bluuebunny/crossref_metadata_2025_split huggingface dataset:
Dynamics of the Antonov-Nuritdinov Planar Galaxy Model
Authors: Sridhar S. 
Published: July 2016

AbstractA time dependent solution of the collisionless Boltzmann equation (CBE) in two space dimensions first given by Antonov and Nuritdinov is discussed further. The solution is self consistent with a quadratic potential and represents a generalised Freeman bar characterised by 10 parameters. Because of two conserved quantities, they form an 8-dimensional phase space. Geometric and group theoretical aspects of this dynamical system are discussed. Systems of this type can show chaotic oscillations in general. This study raises interesting general questions about time dependent solutions of the CBE.
Long-Term Predictions for Highly Eccentric Orbits
Authors: Ferrándiz José M. , Sansaturio M. Eugenia , Vigo Jesús 
Published: July 2016

AbstractPredictability in orbital behaviour of artificial satellites depends on several factors: the accuracy required, the particular dynamical models formulated, the sets of variables chosen to describe them, the numerical or analytical techniques used and, specially, the specific trajectories to be established. In this paper we address the problem of predictability for highly eccentric satellites with (J2 + J22)-perturbation, by using numerical techniques to integrate the equations of motion when expressed in different sets of regular variables.
Fragility in Cosmology and Astrophysics
Authors: Tavakol R.K. 
Published: July 2016

AbstractThe theoretical framework adopted in astrophysics and cosmology, in both modelling and the analysis of the observational data, is often implicitly assumed to be that of structural stability. Here, in view of some of the recent results in dynamical systems theory, it is argued that such a framework cannot be assumed a priori and that the fragility framework may instead turn out to be the appropriate framework for the study of certain phenomena in the astrophysical and the cosmological settings. This is motivated by a number of examples from cosmology and a brief discussion of some of the potential domains of its relevance in astrophysics.
The Present Status of the Munich Dust Counter Experiment on Board of the Hiten Spacecraft
Authors: Igenbergs E. , Hüdepohl A. , Uesugi K. , Hayashi T. , Svedhem H. , Iglseder H. , Koller G. , Glasmachers A. , Grün E. , Schwehm G. , Mizutani H. , Yamamoto T. , Fujimura A. , Ishii N. , Araki H. , Yamakoshi K. , Nogami K. 
Published: July 2016

AbstractThe Munich Dust Counter (MDC) is a scientific experiment on board the MUSES-A mission of Japan measuring cosmic dust. The satellite HITEN of this mission has been launched on January 24th, 1990 from Kagoshima Space Center. Here the present status of the MDC experiment is summarized. The number of dust particles measured so far is presented together with first and preliminary results of flux calculations and spatial as well as directional distributions of cosmic dust particles measured until July 25, 1990. A clear evidence of particles coming from the inner solar system (beta-meteoroids) already has been found. These are compared to particles coming from the apex direction.
Ultraviolet-Induced Amorphization of Cubic Ice and its Implication for the Evolution of Ice Grains
Authors: Kouchi A. , Kuroda T. 
Published: July 2016

AbstractWe found that cubic ice is transformed below 70 k to amorphous ice by ultraviolet irradiation, whereas no change in structure is observed at temperatures above 70 K, regardless of the irradiation time. Experimental results can be interpreted by theoretical consideration of nucleation and growth of cubic ice in amorphous ice. We also discuss the evolution of ice grains in space on the basis of the experimental results.
Simulation in Laboratory of Solid Grains Present in Space
Authors: Colangeli L. , Bussoletti E. , Mennella V. 
Published: July 2016

AbstractLaboratory data on cosmic dust analogue materials are compared with recent results obtained by means of spectroscopy and mass spectrometry on cometary dust, meteorites and interplanetary dust. Their actual chemical and physical properties can be further clarified, as well as possible links with interstellar dust.
Structures of Amorphous Silicate Dusts Simulated by Molecular Dynamics Method
Authors: Tsuchiyama A. , Kawamura K. 
Published: July 2016

