bluuebunny/crossref_metadata_2025_split huggingface dataset:
High Spatial Resolution Observations of the 1998 and 1999 Leonid Meteors
Authors: Jiang X.J. , Hu J.Y. 
Published: July 2016

AbstractWe observed the Leonid meteor storm in 1998 and 1999. The light curves extracted from the 2-dimensional images of the bright Leonid meteors clearly show the sub-structures, which are consistent with the generally accepted dustball meteor model (Hawkes & Jones, 1975).
Systematic Spectroscopic Observations on Small Telescopes: Past and Future Research of Stellar Kinematics
Authors: Sachkov M.E. , Glushkova E.V. , Rastorguev A.S. 
Published: July 2016

AbstractWe have used a CORAVEL-type spectrometer on small telescopes (70-cm, Moscow observatory, Russia; 60- and 100-cm, Simeiz observatory, Crimea, Ukraine and some others) for systematic observations of northern sky stars, since 1987 (Rastorguev & Glushkova, 1997; Gorynya et al., 1998). The typical accuracy of a single measurement is about 0.5 km/s. The limiting magnitude is 14 in V-band. The young Galaxy disk population, metal-poor stars and Kaptein selected areas are the important parts of our program. In this paper we present new results on galactic kinematics and our future program.
Deprojection of Planetary Nebulae
Authors: Zhang Z.W. , Ip W.H. 
Published: July 2016

AbstractUseful information can be obtained by deprojection of the two-dimensional images of extended objects such as planetary nebulae or supernova remnants. Three-dimensional distributions (assumed to be axially symmetric) of emissivity, electron number density and temperature might be derived from the deprojected structures. As a test, we follow the iterative algorithm of Leahy & Volk (1994) to project the images of several PNe taken at different wavelengths. This method can also be applied to the images of supernova remnants and galaxy clusters.
The Main Component Analysis of the Longitudinal Distribution of Solar Activity
Authors: Hejna Ladislav , Wöhl Hubertus 
Published: July 2016

Abstract In this contribution, preliminary results of the main component analysis of Bartels diagram of time series of daily values of sunspot group numbers for solar cycles 18, 19 and 20 are presented. The results obtained suggest that the most significant feature in the longitudinal distribution of sunspot activity is the existence of preferred solar hemispheres alternating with a mean period of 2.5 Bartels rotations.
Rotation of Large Scale Patterns on the Solar Surface as Determined from Filament and Millimeter Data
Authors: Pohjolainen S. , Vršnak B. , Teräsranta H. , Urpo S. , Brajša R. , Ruždjak V. , Jurač S. , Schroll A. 
Published: July 2016

AbstractThe rotation of large scale solar magnetic field patterns was studied using quiescent filaments and low temperature regions observed at 37 GHz as tracers.
The Boundary between the Magnetic Fields of Ap Stars and the Fields of Solar-type Stars
Authors: Landstreet John D. 
Published: July 2016

AbstractThe boundary between Ap-type magnetic fields and the magnetic fields of solar-type stars occurs near Te ~ 7000K, about where deep envelope convection develops in main sequence stars. This seems natural for solar-type stars, in which the field is generated by the convection zone. However, among magnetic Ap stars the frequency of occurrence declines from about 10% of all A stars near A0 to about 1% near F0. It is not clear what produces this decline in frequency, but the convection zone is probably not responsible. In fact, it seems likely that if global fossil fields occur in main sequence F stars, such fields should be detectable even if the stars having them are not chemically peculiar.
Spectroscopic Analysis of HR 1099
Authors: Savanov I.S. , Tuominen I. 
Published: July 2016

AbstractWe have calculated synthetic spectra for HR 1099 for the wavelength region λ6425-6445 Å, which includes the Cal λ6439 Å and FeI λ6430 Å lines, often used for the surface imaging of rapidly rotating late-type stars. The best agreement between the theoretical and observed spectra can be achieved with solar abundances in the both components of the system, except for Ca in the primary. Theoretical calculations give the possibility of estimating the influence of microturbulence, damping and blending on Ca I and Fe I line profiles.
The Rare Earths in the Peculiar A Stars: A Test Case for the Magnetic Diffusion Hypothesis
Authors: Shore Steven N. , Adelman Saul J. 
Published: July 2016

