bluuebunny/crossref_metadata_2025_split huggingface dataset:
Global and Photospheric Physical Parameters of Active Dwarf Stars
Authors: Pettersen B.R. 
Published: July 2016

AbstractPhysical parameters (temperature, luminosity, radius, mass and chemical abundance) of the photospheres of red dwarf flare stars and spotted stars are determined for quiescent conditions. The interrelations between these quantities are compared to the results of theoretical investigations for low mass stars. The evolutionary state of flare stars is discussed. Observational results from spectroscopic and photometric methods to determine the rotation of active dwarfs are reviewed. The possibilities of global oscillations in dwarf stars are considered and preliminary results of a photometric search for oscillation in red dwarf luminosities are presented.
The Structure and Energy Balance in Main Sequence Stars
Authors: Jordan C. , Ayres T.R. , Brown A. 
Published: July 2016

ABSTRACTHigh-resolution spectra obtained with the IUE satellite have been used to study the structure and energy balance in the main sequence stars ξ Boo A, α Cen A, α Cen B and ε Eri. The EUV observations are combined with X-ray fluxes to predict the coronal temperatures, the electron pressures and energy lost or transferred by radiation and thermal conduction
Late-Type Ca II Emission-Line Stars in the Southern Hemisphere
Authors: Collier A.C. 
Published: July 2016

ABSTRACTThe results of a photometric and spectroscopic study of twenty-three late-type southern stars with strong Ca II H and K emission are presented.The presence of photometric variability, with similar properties to the photometric wave phenomenon seen in the RS Canum Venaticorum binaries, is noted in thirteen of the fifteen stars for which extensive photometry was obtained. Of twenty stars for which high resolution radial velocity measurements were obtained, ten are found to be single-lined and seven are found to be double-lined spectroscopic binaries. The periods range from 0.66 up to 53-9 days.
Some Properties of Stellar Transition Regions
Authors: Saxner Mikael 
Published: July 2016

Among the strongest lines from stellar transition regions are the resonance lines of N V (1240Å), Si IV (1394 ,1403Å), and C IV (1549Å), which are all observable by the IUE.In an earlier paper (Saxner, 198l) it was noticed that there is a correlation between the fluxes in these three lines. In Fig. 1 the ratio of the N V to the C IV flux is plotted against the ratio of the C IV to the Si IV flux. Verbally the correlation may be stated as follows: the Si IV flux and the N V flux are covarying; if one is strong the other also tends to be strong, and vice versa. In all cases the C IV line is the strongest.
Synopsis of by Dra and II PEG Light Curves: Variability and Possible
Evidence of Differential Rotation
Authors: Rodonò M. , Pazzani V. , Cutispoto G. 
Published: July 2016

BY Dra (MOVe+MOVe) and II Peg (K2IV-III) are well known noneclipsing spectroscopic binary systems showing the low-amplitude quasiperiodic photometric variability that is typical of spotted stars.Since the discovery of their variability (Chugainov 1966, Eggen 1968) additional accurate photometry has been carried out (cf. Rodono 1982). On account of their highly variable light curves (LC), we have reanalyzed all the available observations and divided the original data into shorter time-interval sets, so that overlapping LCs with different shape could be separated. Additional LCs obtained at Catania Observatory till 198l were also included.
HK Lacertae
Authors: Olah Katalin 
Published: July 2016

HK Lac was observed at Konkoly Observatory between 1976-1981, the details of its story have been described in a previous paper (Olah, 1979).The aim of this investigation is to give a possible description of the strong variations in the light curve of the star.Searching for a more accurate period, it became obvious that the same period was not applicable to all the data. Therefore, a new period was derived for each different cycle by the Lafler-Kinman method. Unfortunately, due to the small number of data in the data sets these newly derived periods have an error of about 0.1 day.
Future Research Directions: Theoretical Approach and Perspective
Authors: Weiss N.O. 
Published: July 2016

