bluuebunny/crossref_metadata_2025_split huggingface dataset:
A Type Stars as Probes of the Local Interstellar Medium
Authors: Ferrero R. Freire , Ferlet R. , Vidal-Madjar A. 
Published: July 2016

AbstractWith the aim to sample well the Local Interstellar Medium (LISM),we propose to use A stars as targets. The Mg II UV lines seems to be the best interstellar absorption candidates. Several hundreths of A stars can be reached within 100 pc. First preliminary results (20 lines of sight) are presented, based on previous Copernicus and actual IUE observations.
Distances of Local Clouds from Optical Line Observations
Authors: Crutcher Richard M. , Lien David J. 
Published: July 2016

AbstractWe observed the interstellar D-lines of Na I toward 49 stars in order to determine the distance (125 ± 25 pc) to a cold H I cloud. This sheet of gas may be part of the back side of the shell formed by the Loop I supernova.
Absorption and Emission of EUV Radiation by the Local ISM
Authors: Paresce Francesco 
Published: July 2016

AbstractThe Berkeley EUV telescope flown on the Apollo Soyuz mission in July, 1975 established the existence of a measurable flux of EUV radiation (100 ≤ λ ≤ 1000 Å) originating from sources outside the solar system. White dwarfs, flare stars and cataclysmic variables were discovered to be relatively intense compact sources of EUV photons. Moreover, this and other subsequent experiments have strongly suggested the presence of a truly diffuse component of the EUV radiation field possibly due to thermal emission from hot (T > 105 K) interstellar gas located in the general vicinity of the sun (r ≃ 100 parsecs.) Closer to the HI, 912 Å edge, the effect of a few hot O and B stars has been shown to be very important in establishing the interstellar flux density. All these results imply that the local ISM is immersed in a non-negligible EUV radiation field which, because of the strong coupling between EUV photons and matter, will play a crucial role in determining its physical structure. Conversely, of course, the local ISM is expected to leave a strong imprint on the EUV field reaching the terrestrial observer.The objective of this review will be to assemble and critically analyze the available information on the local ISM derived from the limited EUV observations carried out so far. These include measurements of the spectra of bright EUV sources that reveal clear evidence of H photo absorption at λ > 400 Å and of the He ionization edge at 228 Å. The EUV diffuse background is found to convey interesting information on the density, temperature and possible location of the hot ISM component that can be profitably compared with similar data on far uv absorption lines, principally OVI. The results discussed in this context will be shown to be quite useful in illuminating the path that future EUV sensitive observatories such as EUVE and Columbus might profitably follow in the near future.
Magnetic Alignment Theory and the Interpretation of Polarization
Authors: Cugnon Pierre 
Published: July 2016

AbstractThis paper presents some reflexions about the theory of magnetic spinning alignment. It is shown that a classical enhanced thermal Davis and Greenstein mechanism may be considered as a limiting case of Purcell's suprathermal spinning alignment theory when the number of active sites on a given grain becomes very important and/or for very short-lived suprathermal sites.This result is applied to the interstellar medium and some problems in which it may be important are briefly discussed, with special attention to local implications.
Dark Matter Near the Sun: Simulated Star Counts and the Oort Limit
Authors: Gilden David , Bahcall John N. 
Published: July 2016

AbstractAn ensemble of orbits passing through the solar position have been generated for a specific mass model of the galaxy. These orbits are randomly sampled to form simulated density distributions of tracer stars perpendicular to the galactic disk. The simulated distributions are analyzed in order to determine the sampling errors in a self-consistent derivation of the total amount of matter near the sun (the Oort limit).
Stellar Radial Velocities of High Precision: Techniques and Results
Authors: Campbell Bruce , Walker G.A.H. 
Published: July 2016

AbstractRelative radial velocities can now be determined with internal errors as small as ~ 10 m s−l. A variety of techniques for achieving this level of precision are either presently running, or will soon be on-line. These could be used on several astronomical frontiers; the most demanding application is the search for extra-solar planetary systems. We briefly review these techniques, and highlight the results obtained to date.
Radial Velocities for the Hipparcos Program
Authors: Duflot M. 
Published: July 2016