SummaryA brief formulation and an overview of the magnetic diffusion mechanism is presented. The atomic physics of the rare earth spectra is considered. It is demonstrated that basic differences among these elements contribute to the observed abundance anomalies of rare earth elements. The ion fractions of the rare earth display very different behaviour with temperature and pressure. In the atmospheres of Ap stars, europium tends to have the greatest degree of ionization. While previous studies on the diffusion mechanism with model atmospheres have maintained chemical homogeneity, we argue that this is an unrealistic approach to the Ap stars and present the consequences in the light of the diffusion picture.
The Influence of Light Variations on the Stellar Magnetic Fields Measurements
Authors: Catalano F.A. , Strazzulla G. 
Published: July 2016

SummaryIn the frame of the oblique rotator the radiation field is assumed to depend on the magnetic colatitude. Introducing this dependence in the effective magnetic field formula, a new expression for this has been derived.The calculations carried out in the case of a dipolar surface field having a polar intensity of 104gauss show that the amplitude of the variation and the polarity reversal both depend on the combination of the obliquity and inclination angles.
A High Dispersion Search For Peculiar A And B Stars
Authors: Dworetsky M.M. 
Published: July 2016

SummaryAll bright stars classified as normal B8-A0, luminosity class III, by Cowley et al. (1969) and Cowley (1972) have been examined on high dispersion spectrograms (10 and 20 Å/mm) obtained at Mt. Wilson in 1972 and 1973. Of 152 stars observed, 4 shell stars, 16 Hg or Hg-Mn stars, and 2 stars with other anomalies were found. Nine of these had previously been described as peculiar, although only four were in published sources at the time these observations were made.
Abundance Anomalies in am Stars and their Relation to Ap Stars
Authors: Khokhlova V.L. , Ptitsyn D.A. 
Published: July 2016

SummaryThe correlations of abundance anomalies of various elements in Am stars show continuous transition from normal through Am and Ap stars. There are poor correlations for some light elements and very good correlations for iron group and heavier elements. There is no obvious connection of the slope of correlation curves to ionisation potentials or opical term structure.
The Definition of the Terrestrial Coordinate Frame by Long Baseline Interferometry
Authors: Cannon W. H. , Rochester M. G. 
Published: July 2016

AbstractThis paper examines the question of the definition of the celestial and terrestrial coordinate frames by the technique of long baseline interferometry. It demonstrates how the celestial coordinate frame may be usefully defined in terms of basis 1-forms associated with the advancing phase fronts of the radiation fields from compact radio sources using only interferometer observables. The paper then proceeds to show how the terrestrial coordinate frame could be usefully defined, incorporating fully the effects of plate tectonics and secular motion of the observatories, by an application of the theory of continuum mechanics to interferometer observations.
The Effects of the Reference Frames and of their Realization on the Earth Rotation Parameters Computed from Different Observational Techniques
Authors: Capitaine Nicole , Feissel Martine 
Published: July 2016

AbstractThe inaccuracies in the reference frames actually realized by the different techniques for measuring the Earth’s rotation are theoretically investigated. The intercomparison of the available series of measurements provides numerical estimations of these defects. Using data corrected for reference frame effects high frequency fluctuations of UT1 are detected.
The Short Period Latitude Variations Derived from Recalculated Past ILS Observations
Authors: Manabe Seiji 
Published: July 2016

AbstractTen frequency components of short period latitude variations and corrections for the declination at an epoch and the proper motion in declination are estimated simultaneously. The short period variations are nearly diurnal and semi-diurnal and are supposed to be due to nutations and Earth tides. Analysis is by the least-squares chain method with weights for individual observations, recently developed by Manabe et al. (1977). Weights are assigned on the assumption that the observational errors follow a normal distribution, whose dispersion changes night by night. Among all possible 1024 combinations of the short period variations, the best is chosen on the basis of the minimum AIC procedure. The data used are the results of the homogeneous recalculation of the ILS observations, 1399-1978. This is considered to be the optimal astrometric data set for investigating nutations, because of its long time-span, homogeneity and size. Declinations are estimated for each of the seven observational periods with mean errors smaller than 001. The mean errors of the proper motions are of the order 0002/y. Among the short period variations, significant estimates are obtained for the terms corresponding to the lunar fortnightly, solar semi-annual and lunar nodal nutations, and the M2 tide. The mean errors are shown to be greatly reduced and the entire data set is analyzed. An effort is made to distinguish the preferred theoretical model.
Theoretical Evolution Sequences for Homogeneous and Two-Zone Models of Delta Scuti Variables
Authors: Andreasen G. Kjærgaard , Hejlesen P.M. , Petersen J. Otzen 
Published: July 2016