AbstractIt is difficult to provide a comprehensive theoretical explanation for the activity of red dwarf stars. Among particular problems that are ripe for further investigation are: the production of steady, cyclic or irregular patterns of activity by nonlinear dynamo action in stars; the effect of magnetic buoyancy in producing photospheric magnetic fields; the formation of isolated flux tubes and their interaction with convection. These topics are discussed and some future lines of research are suggested.
High Order Resonances in the Evolution of the Lunar Orbit
Authors: Kovalevsky J. 
Published: July 2016

AbstractThis paper deals with the long term evolution of the motion of the Moon or any other natural satellite under the combined influence of gravitational forces (lunar theory) and the tidal effects. We study the equations that are left when all the periodic non-resonant terms are eliminated. They describe the evolution of the-mean elements of the Moon. Only the equations involving the variation of the semi-major axis are considered here. Simplified equations, preserving the Hamiltonian form of the lunar theory are first considered and solved. It is shown that librations exist only for those terms which have a coefficient in the lunar theory larger than a quantity A which is function of the magnitude of the tidal effects. The solution of the general case can be derived from a Hamiltonian solution by a method of variation of constants. The crossing of a libration region causes a retardation in the increase of the semi-major axis. These results are confirmed by numerical integration and orders of magnitude of this retardation are given.
The Study of Planetary Secular Perturbations
Authors: Jia-xiang Zhang 
Published: July 2016

SummaryThe methods of the first-order planetary secular perturbations are discussed in this paper. On the basis of Gauss' method, some concrete applicable formulae are derived. And then, orbital evolutions of the nine major planets in solar system during about 2,100,000 years are investigated numerically. The method applied here is in principle suitable for the orbits of arbitrary eccentricities and inclinations.
Physical Processes Affecting the Motion of Small Bodies in the Solar System and their Application to the Evolution of Meteor Streams
Authors: Williams Iwan P. 
Published: July 2016

AbstractIn addition to planetary perturbations, the small particles which make up a meteor stream are subject to outward radiation pressure and the Poynting-Robertson effect. New particles can also be generated in a stream through being released from the nucleus of a comet. We summarise the main physical effects, discuss models for meteor stream evolution and give a brief account of the observational data available.
Analytical Theory of A Trapping. In A Two-Body Problem of Variable Mass
Authors: Omarov T.B. , Minglibaev M.J. 
Published: July 2016

SummaryThe new nonstationary model problem is considered. Its solution generalizes by form the known particular Mestschersky-Vinti solution in a two-body problem of variable mass. The equations of the corresponding perturbed motion are deduced. In the case of a two-body problem of variable mass μ. the perturbing force is proportional to second temporal derivative from the value μ-1 . It is possible to describe with a good approximation such qualitative effects in this problem as a trapping and disintegration on a basis of properties of the model problem. Let us consider the example of a trapping.
Degenerate Dynamical Systems and the Disappearance of (K.A.M.-Type) Integrals of Motion
Authors: Varvoglis H. 
Published: July 2016

ABSTRACTThe problem of constructing the stochasticity criterion of a degenerate near-integrable dynamical system is considered. We show that in certain cases the above criterion can be found as the limit of the corresponding stochasticity criteria of a family of non-degenerate systems, whose limit is the degenerate one.
UV line emission of symbiotic stars
Authors: Nussbaumer H. 
Published: July 2016

AbstractGeneral characteristics of emission line spectra from symbiotic stars are outlined. Data from some special line ratios in the 1000 Å - 3000 Å range, and others connecting the visual and the far UV lines are presented, and their application to symbiotic stars is discussed. Integrated fractional abundances for ions easily observed in the far UV are given to facilitate abundance determinations for nebular conditions. It is found that the physical conditions of the regions emitting the emission line spectra differ considerably among different symbiotic stars.
X-ray observations of symbiotic stars
Authors: Allen David A. 
Published: July 2016

AbstractObservations are reported of 19 symbiotic stars made with the imaging proportional counter of the Einstein Observatory. Three of the objects (HM Sge, V 1016 Cyg and RR Tel) were detected as soft X-ray sources. All three have shown slow-nova eruptions in the past 40 years. The data are interpreted as support of a model for slow novae involving thermonuclear events on white dwarfs which accrete from M giant companions. Symbiotic stars in their steady state, not being detected X-ray sources, are presumed to be powered by the accretion process alone.
Variation spectrale de CI Cygni en 1975
Authors: Fehrenbach Ch. 
Published: July 2016

