to a de-swelling of the PE star. This effect, of replacing monovalent counterions by multivalent ones is most pronounced at low salt concentrations (in the osmotic regime), where ... 

In addition to these laboratory-based experiments it is interesting to note that the Swan bands of C2 are important in astrophysics. They have been observed in the emission spectra of comets and also in the absorption spectra of stellar atmospheres, including that of the sun, in which the interior of the star acts as the continuum source. 

Hydrodynamic marked the beginning of fluid dynamics—the study of the way fluids and gases behave. Each particle in a gas obeys Isaac Newton s laws of motion, but instead of simple planetary motion, a much richer variety of behavior can be observed. In the third century B.C.E., Archimedes of Syracuse studied fluids at rest, hydrostatics, but it was nearly 2,000 years before Daniel Bernoulli took the next step. Using calculus, he combined Archimedes idea of pressure with Newton s laws of motion. Fluid dynamics is a vast area of study that can be used to describe many phenomena, from the study of simple fluids such as water, to the behavior of the plasma in the interior of stars, and even interstellar gases. 

The composition of the Earth was determined both by the chemical composition of the solar nebula, from which the sun and planets formed, and by the nature of the physical processes that concentrated materials to form planets. The bulk elemental and isotopic composition of the nebula is believed, or usually assumed to be identical to that of the sun. The few exceptions to this include elements and isotopes such as lithium and deuterium that are destroyed in the bulk of the sun s interior by nuclear reactions. The composition of the sun as determined by optical spectroscopy is similar to the majority of stars in our galaxy, and accordingly the relative abundances of the elements in the sun are referred to as "cosmic abundances." Although the cosmic abundance pattern is commonly seen in other stars there are dramatic exceptions, such as stars composed of iron or solid nuclear matter, as in the case with neutron stars. The... 

During the red giant phase of stellar evolution, free neutrons are generated by reactions such as C(a,n) and Ne(a,n) Mg. (The (ot,n) notation signifies a nuclear reaction where an alpha particle combines with the first nucleus and a neutron is ejected to form the second nucleus.) The neutrons, having no charge, can interact with nuclei of any mass at the existing temperatures and can in principle build up the elements to Bi, the heaviest stable element. The steady source of neutrons in the interiors of stable, evolved stars produces what is known as the "s process," the buildup of heavy elements by the slow interaction with a low flux of neutrons. The more rapid "r process" occurs in... 

Although the half-life of "Tc in steller interiors is remarkably decreased, a substantial amount of the isotope ean survive the s-process. Observations have revealed that more than 50 stars contain technetium in their outer envelope. According to other calculations, the production of neutrons in the competitive processes of neutron capture and / -decay is even more enhanced at such high temperatures, and this fact almost compensates for the depletion of "Tc [41]. 

The formation of stars in the interiors of dense interstellar clouds affects the chemistry of the immediate environment in a variety of ways depending on many factors such as the stage in the evolution of star formation, the mass of the star or protostar, and the density and temperature of the surrounding material. In general, the dynamics of the material in the vicinity of a newly forming star are complex and show many manifestations. Table 3 contains a list of some of the better studied such manifestations, which tend to have distinctive chemistries. These are discussed individually below. 

Abstract. In this contribution we present the results based on high-resolution spectra of 45 clump stars of the Galactic field. The main atmospheric parameters and abundances of 12C, 13C, N, O and other mixing sensitive chemical elements were investigated. Elemental ratios in the sample of field stars are compared to the results available for evolved stars in open clusters and to the theoretical prediction of extra mixing in stellar interiors. 

The age at which Li depletion occurs increases with decreasing mass (and Li-burning temperatures are never reached for M < 0.06 M0). As luminosity, L oc M2 for PMS stars, the luminosity at which complete Li depletion takes place is therefore a sensitive function of age between about 10 and 200 Myr [6]. This relationship depends little on ingredients of the PMS models such as the treatments of convection and interior radiative opacities because the stars are... 

Opacity effects are also important. This can refer to differences in the treatment of interior opacities or to the effects of uncertain stellar compositions on the opacities. An increase in opacity makes temperature gradients larger, keeps the star convective for longer, raises Tf,cz once the radiative core develops and so leads to enhanced Li depletion. Opacity is increased by an increase in overall metallicity or a decrease in the Helium abundance. Changes of only 0.1 dex in metallicity can lead to an order of magnitude change in Li depletion (e.g. see Fig. 2 of [37]). 

Composition Variations Li depletion is sensitive to interior opacities, which themselves depend on the stellar composition. Small star-to-star variations might cause an Li abundance scatter, which would grow towards lower masses. However, current limits on metallicity variations in the Pleiades (and other clusters) seem too small for this to be the dominant explanation of any scatter [38]. In addition, the correlation of Li-depletion with rotation is unexplained. 

Abstract. The observations of light elements (Lithium and Beryllium) in Globular Cluster (GC) stars are reviewed. Light element observations in GC are very powerful tracers of mixing processes in the stellar interior and shed new light on the GC formation history. 

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