AbstractRadial pulsation periods are calculated for models of variables in the lower Cepheid instability strip. Evolution tracks in several diagrams are constructed and used for comparisons with observed periods, period ratios, and effective temperatures. These comparisons are simpler and more direct than in earlier studies with separate evolution and pulsation calculations.
Full Amplitude Models of 15 Day Cepheids
Authors: Cogan B.C. , Cox A.N. , King D.S. 
Published: July 2016

AbstractNumerical models of Cepheids have been computed with a range of effective temperatures and compositions. The amplitudes increase if the helium abundance increases or if the effective temperature decreases. The latter effect is contrary to observational data. The models also exhibit velocity amplitudes which are much lower than those observed.
Supernova Explosions - The Role of a Rayleigh-Taylor Instability
Authors: Buchler J. Robert , Livio Mario , Colgate Stirling A. 
Published: July 2016

AbstractA two dimensional hydrodynamic study indicates that convectively unstable gradients which develop during core collapse and bounce give rise to large scale core overturn. It is also shown that the concomitant release of neutrini can deposit large amounts of energy and momentum in the infalling envelope and give rise to a powerful supernova explosion.
Neutron Star Formation by Collapse of White Dwarfs
Authors: Canal R. , Isern J. , Labay J. 
Published: July 2016

Abstract.Mass-accreting carbon-oxygen white dwarfs become thermally and dynamically unstable when they reach high enough central densities. Carbon ignition at the star’s center likely propagates subsonically and, in the case of an initially solid core, leads to collapse if the rate of increase of the core’s mass is sufficiently fast. Recent results indicate, however, that solidification of the core induces carbon-oxygen separation. The central regions are then made of pure oxygen while carbon is rejected to lower-density layers. Carbon ignition happens only after neutronization of the central (oxygen) regions. Collapse to a neutron star is then independent from the rate of mass increase and the only possible restrictions are set by the behaviour of the outer, accreted layers. X-ray sources, pulsars and Type I supernovae are likely outcomes of this process.
Thermodynamic Transport Properties in Dense Stars
Authors: Edwards Terry W. 
Published: July 2016

AbstractThe thermodynamic transport properties of special relativistic imperfect fluids, as found in dense stars, are investigated. These properties, which include thermal and electrical conductivities, electrothermal coefficients, and bulk and shear viscosities may be formulated in terms of the momentum distribution functions obtained from the solution of the Boltzmann transport equation. Spherical harmonic solutions of the relaxation form of the relativistic magnetic Boltzmann transport equation have also been obtained which give the non-equilibrium momentum distribution function perturbation f-f(0) = Δf(p) in terms of electromagnetic and thermal fields.
The National Space Science Data Center (NSSDC) and the World Data Center A for Rockets and Satellites (WDC-A-R&S): Their Role in X-Ray Astronomy Data
Authors: Locke M. C. 
Published: July 2016

AbstractThe combined role of NSSDC and WDC-A-R&S in collecting, preserving and disseminating data from 10 years of X-ray observations is presented along with a brief history of the organizations.
The past and future of 1983 TB and its relationship to the geminid meteor stream
Authors: Fox Ken , Williams Iwan P. , Hunt J. 
Published: July 2016

AbstractIt is now well known that object 1983 TB, discovered by IRAS, has an orbit very similar to that of the Geminid meteor stream. Calculations show that this orbit crossed over the orbit of Venus about 500 years ago. We will describe calculations tracing the history of both the object and the stream through this interaction with Venus and the present interaction with the Earth.
The Interplanetary Micrometeoroid Flux and Lunar Primary and Secondary Microcraters
Authors: Zook H.A. , Lange G. , Grün E. , Fechtig H. 
Published: July 2016