En 1971 et 1972, cette étoile présentait un spectre d’émission comorenant des raies de l’hvdrogène et les métaux ionisés Call. Fell, etc… se superposant sur un fond continu sans raie d’absorption, [Fell] est présent par deux raies faibles, les raies de l’hydrogène, de Fell et de CrII présentaient un profil P Cyg.Le 4 Juillet 1975, Madame Y. Andrillat a sienalé la disparition de la raie de Hel 10830. Nous avons obtenu immediatement un spectre à 20 A mm-1 au télescope de 152 cm. Ce spectre est un spectre d’absorption où seules les raies de l’hydrogène présentent des émissions à structures complexes.
Changes of LISM Characteristics in the Heliospheric Interface
Authors: Ripken Hartmut W. , Fahr Hans J. 
Published: July 2016

AbstractIt is possible to deduce LISM properties from observations of interstellar neutral gases in the inner solar system. Parameters accessible by this method are the interstellar wind vector and the densities and temperatures of hydrogen and helium, implying also the deduction of the relative abundance ratios and the degree of ionization in the LISM. Direct inference from observations, for example resonance luminescence measurements of Ly-alpha and He-58.4 nm radiation, yields values appropriate only for the inner solar system, i.e. for the regions within the heliopause dominated by the solar wind plasma.Particularly the subsonic LISM plasma interface ahead of the heliopause causes profound changes in the properties of the neutral LISM gas traversing this region. Mainly p-H charge exchange processes give rise to the destruction of primary hydrogen and the production of secondary hydrogen atoms, the net effect being a depletion of the neutral hydrogen component of the LISM by about 50%.Details on the depletion mechanisms, the hydrogen and oxygen extinctions, and the consequences for the Ly-alpha resonance luminescence intensity interpretations are presented.
Inverse Relations between 0.25 keV counts and local interstellar dust
Authors: Knude J. , Jakobsen P. , Labov S. , Bowyer S. 
Published: July 2016

A preliminary comparison of color excesses and HEA0-1, A2 0.25 keV counts have been performed on two angular levels in order to search for indications of local photoelectric absorption.a. Color excesses and background counts are smoothed to a common 1.5 1.5 sq.deg. beam. Although distance information on the color excesses are available it is not used in this first attempt. The lines of sight to which the excesses pertain have however a length comparable to the expected viewing distance at these energies in the local medium. Figure 1 displays the resulting average counts/pixel versus average excess/pixel for the five areas investigated. A general decrease of the counts with excess is apparent. The wide scatter in the individual regions is probably due to excess variations on scales smaller than the collimated beam. The minimum counts on the diagram come from a region where an almost coherent sheet of dust is present within a distance ~200 pc. The constancy of the minimum counts in this particular direction indicates that the soft X-ray emission probably originate exclusively in front of the matter observed to be present. Note that the SGP counts show a shallow inverse dependence on excess. The latitude distribution of the five areas assures that the general inverse relation of the 0.25 keV counts on color excesses is not a latitude effect.
The Parallax of Pulsar 0950+08 and the Local Free Electron Density
Authors: Gwinn C.R. , Taylor J.H. , Weisberg J.M. , Rawley L.A. 
Published: July 2016

AbstractWe report a parallax of 7.9±0.8 mas for PSR 0950+08, corresponding to a distance of 130±15 pc. The measured pulse dispersion of this pulsar implies an average free electron density of 0.023±0.002 cm-3 along the line of sight. This parallax measurement is subject to systematic errors and questions of interpretation which have not yet been fully explored.
A New Halo Survey
Authors: Carney Bruce W. , Latham David W. 
Published: July 2016

AbstractWe describe a new survey of proper motion stars now nearing completion. We briefly discuss the survey’s completeness and our data analysis methods. We present preliminary results for the motion of the Local Standard of Rest (LSR) with respect to the most extreme velocity stars and the possible presence of a metallicity gradient amongst the halo stars.
The Hyades: Membership and Convergent Point from Radial Velocities
Authors: Stefanik Robert P. , Latham David W. 
Published: July 2016