The studies by Fehrenbach show that objective prisms with normal fields are well adapted to a statistical study of stellar motions in our galaxy. Now, thanks to computers we can easily reduce the plates. Since the beginning of 1982 we have been engaged in obtaining radial velocities for the stars (m < 9.0) in the Hipparcos Input Catalogue. We have chosen fields with a large number of stars with spectral types earlier than F5 and with unknown radial velocities. However, in a given field we measure all of the stars.In Table I we list our instruments and the stars for which they are used.
Largescale Problems of Galactic Structure and Dynamics
Authors: Freeman K.C. 
Published: July 2016

In tills review, I will talk about some galactic problems for which stellar radial velocities are important. I will not attempt to be comprehensive, but will just pick out some problems which are being actively studied and which I find particularly interesting.This is a classical problem. The aim is to estimate the total matter density near the Sun from the distribution and kinematics of a tracer population towards the galactic poles. Recently Bahcall (1984a,b,c) has made a major attack on this problem, using F stars and W giants. He finds that about half the total matter density near the Sun is unaccounted for. This is important. We know from work on other diek galaxies that about half their mass lies in a dark corona and the other half in the disk; the nature of this dark matter is not yet understood. If we also see that about half the mass of the disk itself is dark, then that is certainly worth knowing, because this dark matter has dissipated to the disk. That may help us to understand the nature of the dark matter.
A Search for Halo Binaries: the First Results
Authors: Latham David W. , Stefanik Robert P. , Carney Bruce W. 
Published: July 2016

AbstractHe report the first results from a program to monitor the stars in the Carney and Latham (1985) halo survey for velocity variations due to orbital motion. From the sample of 300 stars with high space velocities, 24 spectroscopie binaries candidates have been identified.The Halo Survey of Carney and Latham (1985) has identified approximately 300 stars with space velocities greater than 200 km sec−l compared to the local standard of rest. The radial velocities of these stars have been monitored for typically two years, and at least 24 show evidence of possible variation. These stars are listed in Table I, which gives the star name, the number of observations, the number of days between the first and last observations, the mean velocity, the RMS, the U, V, and W velocities, and the speed compared to the galactic rest frame.The error of a single measurement is perhaps ± 0.7 km sec−1, but depends to some extent on the metallicity and the quality of the spectrum. For a star to be included in Table I as a binary candidates we have chosen a threshold of ± 2.0 km sec−1 for the RMS, or approximately 3 sigma. We plan to monitor the radial velocities of these binary candidates closely over the next few years. We also plan to obtain b-y and V-K colors to search for the light of possible companions.
A Determination of the Radial Velocities of Galaxies
Authors: Popov V.S. , Polyakova G.D. 
Published: July 2016

Fourteen galaxies were studied using 24 spectra, obtained with the 6 meter telescope of the Special Astrophysical Observatory of the USSR Academy of Sciences. The dispersion of the spectrograph in the primary focus of the telescope was 189 A/mm.The neon spectrum was studied in order to determine the wavelengths of the comparison spectrum and to plot a dispersion curve. The following Ne I lines were used for a comparison: 6143, 6266, 6506, 6678, 6717, 6929 and 7032 A. In galactic spectra (wavelength range of 4300 - 7000 A) 21 absorption lines were detected. They belong to H, Na I, Ca I, Ca II, Mg I and otner chemical elements. Three emission lines of the night sky with wavelengths of 5577, 5890 and 6300 A are seen in the spectra of galaxies. They were also used as reference lines for our determination.
Two New Faint Common Proper Motion Pairs
Authors: Ruiz María Teresa , Maza José 
Published: July 2016

AbstractSpectrophotometry of the common proper motion pairs ES0439-162/163 and ESO440-55a/55b shows that the first is formed by an mv =18.8 magnetic DQ white dwarf and an mv = 19.8 DC9 white dwarf separated by 23”. ESO440-55a/55b has an mv = 20.2 red dwarf (ST=M5.1) component and a DZ7 white dwarf with mv = 19.3, their angular separation being The proper motion of the pairs is μ=0.38±0.03”/year and μ=0.22±0.04”/year respectively.
Far Ultraviolet Observations of Hot DA White Dwarfs
Authors: Finley David , Basri Gibor , Bowyer Stuart 
Published: July 2016

