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Digitale Medien

Effects of hyperons on the vibrations of neutron stars (1969)

Langer, William D. ; Cameron, A. G. W.

Springer

Astrophysics and space science 5 (1969), S. 213-253

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ISSN: 1572-946X

Quelle: Springer Online Journal Archives 1860-2000

Thema: Physik

Notizen: Abstract We calculate the effects of hyperons and resonance particles on the vibrations of neutron stars. Vibrating neutron stars can store large amounts of energy in their vibrations; the interaction of the vibrations with the atmosphere would produce electromagnetic radiation. If any process damps out the vibrations rapidly on an astronomical time scale (∼ 1000 years) then vibrating neutron stars are not likely to be found. Previous work indicates that radiation by a neutrino URCA process (N+N→P+N+e −+ $$\bar v_3 $$ ) does not rapidly damp many of the neutron star models. Some neutron stars are predicted to contain massive baryons; here we study thermal damping by nonequilibrium reactions involving these baryons. During vibrations the thermodynamic equilibrium state is changed and particle reactions attempt to restore equilibrium. If the reaction rates per particle are very rapid or slow compared to the frequency of vibration the system follows almost the same pressure-volume curve through both parts of the gas cycle, and very little work is done. In the intermediate case, when reaction rates are comparable to the frequency, damping is rapid. We find that the reaction rates for weak interactions such asN+N↔P+Σ− (the Σ− is the first hyperon to appear with increasing density in degenerate neutron star matter) are of the right magnitude to cause rapid damping. If there is a hyperon region in the star then it cannot sustain vibrations. We also consider the much faster (and hence less important) processN+N↔P+Δ−.

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1007/BF00650292

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2

Digitale Medien

An equation of state at subnuclear densities (1969)

Langer, William D. ; Rosen, Leonard C. ; Cohen, Jeffrey M. ; [weitere]

Springer

Astrophysics and space science 5 (1969), S. 259-271

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ISSN: 1572-946X

Quelle: Springer Online Journal Archives 1860-2000

Thema: Physik

Notizen: Abstract An equation of state for cold matter above white dwarf densities is evaluated. The gas is considered to be a mixture of degenerate neutrons, protons and electrons combined with nuclei of one type (that is only oneA andZ value). We derive the equilibrium equations for the mixture and calculate the number densities as well as theA andZ of the nucleus. Finally we calculate an equation of state, which smoothly goes over to that of a neutron, proton electron gas mixture at a density of ∼5×1013 g/cm3.

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1007/BF00649994

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3

Digitale Medien

Treatment of pulsating white dwarfs including general relativistic effects (1969)

Cohen, Jeffrey M. ; Lapidus, Arnold ; Cameron, A. G. W.

Springer

Astrophysics and space science 5 (1969), S. 113-125

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ISSN: 1572-946X

Quelle: Springer Online Journal Archives 1860-2000

Thema: Physik

Notizen: Abstract In this paper, pulsating white dwarfs are treated via general relativity. Numerical integration of Einstein's equations was used to find equilibrium white dwarfs models and the fundamental periods of small oscillations about these equilibrium models. In these calculations account was taken of coulomb, Thomas-Fermi, and exchange interactions as well as ion zero point energies. It is shown that general relativity makes not just a quantitative difference in the results but a qualitative differences; pure C12 models which are stable in Newtonian mechanics can be unstable against collapse (at a central density of 3×1010 g/cm3) when general relativity is taken into account. The collapsing model may become a neutron star or may continue towards the Schwarzschild radius. More realistic white dwarf models with carbon burning products at the center, also were studied. For these models, the density at which the star becomes unstable against collapse due to electron capture (3×109 g/cm3) was found to be lower than the density at which general relativistic instability occurs.

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1007/BF00653943

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4

Digitale Medien

Untersuchung von Harn, Blut und sonstigem biologischen Material (1938)

Saifer, A. ; Kornblum, M. ; Worden, S. P. ; [weitere]

Springer

Fresenius' Zeitschrift für analytische Chemie 115 (1938), S. 296-300

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ISSN: 1618-2650

Quelle: Springer Online Journal Archives 1860-2000

Thema: Chemie und Pharmazie

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1007/BF01737757

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5

Digitale Medien

Crossing over frequency following inbreeding inNeurospora (1966)

Cameron, H. R. ; Hsu, K. S. ; Perkins, D. D.

Springer

Genetica 37 (1966), S. 1-6

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ISSN: 1573-6857

Quelle: Springer Online Journal Archives 1860-2000

Thema: Biologie

Notizen: Abstract Crossing over frequency was determined for five marked regions covering most of a chromosome arm. The results of a 12th backcross were compared with previously published results from the noninbred f1. Exchange frequency increased significantly following inbreeding. Chiasma interference remained positieve, but was somewhat less intense in b12.

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1007/BF01547114

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6

Digitale Medien

Rapid neutron capture in supernova explosions (1968)

Truran, J. W. ; Arnett, W. D. ; Tsuruta, S. ; [weitere]

Springer

Astrophysics and space science 1 (1968), S. 129-146

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ISSN: 1572-946X

Quelle: Springer Online Journal Archives 1860-2000

Thema: Physik

Notizen: Abstract The implications of recent studies of the dynamics of the cores of highly evolved massive stars are considered with regard to the general problems of nucleosynthesis. The typical conditions estimated for these models are shown to be very promising for the process of element synthesis by neutron capture on a fast time scale (ther-process ofBurbidge et al., 1957).

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1007/BF00653851

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