AbstractMultiple radial velocities of 212 proper motion and/or photometric Hyades candidates have been obtained in the magnitude range 5 < V < 15 with an accuracy of ± 0.7 km s−l for an individual observation. These observations have been used to establish cluster membership, to identify binary star candidates, to derive a convergent point solution and to determine the cluster distance.
Internal Dynamics of Globular Clusters
Authors: Freeman K.C. 
Published: July 2016

The purpose of this review is to discuss why stellar radial velocities are so important for globular cluster dynamics.Globular clusters are structurally fairly simple. They are almost spherical and almost entirely stellar. Hany of them are close enough to allow really detailed observations of their stellar content, structure and internal motions. They give us a unique opportunity to acquire an understanding of the present dynamical state of real self-gravitating systems of interacting stars, at a level of detail that will probably never be possible for any galaxy. This would be an excellent starting point for the theory of the formation and dynamical evolution of globular clusters, which is now a very active area of research.
Dynamics of NGC 188
Authors: Harris Hugh C. , McClure Robert D. 
Published: July 2016

AbstractRadial velocities have been obtained of 48 stars (33 member giants) in NGC 188 to investigate the internal dynamics. The velocity dispersion drops from the center outward, but the observed central dispersion is undoubtedly inflated by undetected binaries. The binaries concentrate toward the center, but models of the binary population show that corrections for their effect on the dispersion of any small sample are uncertain. The dispersion in the outer ring indicates a cluster mass in agreement with the mass of visible stars.
Coravel Measurements of IAU and Southern Potential Radial-Velocity Standard Stars. A Zero Point Discussion
Authors: Mayor M. , Maurice E. 
Published: July 2016

AbstractRadial velocity measurements have been carried out since 1981 with the spectrometer CORAVEL at ESO, La Silla. Almost one thousand measurements of IAU radial velocity standard stars and of potential southern standard stars have been acquired by the different observers (mean precision per measurement 0.2 km/s).Among the measured IAU standard stars, at least four have shown clear radial-velocity variations from 1981 to 1984 (HD 36673, 156014, 44131, 115521).The comparison between CORAVEL mean velocities and IAU values reveals a difference of approximately 0.8 km/s between bright (mv <4.3) and faint IAU (mv >4.3) standards (Vr(IAUB) - Vr(IAUF) = +0.8 km/s). A similar difference also appears when comparing IAU standard velocities and those measured with the Victoria spectrometer, Fletcher et al. (1982).Thus, IAU standard stars not only include radial-velocity variable stars (intrinsic variables and SB) but they also present zero-point systematic effects.In the present paper we correct the radial velocities of the bright IAU standard stars so that they now belong to the same system as the faint ones. After elimination of variable velocity stars and stars showing large differences between IAU values and recent radial-velocity determinations, an homogeneous list of 34 IAU standard stars is obtained. These revised radial velocities are based on IAU values and new determinations obtained with the Victoria spectrometer and with CORAVEL at La Silla. These stars are distributed between the declinations δ = -82° and δ = +28°.This paper uses observational data in advance of the publication by CORAVEL observers of the 7th of the series of papers: “Radial velocities of southern stars obtained with the photoelectric scanner CORAVEL”.
Stellar Lineshifts Induced by Photospheric Convection
Authors: Dravins Dainis 
Published: July 2016

AbstractEffects of stellar atmospheres on measured radial velocities are examined. Surface convection (“stellar granulation”) causes photo-spheric line asymmetries and wavelength shifts of ≃ 100 - 500 m/s. Cyclic changes in the convection patterns, such as observed during the solar 11-year cycle, may mimic radial velocity variations of perhaps 30 m/s. The study of stellar atmospheres would benefit from accurate (< 100 m/s) differential radial velocity measurements among lines of different parameters (strength, excitation potential, wavelength region) in the same star. To minimize convective perturbations, the flanks of very strong photospheric lines should probably be used, at least in stars with weak chromospheres. To disentangle cyclic variations due to stellar motion, several different groups of lines should be monitored, together with the Ca II K chromospheric emission.
DDO Standard Velocity Star Measures 1968–1984
Authors: Kamper Karl W. 
Published: July 2016

