Dense stars and problems of their detection.
Extraterrestrial detection and final evolution of presupernova stars culminating in neutron star formation
SUPERNOVA↗
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Results for “STAR EVOLUTION”
Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.
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A theory of the origin and evolution of contact binaries
Theory of origin and evolution of contact binary stars
BINARY STAR↗
Dynamics and evolution of close binary systems
Dynamics and evolution of eclipsing binary star
DYNAMICS↗
Stellar evolution. VII.
Evolution of 2.25 M star from main sequence to helium burning phase noting lifetimes, nuclear burning of core, stellar mass fraction and stellar model algorithm
GIANT STAR↗
Abundance anomalies produced by nuclear reactions in stellar surface layers. I.
Energetic nuclear bombardment effects on stellar surface element abundance calculated with statistical theory in A magnetic variable star abundance anomaly
VARIABLE STAR↗
Massive stars
Normal O, blue supergiants and brightest yellow and red supergiant massive stars, considering evolution, luminosity, lifetime mass loss, pulsational instability and supernovae
Stothers, R.↗
Emission nebulae in the Magellanic Clouds. I - The H II regions
A review of optical and radio studies of the H II regions in the Magellanic Clouds is presented. Recent studies are emphasized, particularly optical studies of the kinematics, spectra, and chemical composition. The implications of the studies for the understanding of the evolution of stars and galaxies in general, and the Magellanic Clouds in particular, are noted. Suggestions for future work are also given.
Dufour, R. J.↗
Isotopic anomalies in the galactic cosmic-ray source
Observations of the isotopic compositions of oxygen, neon and magnesium nuclei in galactic cosmic rays are presented and discussed in terms of nucleosynthesis at the galactic cosmic ray source. The observations, made with a charged-particle telescope carried aboard ISEE-3, show enhancements in the Ne-22/Ne-20, Mg-25/Mg-24 and Mg-26/Mg-24 ratios with respect to solar system abundances by factors of 4.1, 1.6 and 1.6, respectively. The data thus demonstrate that the galactic cosmic ray source is compositionally distinct from the solar system, and also rule out the models of Woolsey and Weaver (in press) for the synthesis of excess Ne-22 and a model of normal star formation, evolution and mass loss in a region enriched in metals.
Wiedenbeck, M. E.↗
Understand B-type stars
When observations of B stars made from space are added to observations made from the ground and the total body of observational information is confronted with theoretical expectations about B stars, it is clear that nonthermal phenomena occur in the atmospheres of B stars. The nature of these phenomena and what they imply about the physical state of a B star and how a B star evolves are examined using knowledge of the spectrum of a B star as a key to obtaining an understanding of what a B star is like. Three approaches to modeling stellar structure (atmospheres) are considered, the characteristic properties of a mantle, and B stars and evolution are discussed.
Source record↗
X-ray imaging - Supernova remnants
Consideration is given to imaging observations of supernova remnants (SNRs) obtained during the first year of the Einstein Observatory's operation. Inferences are drawn regarding models for stellar explosions, remnant evolution, neutron star formation and the interstellar medium. Because the X-ray emission traces the expanding shock boundary and dominates the radiative energy losses of an SNR over much of its lifetime, it can provide data on the possible collapsed remnants of the explosion, such as neutron stars and/or black holes. X-ray emission also allows a supernova shock to be used as a probe of interstellar medium structure. The imaging instrument aboard the Einstein satellite has been used to observe over 30 known Galactic remnants, and a similar number of objects in other galaxies, in the 0.15-4.5 keV band.
Helfand, D. J.↗
Windows on the axion
Peccei-Quinn symmetry with attendant axion is a most compelling, and perhaps the most minimal, extension of the standard model, as it provides a very elegant solution to the nagging strong CP-problem associated with the theta vacuum structure of QCD. However, particle physics gives little guidance as to the axion mass; a priori, the plausible values span the range: 10(-12)eV is approx. less than m(a) which is approx. less than 10(6)eV, some 18 orders-of-magnitude. Laboratory experiments have excluded masses greater than 10(4)eV, leaving unprobed some 16 orders-of-magnitude. Axions have a host of interesting astrophysical and cosmological effects, including, modifying the evolution of stars of all types (our sun, red giants, white dwarfs, and neutron stars), contributing significantly to the mass density of the Universe today, and producting detectable line radiation through the decays of relic axions. Consideration of these effects has probed 14 orders-of-magnitude in axion mass, and has left open only two windows for further exploration: 10(-6)eV is approx. less than m(a) is approx. less than 10(-3)eV and 1eV is approx. less than m(a) is approx. less than 5eV (hadronic axions only). Both these windows are accessible to experiment, and a variety of very interesting experiments, all of which involve heavenly axions, are being planned or are underway.