AbstractWe are gaining an increased awareness and understanding of Earth-orbiting space debris. Meteoroid experiments in near-Earth orbit must therefore now be able to differentiate between interplanetary meteoroids and space debris. Space debris impacts are not thought, however, to have significantly affected near-Earth meteoroid measurements carried out in the early 1960’s. New experimental evidence also makes it appear very probable that most impact pits on lunar rocks with pit diameters smaller than 7 micrometers have been generated by lunar secondary ejecta impacts, and not by primary meteoroid impacts. In addition, ages determined from solar flare tracks in lunar rocks are not considered secure. Lunar crater production rates are more reliably deduced from meteoroid space experiments and not from solar flare track ages. When all of the above qualifications are taken into account, however, a rather satisfactorily self-consistent meteoroid flux versus mass distribution is obtained.
Optical Properties of Rough Grains: A Theoretical Study
Authors: Perrin J.M. , Lamy L. 
Published: July 2016

AbstractRecent work on the light scattering by large rough particles has led us to propose a model based on the high-energy approximation, the laws of geometrical optics and a mathematical description of the properties of the particle roughness. The influence of the various parameters of the model including those characterizing the roughness on the total intensity and the polarization is presented.
The Optical Properties of Circumstellar and Interstellar Dust in the Mid-IR
Authors: Pegourie B. , Papoular R. 
Published: July 2016

AbstractWe deduce the optical efficiency Q (λ)/ a of the circumstellar dust material over the range 8-30 μm from twelve M and G giants and supergiants and that of the dust present in the general ISM and molecular clouds from thirteen protostars. We then discuss the differences between these two profiles in the light of the condensation theory.
On the Dynamic Behaviour of Dust Striae Observed in Comets West 1976VI, and Mrkos 1957V
Authors: Kimura H. , Liu C.-P. , Jockers K. 
Published: July 2016

AbstractThe dynamic properties of the dust striae, observed in comets West 1976VI, and Mrkos 1957V, are reexamined in terms of the high speed emission model (HS model) proposed by Notni (1966). It is demonstrated that most striae can be well fitted to modified synchrones but this kind of fitting does not lead to a conclusive model; in most cases, the dynamic solution is not unique, and, furthermore, the derived high values of the ejection speed appear to be unrealistic, particularly for distant (or old) striae. The results suggest that the required initial velocity could be better interpreted as indicating the presence of nonradial acceleration.
Mass Input into and Output from the Meteoritic Complex
Authors: Grün E. , Zook H.A. , Fechtig H. , Giese R.H. 
Published: July 2016

AbstractDirect observations have established the size distribution of interplanetary meteoroids at 1 AU as well as the dependence of the spatial density with respect to the distance from the sun. After evaluating the consequences of mutual collisions and the effect of radiation pressure the following conclusions can be drawn: 1. Catastrophic collisions dominate the lifetimes of meteoroids with masses m ≳ 10−5g. About 10 tons per second are lost within 1 AU (mostly in form of 10−4g to 10−1g particles). Under steady state conditions these meteor sized particles have to be replenished by other sources, e.g. comets. 2. After being crushed by collisions 70 to 85% of this mass will be in form of particles with masses 10−10g ≲ m ≲ 10−5g. Part of these “zodiacal light” particles (about 0.3 tons per second) are transported by the Poynting Robertson effect towards the sun where they will evaporate. However, since the collisional production of these intermediate sized particles exceeds their losses this population is presently not in equilibrium. 3. 15 to 30% of the collisional fragments have masses m ≲ 10−10 g. Most of these small particles will be injected into hyperbolic orbits by radiation pressure (β-meteoroids).
Lorentz Scattering of Interplanetary Dust Grains
Authors: Barge P. , Pellat R. , Millet J. 
Published: July 2016

AbstractThe scattering of dust grains orbits due to recurrent sectors of the interplanetary magnetic field is reinvestigated with a better formalism. Our method reveals the resonant character of the diffusion and is well suited for the problem. The spreads in the orbital parameters are found less important than believed untill now and to vary rapidly with eccentricity and semi-major axis. Only the small dielectric grains with size less than 0.5 μm may be scattered by the Lorentz force fluctuations; the main diffusion occurs in inclination and near the sun (20-60 R⊙).
Determination of Absolute X-Ray Wavelength with the Double Reflection Method
Authors: Fraenkel Benjamin S. 
Published: July 2016