AbstractAtomic structures of amorphous silicate dusts with the MgSiO3composition were simulated by molecular dynamics method as a function or the dust density based on the assumption that the density corresponds to cooling rate of dust formation. The SiO4tetrahedra are more polymerized with decreasing density, suggesting phase separation between SiO2-rich and MgO-rich components in less dense dusts formed by rapid condensation. A mode of atomic vibration probably due to the Si-0 bending is different in the amorphous silicates with different densities. This may cause changes of the 20 μm bands of IR spectra of silicate dusts with different cooling rates.
Measurement of Far-Infrared Absorption for Amorphous Silicates between 27 and 400 μm
Authors: Koike Chiyoe , Shibai Hiroshi 
Published: July 2016

AbstractThe far-infrared extinction of various silicates was measured in the 27 - 400 μm range of wavelength. The SiO2content of our samples distributes between 45 and 100 weight (wt.)%. There is no distinct absorption band in the far-infrared region and the extinction decreases in proportion toλ−1.4.
Interplanetary Dust Close to the Sun
Authors: Mann Ingrid 
Published: July 2016

AbstractThe optical and infrared brightness of the Fraunhofer-corona is produced by light scattering at the zodiacal dust particles and by their thermal emission (see Koutchmy and Lamy 1985). It is modelled within the ecliptic (4 Ro≤ ε ≤ 15 Ro)taking into account investigations of the global zodiacal dust cloud due to remote sensing and in situ experiments. The input of near solar dust to the corona brightness is discussed.
Future Observation of the F-Corona with the Lasco Coronograph Space Experiment
Authors: Lamy P.L. , Llebaria A. , Maucherat A. , Koutchmy S. , Giovane F. 
Published: July 2016

AbstractThe Wide-field White Light and Spectrometric Coronograph (LASCO) to be flown on SOHO in 1995 will observe the corona from just above the limb at 1.1 out to 30 solar radii (Ro). In addition to the fundamental problems of coronal physics (heating of the corona, acceleration of the solar wind, coronal transients), the scientific objectives incorporate the distribution and properties of dust particles including those released from sun-grazing comets, and interactions of coronal plasma with the dust.
The Scattering Matrix of Randomly Oriented Infinite Cylinders
Authors: Stammes P. 
Published: July 2016

AbstractA method is outlined to compute the scattering matrix of an ensemble of infinite cylinders in random orientation, as an approximation to the scattering matrix of an ensemble of very long but finite cylinders. Numerical checks are presented, which show that the results for infinite cylinders agree with theoretical results for very thick and very thin cylinders, as well as with numerical data for prolate spheroids and short finite cylinders.
The Micrometeoroid in the Upper Atmosphere
Authors: Kamijo F. 
Published: July 2016

AbstractThe temperature and the radius variation of micrometeoroids in the thermosphere and the mesosphere are calculated theoretically. If the radius and the initial velocity are 100μm and 30 km/sec respectively, the evaporation height and the velocity coincide almost exactly with those of the Capricornids and the Virginids from the meteor stream observation.Moreover, it is shown that the not evaporated debris till the end of the sublimation may become spherules in the bottom of deep sea; and that fluffy micrometeoroids (10μsize) floating in the stratosphere are also consistent with our calculation.The recondensation and the coagulation of the evaporated gas molecules from the meteoroid are also calculated, and it is shown that these secondary particles are very small and few.
The Annual Variation of Radio Meteor Echoes Observed from 1981 to 1985
Authors: Suzuki Kazuhiro 
Published: July 2016

AbstractThe radio observations of meteor echoes using FM broadcasting were carried out from January, 1981 to June, 1985. The annual variation of meteor rates in the 5 years was obtained from the observations made from 25h through 29h in local time (16h-20h UT).Some features in this annual variation can be explained by the occurrence of the major meteor showers. After the effects of these major showers are removed there remains a significant annual variation which shows higher rates in the winter half of the year (October to March). This seems to be caused by the annual variation of non-shower meteors radiating from the apex region.
The Taurid Complex: Giant Comet Origin?
Authors: Steel D.I. , Asher D.J. , Clube S.V.M. 
Published: July 2016