The current Cassegrain spectrograph on the DDO 1.9m telescope was first used in 1966, but came into regular service in 1968. It is a fairly standard configuration with a Cassegrain collimnator and f/2 and f/5 Schmidt cameras. In practice, the f/5 camera with gratings which yield dispersions of 8A/mm and 12A/mm In the blue have been used almost exclusively, with the latter the more common. Interchangeable red- and blue-enhanced collimnators and Richardson image slicers were added in June, 1978.More than 1200 plates of IAU standard velocity stars have been taken with this spectrograph, of which measures of 956 were made by us, or were available from the DDO archives or were made available by other investigators. Ten of these plates were not used because they were taken with unusual grating and tilt combinations. Some of the plates left unmeasured were simply broken or of poor quality, but a depressingly large number were simply missing. Most of the stars of spectral type M have also not been measured, since a line list for this class has only recently been created. Of the plates used in this study 810 were with the 12A/mm dispersion, 110 with the 8A/mm, and 26 were taken at 16A/mm in the red. The latter are of less use in studying the IAU stars themselves, but are essential in calibrating the rather considerable number of velocities measured here in the red.
Bibliographic Catalogue
Authors: Barbier M. 
Published: July 2016

The increasing number of stellar radial velocity determinations and their publication in many journals necessitates the compilation of a continuously evolving bibliographic catalogue.The first stellar radial velocity catalogue was compiled by H. A. Abt and E. S. Biggs in 1972. It is complete up to 1970. At the Marseille Observatory, Mme. M. Petit and myself have undertaken a follow-up of this catalogue. Our presentation is nearly the same.We systematically examine all reviews of possible interest received in our library. Our bibliography does not include papers which do not publish new data on radial velocities. The first part of our catalogue, including about 5000 references between 1970 to 1975, was published on microfiche in 1979. This microfiche was prepared by the Strasbourg Stellar Data Center. The catalogue is available on magnetic tape from the Stellar Data Center. This first part was not complete and several corrections have been made.
Mass Distribution and Luminosity Function of White Dwarfs
Authors: Weidemann Volker , Yuan Jie W. 
Published: July 2016

Ever since Graham’s Strömgren photometry (1972) demonstrated the existence of a single well defined cooling sequence of DA white dwarfs the question of the mass dispersion (or the width of the number-mass distribution) has been in the foreground of my studies (Weidemann, 1970, 1977).Indeed it turned out that the shape of the white dwarf mass distribution provides strong constraints on the theory of stellar evolution with mass loss, a fact which will be demonstrated again in the following lecture. It therefore seems worthwhile to dwell in some detail on the methods of its determination. For the benefit of the non-specialists I shall first present some of the historical results and then continue to discuss the present situation.
Transport Processes and Neutrino Emission Processes in the Interior of White Dwarfs
Authors: Itoh Naoki 
Published: July 2016

AbstractRecent developments in the studies of the transport processes and the neutrino emission processes in the interior of white dwarfs are reviewed. Special emphasis is placed upon the accuracy of the calculations. Ionic correlation effects play an essential role in the transport processes and the neutrino bremsstrahlung process. The Weinberg-Salam theory is the basis for the calculation of the neutrino emission processes.
Rosat - An All-Sky X-Ray and EUV Survey of White Dwarfs
Authors: Barstow M.A. 
Published: July 2016

AbstractThe West German astronomy satellite ROSAT comprises two imaging telescopes - an X-ray instrument covering the energy band 0.15-2keV and an EUV instrument (provided by the UK) covering the range 0.02-0.21keV. A primary aim of the mission is to perform a sensitive all-sky survey with both telescopes (two ‘colours’ in the EUV) in the first 6 months. This will be followed by a least one year of pointed observations at specific targets. This paper briefly describes the ROSAT instrumentation and discusses the likely impact of the survey on white dwarf studies.