It has been shown that is is possible to determine absolute wavelength values of X-ray radiation emitted as a result of electron transitions in ions or atoms, without precise Spectrometers and without reference “lines”. Knowledge of the lattice constants of the diffracting crystal is sufficient for the determination of the wavelengths. Here the first experiment describing the feasibility of the method is shown.Usually spectra are obtained in form of “lines”. In the X-ray case, however, it is possible to obtain spectra in form of points, ordered along lines. The lines represent the white radiation [Fig. 1].
Inverse Inelastic Scattering Theory
Authors: Chuan Cao xuan 
Published: July 2016

For inverse scattering theories, it is well known that in order to guarrantee the existence and uniquness of the solution, drastic restrictions must be imposed on the scattering potential or on the scattering data collected from experiments (see for example Newton 1966). The existing theories in their original form such as the Geldfan Levitan or the Marehenko equations therefore cannot be used in a straightforward manner and some further steps toward simplifications have to be considered.In inelastic scattering problems where many coupled channels must be taken into account to construct various elements of the scattering matrix the problem become much more complicated both from the theoretical and experimental point of view. The present work deal only with the energy fixed case and show that a solution can nevertheless be obtained by using on one hand the conventional technique of the Abelian transformation which has been extensively applied in the JWKB approach to the one channel problem (see for example a general review by Buck 1971) with on the other some results obtained recently concerning a system of coupled differential equations (Cao 1982 1).
Introduction and Overview
Authors: Mihalas Dimitri 
Published: July 2016

The theme of this Colloquium is radiation hydrodynamics in and around stars and other compact bodies. To open our discussions, I would like to offer some rather elementary remarks about the role played by radiation in astrophysics.It is probably true that most astronomers view radiation primarily as a diagnostic tool. After all, the only access we have to astrophysical bodies (with a few exceptions inside the Solar System) is the photons we capture from them. And so an immense effort has been devoted to the development of techniques for converting raw information about the spatial, temporal, spectral, and polarization variation of the observed radiation field into knowledge about the physical structure of the object that produced the radiation. There are many difficult challenges, both observational and theoretical, to be met in this process, and the field is in a state of rapid development today, and will remain so for the forseeable future. Nevertheless, in the context of this conference it is worth emphasizing that in the diagnostic problem radiation plays an essentially passive role; it is merely the tool used to analyze the situation.
Jets From Young Stars
Authors: Mundt Reinhard 
Published: July 2016

AbstractRecent optical observations have shown that many young stars are capable of generating highly-collimated bipolar flows. Such flows are evident from narrow emission-line jets extending over 0.01-1 pc and having opening angles of a few degrees. Their measured radial velocities reach values of up to 400 km/s. For most known jets the “driving stars” are T Tauri stars or IR-sources of low to moderate luminosity (1-100 L⊙) . The typical velocities, Mach numbers, particle densities, and mass fluxes of these jets are estimated to be 200-400 km/s, 10-40, 15-150 cm−3, and 10−10−10−7 M⊙/yr, respectively. The estimated mass fluxes and velocities are consistent with our present knowledge of T Tauri star wind properties.The emission-line spectra of the jets are the same as observed in Herbig-Haro (HH) objects. Furthermore, the brightest parts of some jets (hot spots) are known as HH objects, having often been discovered many years before their associated jet. Thus, both phenomena are highly related and in both cases the emission lines are very probably formed in the cooling regions of shock waves with velocities of 50-100 km/s. There are a variety of mechanisms, which can in principal excite internal (oblique) Shockwaves in these jets. Examples of likely excitation mechanisms are fluid dynamical instabilities or pressure gradients in the ambient medium.A model is proposed in which HH objects are representing the locations of the most strongly radiating (internal)shock waves in these jets. For those HH objects being located at the end of the jet the observational data strongly suggest that they are tracing the working surface of the jet. This idea is consistent with the observed proper motions of these HH objects, the typical densities near the edges of their associated molecular clouds, and with the jet parameter given above. For a more detailed discussion of these jets the reader is refered to the review articles listed below.