AbstractThe formation and evolution of the Taurid Complex of interplanetary objects is modelled on the basis of the parent being a giant comet which entered the inner solar system some time in the past 10,000-20,000 years. The orbital element distributions for the presently-observed meteor showers are discussed in terms of how these can constrain any model for the origin of the overall complex. As a baseline model we present results from the numerical integrations of fictitious meteoroids released from a comet over ten millenia, this comet having initial elements similar to those derived from a backwards integration of P/Encke. Large relative velocities at perihelion, above those feasible in conventional ejection scenarios, are necessary; we ascribe these to jetting of organics and other volatiles soon after release. Such a model gives a good first-order fit to the observed orbits, although additional processes (cometary splitting or asteroidal collisions) appear also to be necessary to explain the Taurids.
Characteristics of Interstellar and Circumstellar Dust
Authors: Tielens A.G.G.M. 
Published: July 2016

Abstract:This paper reviews our current knowledge of interstellar and circumstellar dust from an observational point of view. It is concluded that interstellar dust is highly heterogenous. It consist of a large number of different materials formed in a great variety of stellar birthsites under varying conditions and each with a highly isotopically anomalous composition in its main elements.
Chemical Composition of Dust Expected from Condensation Models
Authors: Yamamoto Tetsuo 
Published: July 2016

AbstractThis review examines to what degrees the present chemical equilibrium condensation models are effective in predicting chemical composition of grains observed in a variety of cosmic environments. The composition expected from the equilibrium calculations is reviewed separately for refractory (rocky and metallic) and volatile (icy) components. Comments are given on the limitation of the equilibrium calculations in predicting the grain composition. By taking cometary ice as a typical cosmic volatile condensate, it is pointed out that its composition is far from that expected from the equilibrium models. Theories on the formation of cometary volatiles are reviewed, and an observational clue helpful to testing the theories is pointed out. Discussion is given on the advantage for formation of organic materials from volatile solids.
The Source Composition of Galactic Cosmic Rays as Possibly Originated from the Dust in the Circumstellar and Interstellar Space
Authors: Sakurai Kunitomo 
Published: July 2016

AbstractThe chemical composition of galactic cosmic rays in their sources is similar to that of interstellar clouds or grains which are relatively enriched in refractory and siderophile elements as compared with the chemical composition of the solar atmosphere. Taking into account this fact, it is shown that the cosmic ray source matter can be identified as the dust or grains observed in the envelopes of red supergiant stars or the matter originally ejected from supernova explosions.
Radial Motions Near the Galactic Centre and the Origin of Galactic Spiral Structure
Authors: Schmidt-Kaler Th. 
Published: July 2016

The fundamental difficulty of explaining the spiral structure of galaxies by material arms is the winding dilemma which restricts the life-time of a spiral to about one rotation period. This dilemma is resolved by the density wave concept. However, the density waves are damped by various processes. We calculated the life time of the density wave for our Galaxy (τ = 8.108yrs) as well as for 24 nearby spiral galaxies with well-known data. It appears that the density wave can explain the existence of spiral arms for only about three rotation periods. After that time the energy of the wave has to be re-supplied. For this, various mechanisms have been proposed, e.g.1) tidal origin – which requires rather special circumstances2) resonant interaction – which is energetically insufficient3) local Jeans-type instability in the outer regions – which also may not be able to provide sufficient energy4) explosions of the nucleus – which involve high inclinations to the plane.
The Standard Solar Model
Authors: Bahcall J.N. , Cribier M. 
Published: July 2016

AbstractThe main features of standard solar models, the logic of the calculations, and some of the important results concerning solar neutrinos experiments are given. The input parameters that cause the greatest uncertainties in the calculated neutrino fluxes are the nuclear rection rates, the chemical abundances, the radiative opacity, and the equation of state. This article is based, with permission of the publisher, on Chapters 1 and 4 of Neutrino Astrophysics by J. N. Bahcall, Cambridge University Press (1989).
Comments on Solar Convection
Authors: Deubner Franz-Ludwig 
Published: July 2016