AbstractFar ultraviolet (FUV) fluxes have been used for determining the effective temperatures of a number of DA white dwarfs hotter than 20,000 K. The spectra were obtained with the International Ultraviolet Explorer (IUE). The analysis consisted of comparing the observed FUV fluxes with model fluxes scaled to the V-band flux. After suitable corrections were performed for the time-dependent sensitivity degradation of the IUE, it was found that the available flux calibrations for the IUE were insufficiently accurate for precise temperature determinations. Accordingly, we used seven white dwarfs for which accurate, independent temperature determinations have been made from line profile analyses to improve the accuracy of the IUE flux calibration. The correction to the original calibration was as great as 20% in individual 5-Å wavelength bins, while the average over the IUE wavelength range was 5%. We present both our IUE flux correction and the temperatures obtained for the hot white dwarfs.
The Effect of CNO Metal Abundances on the Soft X-Ray Emission from He Rich White Dwarfs
Authors: Barstow M.A. 
Published: July 2016

AbstractPredicted soft X-ray fluxes for model atmospheres containing varying concentrations of CNO metals are compared with those observed by EXOSAT for the planetary nebula nucleus K1-16. An effective temperature in the range ≈ 125000 − 180000K is determined for K1-16 and a limit on the concentration of CNO in the atmosphere (between 0.02 and 20 ×solar relative to He) obtained. Some comments on the application of the models to the apparently metal rich star H1504+65 are included.
Cooling of White Dwarfs with Account of Non-Equilibrium Beta-Processes
Authors: Bisnovatyi-Kogan G.S. 
Published: July 2016

Non-equilibrium heating of white dwarfs during two-step neutronization and formation of small but finite core of the new phase is a main source of energy in these stars when the temperature is sufficiently small and Coulomb crystal becomes degenerate.Existence of Chandrasekhar mass limit of white dwarfs Mch = 5.83 /μ2z, μz = A/z, is connected with the prevalence of the relativistic degenerate electrons in pressure. When neutronization is taken into account, the maximal value of mass is smaller and is reached at finite density (Schatzman, 1958). The central density of the white dwarf with limiting mass is larger than threshold density of neutronization. Such star has a small, but finite core of new phase (Seidov, 1967). The neutronization threshold for the iron is equal to ρ = 1.15 109 g/cm3 The neutronization goes through two steps
Polarized Radiation from Inhomogeneous Accretion Columns in AM Herculis Binaries
Authors: Wu Kinwah , Chanmugam G. 
Published: July 2016

AbstractThe polarization of radiation emitted by inhomogeneous accretion columns is found to be significantly different from homogeneous columns. A good fit to the V-band circular polarization light curve of EF Eri is obtained using the two-core model with temperature &T=15keV, magnetic field B=26MG, and dimensionless plasma parameter Λ ≤ 106.
The White Dwarf Mass and Orbital Period Distribution in Zero-Age Cataclysmic Binaries
Authors: Politano M. , Webbink R. F. 
Published: July 2016

A zero-age cataclysmic binary (ZACB) we define as a binary system at the onset of interaction as a cataclysmic variable. We present here the results of calculations of the distributions of white dwarf masses and of orbital periods in ZACBs, due to binaries present in a stellar population which has undergone continuous, constant star formation for 1010 years.Distributions of ZACBs were calculated for binaries formed t years ago, for log t = 7.4 (the youngest age at which viable ZACBs can form) to log t = 10.0 (the assumed age of the Galactic disk), in intervals of log t = 0.1. These distributions were then integrated over time to obtain the ZACB distribution for a constant rate of star formation. To compute the individual distributions for a given t, we require the density of systems forming (number of pre-cataclysmics forming per unit volume of orbital parameter space), n£(t), and the rates at which the radii of the secondary and of its Roche lobe are changing in time, s (t) and L, s (t), respectively. In calculating nf(t), we assume that the distribution of the orbital parameters in primordial (ZAMS) binaries may be written as the product of the distribution of masses of ZAMS stars (Miller and Scalo 1979), the distribution of mass ratios in ZAMS binaries (cf. Popova, et al., 1982), and the distribution of orbital periods in ZAMS binaries (Abt 1983). In transforming the the orbital parameters from progenitor (ZAMS) to offspring (ZACB) binaries, we assume that all of the orbital energy deposited into the envelope during the common envelope phase leading to ZACB formation goes into unbinding that envelope. R.L, s (t) is determined from orbital angular momentum loss rates due to gravitational radiation (Landau and Lifshitz 1951) and magnetic braking (γ = 2 in Rappaport, Verbunt, and Joss 1983). We turn off magnetic braking if the secondary is completely convective.
The Optical Spectra of V803 CEN
Authors: Kepler S.O. , Steiner J.E. , Jablonski F. 
Published: July 2016