Turner, Michael S.↗
Red-giant evolution, metallicity, and new bounds on hadronic axions
Stellar cooling by nuclear axion emission is explored, identifying those special isotopes that dominate this process for temperatures from 10 to the 7th to 10 to the 9th K. It is argued that such nuclear energy-loss mechanisms are distinctive because the effects track metallicity. Three observables associated with evolution of stars along the red-giant and horizontal branches are shown to impose new and restrictive constraints on axions in the hadronic window.
Haxton, W. C.↗
Ultraviolet imaging of globular clusters and galaxies
The techniques of UV imaging and its scientific potential are reviewed for studies of advanced stellar evolution, the star formation history and interstellar medium of galaxies, active nuclei, and the evolutionary state of systems observed at high redshift. Early Hubble Space Telescope imaging is expected to emphasize such programs since its image quality is excellent by earlier standards for the UV, despite the presence of spherical aberration.
O'Connell, Robert W.↗
On the evolution of slowly accreting neutron stars
In the light of recent calculations of pycnonuclear reaction rates for light elements, we consider the problem of slow interstellar accretion onto old, possibly magnetized neutron stars. We argue that accretion will occur at the Hoyle-Lyttleton rate after the star has spun down in less than about 10 exp 9 yr. A deep ocean of liquid hydrogen and helium, extending down to depths about 100 m, will cover the surface of the star once it has accreted about 10 exp 25 g of gas. Beneath the ocean will be a layer of almost pure solid O-16 which undergoes two-stage electron capture to C-16 above a pressure 2.7 x 10 exp 28 dyne/sq cm, corresponding to an accreted mass of about 10 exp 27 g. Taking into account the presence of multiple layers of distinct chemical composition, we conclude that the crust will be stable to small perturbations under the conditions envisaged for instellar accretion. A thick layer of up to 10 exp 27 g of metastable C-16 will then accumulate. We discuss the implications of these results to old Galactic neutron stars as sources of gamma-ray bursts.
Blaes, O. M.↗
Hydrodynamical evolution of coalescing binary neutron stars
The hydrodynamics of the final merging of two neutron stars and the corresponding gravitational wave emission is studied in detail. Various test calculations are presented, including the compressible Roche and Darwin problems and the head-on collision of two polytropes. A complete coalescence calculation is presented for the simplest case of two identical neutron stars, represented by Gamma = 2 polytropes, in a circular orbit, with their spins aligned and synchronized with the orbital rotation.
Rasio, Frederic A.↗
Astrophysics from the moon
Ideas presented at the Workshop on Astrophysics from the moon, held in Annapolis, Maryland, in February 1990, are discussed. Consideration is given to the formation of stars and planetary systems, the possibility of earthlike planets among the nearby stars, the possible existence of life and intelligence elsewhere, the current status of the sun and other stars, the evolution of the early universe, and environmental and site considerations for initial observatories.
Mumma, Michael J.↗
On partial mixing zones in horizontal-branch stellar cores
The present semianalytical treatment for aspects of horizontal branch (HB) star core evolution considers a criterion for the existence of a partial mixing zone in a general stellar model. This criterion implies that there must be a zone with a composition gradient. Attention is given to the consequences of the assumption for the behavior of the core close to the central He exhaustion; with the degree of mixing implied by the constraint on the temperature gradient, core opacity tends to a limit late in evolution, and then declines. The central opacity and flux decreases give the convective region a strong tendency to shrink.
Dorman, Ben↗
Variety in planetary systems
Observation of circumstellar disks, regular satellite systems of outer planets, and planet-size objects orbiting pulsars support the supposition that formation of planetary systems is a robust, rather than a fragile, byproduct of the formation and evolution of stars. The extent to which these systems may be expected to resemble one another and our Solar System, either in overall structure or in detail remains uncertain. When the full range of possible stellar masses, disk masses, and initial specific angular momenta are considered, the possible variety of planetary configurations is very large. Numerical modeling indicates a difference between the formation of small, inner, terrestrial planets and the outer planets.
Wetherill, George W.↗