AbstractThis contribution discusses observational aspects of the evolution of individual structures of solar convection.It has been shown, that mesogranulation is a convective phenomenon that fits well into the gap between granulation and supergranulation. Apparently this observation justifies the view that the three members of the granulation family represent sections of a broad continuum of convective motions spanning the range of sizes from a yet unknown fraction of 1 Mm to about 50 Mm. Nevertheless, power spectra of velocity and brightness fluctuations exhibit three maxima, separated by intervals with significantly less power near 3 Mm and 7.5 Mm. Do these gaps give reasons for reconsidering the old idea, that each of the three characteristic scales has its own source layer at a certain depth in the convection zone?Power spectra of the granular energy distribution near the observational limit of spatial resolution suggest a continuous transfer of kinetic energy to smaller eddies by turbulent decay of the larger scale elements. Morphological studies of granular evolution and a comparison of the observed spectral line bisectors with theoretical predictions seem to disprove this idea. These observations imply either that the turbulent cascade, if it exists, is buried in the spatially unresolved part of the power distribution, or that radiative losses ultimately limit the life time of individual granules on all scales.
A Review of Observational Helioseismology
Authors: Duvall Thomas L. 
Published: July 2016

There have been several excellent reviews of observational helioseismology in recent years. These include the reviews by Harvey (1988), Libbrecht (1988), and van der Raay (1988) presented at a recent conference in Tenerife. The present effort will concentrate on the progress made on solar rotation recently.The Sun is a resonant cavity that supports many (~ 107) modes of oscillation. The modes that are most easily observed are the acoustic or p-modes. The eigenfunctions for these modes are:fnl(r) is the radial part of the separable eigenfunction where r is the radial coordinate measured from the center of the star. n is the number of radial nodes in the eigenfunction. Ylm (θ,ϕ) is the spherical harmonic function, where θ is the colatitude and ϕ is the longitude. The spherical harmonic degree l is the number of nodes of the spherical harmonic measured along a great circle that makes an angle with the equator. The azimuthal order m is the number of nodes around the equator. The frequency of the eigenmode, vnlm, depends on the mode. Much of our information derived about the solar interior from helioseismology comes from the measurement of these frequencies.
Magnetic Field in the Sun’s Interior from Oscillation Data
Authors: Dziembowski W.A. , Goode P.R. 
Published: July 2016

AbstractSolar oscillations provide a probe of the internal magnetic field of the Sun if the field has sufficient intensity. Using the oscillation data of Libbrecht, we find evidence for a 2 ± 1 megagauss quadrupole toroidal field centered at 0.7 of the solar radius which is barely beneath the base of the convection zone. This field, by its location and symmetry, may be associated with the dynamo that drives the Sun’s 22-year activity cycle.
Optical Studies of Classical Novae in Outburst
Authors: Seitter Waltraut C. 
Published: July 2016

AbstractA nova is followed optically from preoutburst to postoutburst appearance. Photospheric and atmospheric observational data are explained qualitatively through the energy budget, apparent in super-Eddington, Eddington, and sub-Eddington states, and the particle fluxes, according to their role in Grotrian’s model. In some instances, interpretations connected with Grotrian’s model are compared to results based on hydrostatic atmosphere models, for which quantitative versions exist. It is hoped that the physically and observationally sound ‘Ansatz’ of Grotrian may find followers to formulate an updated and extended theory.
Nova Ophiuchi 1988: 0.9–1.35 μm Spectroscopy
Authors: Lynch David K. , Rudy Richard J. , Rossano George S. , Erwin Peter , Puetter R. C. 
Published: July 2016

Near IR grating spectrophotometric observations (λ / Δλ ≃ 400 ) of Nova Ophiuchi 1988 between 0.9 and 1.35 μm on September 22.2, 1988 UT (J.D. = 2447426.7) are reported. We observed the nova with the Lick Observatory 3–meter Shane telescope using the Aerospace cooled grating spectrometer. A 7.5 arc sec aperture was used. The detector was a germanium photodiode, cooled to 77 K and used in conjunction with a charge integrating amplifier. These are the first IR observations ever made of a slow nova.Figure 1 shows the spectrum which contains Paschen emission lines β, γ δ, ε, ζ, η, He I λ1.083 μm, and a very weak continuum, all consistent with a post-maximum, early nebular phase. Figure 1 also shows a number of possible weak lines including [ Fe II ] and He I as well as an unidentified feature at 1.01 μm in the far red wing of Paδ. The line to continuum ratio for He I λ1.083 is about 300. The emission lines are resolved in the stronger features ( Paδ Paζ, Paβ, and He I λ1.083) and show a mean FWHM of 900 ± 150 km/sec.
HeI emission line formation in symbiotic stars and novae
Authors: Schmid H.M. 
Published: July 2016