AbstractWe obtained spectrophotometry of V803 Cen in both high state (B ≈ 13.5) and low state (B ≈ 17) from 3800 Å to 7100 Å and 5 Å resolution. Essentially all the observed absorption lines are due to He I. No emission lines in either high or low state were detected, as well as no significant departures from a Planck law distribution.
The Mass Spectrum of the White Dwarfs in Cataclysmic Binaries
Authors: Politano M. , Ritter H. , Webbink R. F. 
Published: July 2016

AbstractUsing the theoretically predicted mass spectrum of the white dwarfs (WDs) in zero-age cataclysmic binaries (ZACBs) by Politano and Webbink (1988), we examine to what extent observational selection can account for the observed high masses of the WDs in cataclysmic binaries (CBs).
Growth Rate of White Dwarf Mass in Binaries
Authors: Kato Mariko , Saio Hideyuki , Hachisu Izumi 
Published: July 2016

AbstractThe growth rate of a white dwarf which accretes hydrogen-rich or helium matter is studied. If the accretion rate is relatively small, unstable shell flash occurs and during which the envelope mass is lost. We have followed the evolutions of shell flashes by steady state approach with wind mass loss solutions to determined the mass lost from the system for wide range of binary parameters. The time-dependent models are also calculated in some cases. The mass loss due to the Roche lobe overflow are taken into account. This results seriously affects the existing scenarios on the origin of the type I supernova or on the neutron star formation induced by accretion.
Trapezium Type Multiple Systems and Formation of Stars
Authors: Salukvadze G.N. 
Published: July 2016

AbstractBy a comparison of Trapezium-type multiple star systems in the Abastumani Catalogue and the famous Catalogue of Stellar Associations and Clusters, it is confirmed that the great number of Trapezium-type multiple stars, which belong mostly to spectral classes 0-B2, are found in associations and clusters.In 13 T-associations, 120 Trapezium-type multiple systems and 182 common multiple and double stars could be detected.Based on present-day observational data and the author's photographic observations, the kinematic of Trapezium-type multiple stars of spectral class 0-B2 is studied.
Some Aspects of the Evolutionary Status Of W Ursae Majoris Binaries Deduced from Observational Data
Authors: Van Hamme Walter 
Published: July 2016

AbstractWe have developed a test for the evolutionary state of W Ursae Majoris binaries by comparing the observed spectral type of 31 of these systems (14 of type W and 17 of type A) with the expected one
when their primary component is an unevolved main sequence star. It appears that both the W- and A-type systems have a primary with a mass and radius too large to be compatible with the observed spectral
type,so there is no indication that each type should mark a different evolutionary stage.
Mass Flow due to Heating in a Binary System: Application to U Cephei
Authors: Kondo Yoji , Modisette Jerry L. 
Published: July 2016

AbstractWe have investigated the possibility of mass flow due to the heating of the cooler component in a close binary system. The heating may be caused by irradiation from the hotter companion or by other mechanisms such as the spacial coincidence of non-linear “g-mode” oscillations in the cooler star. The 2.4-day period binary U Cep, in which gas streaming has been observed, has been chosen for model calculations. Preliminary results show that such a heating of the lower atmosphere of the cooler star could lead to mass flow at an average rate of 10-9 to 10-7 solar mass per year without the star's necessarily filling its critical Roche surface.
On a Possible Linkage between W-Type WUMa Systems and the Short Period RSCVn-Like Binaries
Authors: Milano L. , Russo G. , Mancuso S. 
Published: July 2016