The HeI triplet to singlet line ratio Λ = F(λ5876)/F(λ6678) in symbiotic stars and novae is often much lower than the planetary nebulae value of ≈ 3.5, which is also the low density value Λ0 predicted by recombination theory.Fig.1 shows that the dereddened HeI line ratios ^ are different for S type and D type symbiotic stars. The spectrophotometric data are mainly from Allen (1984, personal communication) and Blair et al.(1983). The S and D type classification divides the symbiotic stars according to the IR continuum into objects with a stellar continuum or dust emission. Practically all D types have low nebular densities Ne ≲ 107cm−3 and a rich spectrum of forbidden lines, while in S type objects these lines are suppressed by collisional deexcitation due to the high electron densities Ne ≳ 107cm−3. The observed HeI line ratio ^ in S type symbiotics, which is systematically too low when compared with the theoretical low density value Λ0 = 3.5, can therefore be attributed to the high nebular densities in these objects.
Classical Novae in the Context of the Evolution of Cataclysmic Binaries
Authors: Ritter Hans 
Published: July 2016

AbstractIn this paper we explore to what extent the TNR model of nova outbursts and our current concepts of the formation and secular evolution of cataclysmic binaries are compatible. Specifically we address the following questions: 1) whether observational selection can explain the high white dwarf masses attributed to novae, 2) whether novae on white dwarfs in the mass range 0.6M⊙ ≲ M ≲ 0.9M⊙ can occur and how much they could contribute to the observed nova frequency, and 3) whether the high mass transfer rates imposed on the white dwarf in systems above the period gap can be accommodated by the TNR model of nova outbursts.
The Theoretical Frequency of Classical Nova Outbursts as a Function of White Dwarf Mass
Authors: Politano Michael , Livio Mario , Truran James W. , Webbink Ronald F. 
Published: July 2016

Using the distribution of white dwarf masses in zero-age cataclysmic variables (CVs) calculated by Politano and Webbink (these proceedings), the relative frequency of classical nova outbursts as a function of white dwarf mass is calculated. These results are compared with the results obtained by Truran and Livio (1986), who calculated the same function, but used a distribution of white dwarf masses in CVs calculated from a Salpeter initial mass function and a particular progenitor mass-white dwarf mass relationship for single stars.We wish to calculate the frequency of classical nova outbursts as a function of white dwarf mass. To do this, we require two quantities: 1) the recurrence frequency of classical nova outbursts (i.e., how many outbursts per year) and 2) the white dwarf mass spectrum in classical novae (i.e., number of novae per white dwarf mass). We discuss each of these in turn.
Recurrent Novae
Authors: Webbink Ronald F. 
Published: July 2016

AbstractThermonuclear models of recurrent novae demand white dwarf accretors near the Chandrasekhar mass. In this case, the known recurrent novae should possess classical counterparts bearing the same structural parameters and space distribution, save for having only marginally less massive white dwarfs. Furthermore, recurrent novae should occur exclusively on ONeMg white dwarfs, and display in their ejecta either neon-group overabundances (if the white dwarfs are eroded through an outburst cycle) or no heavy element enhancements whatever (if the white dwarfs increase in mass).The known recurrent novae are reviewed in the light of these and other characteristics of thermonuclear runaway models, and also in terms of accretion-powered events, with special attention to the difficulties encountered by both models. Pivotal tests to distinguish between between thermonuclear and accretion models rely on the fact that the latter require far more mass transferred than the former to produce the same outburst energetics. Thus, photospheric opacities in thermonuclear recurrent novae are dominated by scattering; those in recurrent accretion events by true absorption. Orbital period changes through outburst are 103 times greater in accretion models than in thermonuclear models.
Possible X-Ray Flares in a Recurrent Nova
Authors: Hachisu Izumi , Itoh Hiroshi 
Published: July 2016

Abstract:The dynamical evolution and nonequilibrium X-ray emission of recurrent nova remnants have been investigated by using a spherically symmetric hydrodynamic code. We assume that the nova ejecta expand into a wind from a red-giant companion. The wind material is blast-shocked, and emits copious X-rays. The blast shock soon breaks out of the wind region and the X-ray emission declines drastically. The blast shock eventually catches up with the relatively slow ejecta of the previous outbursts. The X-ray emission may then be rejuvenated in both luminosity and spectral shape.