AbstractWe analize the general properties of a group of WUMa-type binaries, which show RSCVn-like activity. The position of these stars in the colour-density and mass-orbital momentum diagrams is studied, but no definite answer can be given on the linkage between short period RSCVn systems (SPG) and WUMa systems with RSCVn-like activity (WWG).
Apparent thickness of Saturn’s rings from the observations of the ring plane crossing
Authors: Sicardy Bruno , Laques Pierre , Lecacheux Jean , Brahic André , Wlerick Gérard 
Published: July 2016

ABSTRACTThe reductions of electronographic plates taken during ground-based observations of Saturn at the times of the transits of the Sun and the Earth through the ring plane (March 1980) are interpreted.1. The variation of the ring’s brightness vs. elevation angle around Earth’s crossing is different from the variation around Sun’s crossing. Furthermore, the ring’s brightness increases with the distance to Saturn’s centre around Earth’s crossing and decreases around Sun’s crossing. This allows to derive the illumination of the Saturn’s disc on the rings and indicates that the rings do not behave like an homogeneous scattering layer when observed or lit almost edge-on.
The Saturn ring particles from optical reflectance polarimetry
Authors: Dollfus Audouin 
Published: July 2016

ABSTRACTThe light reflected by the Saturn rings is polarized; the degree and azimuth of the polarization varies with the phase angle, the wavelength and the position on the ring.For ring B, the polarization is the result of three combined effects which have been separated: – First, a polarization Poby the direct reflection of the sunlight on the ring particles; in the visible light, this polarization is compatible with the model of dirty-ice blocks, but in UV the scattering is dominated by a population of micron size particles. – Second, a polarization by the light which is reflected by the rings from the Saturn globe. – Third, a component with an azimuth always radial from the disk center and which varies with time, often significantly in a few days, in ways which are not predictable. An organized structure in or between the blocks making the rings is needed and suggested explanations are discussed.For Saturn ring A, the component of polarization produced by direct reflection suggests ring particles of the same type as for the blocks in ring B. But, in addition, very variable polarizations are observed, with azimuths often tilted locally for several tens of degrees from the scattering plane; clear relationships are not yet identified.
Voyager UVS observations of stellar occultations by the rings of Saturn
Authors: Holbelg J.B. , Forrester W.T. 
Published: July 2016

ABSTRACTDuring the Voyager 1 and 2 Saturn encounters the ultraviolet spectrometers observed three separate stellar occultations by Saturn's rings. Together these three observations, which sampled the optical depth of the rings at resolutions from 3 to 6 km. can be used to establish a highly accurate distance scale allowing the identification of numerous ring features associated with resonances due to exterior satellites. Three separate observations of an eccentric ringlet near the location of the Titan apsidal resonance are discussed along with other ringlet-resonance associations occurring in the C ring. Density waves occurring in the A and B rings are reviewed and a detailed discussion of the analysis of one of these features is presented.
Perturbed particle disks
Authors: Borderies N. , Goldreich P. , Tremaine S. 
Published: July 2016

ABSTRACTWe solve the Boltzmann moment equations to determine the disk particle velocity ellipsoid near an isolated satellite resonance. In a coordinate frame which rotates with the pattern speed of the perturbation potential the solutions are stationary functions of the azimuthal angle. From the velocity ellipsoid we obtain the stress tensor due to particle collisions and consequently, the viscous angular momentum flux. We find that in sufficiently perturbed regions there are ranges of azimuthal angle within which the radial component of the angular momentum flux is negative. It is even possible for the angular momentum luminosity, the radial flux integrated over azimuth, to be negative. We also show that the magnitude of the rate of deformation tensor in a perturbed particle disk is bounded from above by Ω(1 + τ2)½, where Ω is the orbital angular velocity and τ Is the optical depth. These results are applied to sharp edges of planetary rings, the decay of density waves, and the damping of differential precession and eccentricity in narrow ringlets.
Size distribution in collisional systems distribution de tailles dans les systemes collisionnels
Authors: Clairemidi S. 
Published: July 2016

ABSTRACTThe dynamical evolution of a three dimensional system of particles of different masses and sizes, orbiting in the gravitational field of a central body, and interacting through inelastic collisions is studied here. Recent fly-bys of planetary rings and observations of flat galaxies with modern receptors indicate that a number of structures discovered in collisional systems can be understood only of three ingredients are included in the models, namely interparticles collisions , distributions of particles sizes and self attraction of the particles.