bluuebunny/crossref_metadata_2025_split huggingface dataset:
A Model of the Soft X-Ray Background as a Blast wave Viewed from Inside
Authors: Edgar Richard J. , Cox Donald P. 
Published: July 2016

AbstractThe suggestion that the soft x-ray background arises In part from the Sun being inside a large (R ∼ 100 pc) supernova blastwave is examined by producing models of spherical blastwaves. Such models can produce quantitative fits to both surface brightnesses and energy band ratios (for the lowest energy bands) when t ∼ 105 yr, EO = 5 x 1050 ergs, and nO ≃ 0.004 cm-3.Such models can be generalized by varying the relative importance of such factors as thermal conduction, Coulomb heating of electrons, and external pressure; by allowing the explosions to occur In pre-existing cavities with steep density gradients, or by examining the effects of large obstructions or other anlsotroples in the ambient medium.
Radial-Velocity Work at Cambridge and Palomar
Authors: Griffin R.F. 
Published: July 2016

The Cambridge radial-velocity spectrometer must be the oldest instrument to qualify as relevant to the main theme of this meeting. It was the first instrument to measure radial velocities photoelectrically, and has been the principal source of observational data for more than 100 published papers. Nearly 19 years after it was brought into operation it is still in active use — indeed, I have been observing with it this very week.The principal observing program is concerned with spectroscopie binaries, and at any given time has about 200 objects on it. Although the weather in Cambridge is poor, the 36-inch telescope has been almost continuously available for radial-velocity work for the last ten years. On the whole, there is as much observing time available as I can use, and its distribution in time is much more favourable for work on spectroscopie binaries than the typical distribution of nights allocated to any one observer on a more popular telescope. Among the orbits written up recently, noteworthy examples are those of HD 210647 (the most eccentric spectroscopie orbit, with e = 0. 904), HR 1105 (the first for an S-type star) and 6 Boo (whose amplitude of little more than 1 km/s is smaller by a factor of two than that of any other orbit that I consider to be reasonably secure).
A Search for Constant Velocity B and A Stars
Authors: Fekel Francis C. 
Published: July 2016

AbstractOver the past few years high dispersion spectroscopie observations have been obtained for a number of close visual binaries and multiple stars. Because velocity variations in such binaries are relatively small, just a few 10’s of km s−1 at most, and because of the long timespan of the observations, a few years to several decades, the velocities must be very accurate and systematic effects kept to a minimum. This is particularly true since observations have been obtained at several different observatories with several different spectrograph-detector systems. With the advent of solid-state Reticon and CCD detector systems data reduction has primarily been done by cross-correlating the spectrum of a program star with the spectrum of a constant velocity star of similar spectral type. As a result a search for constant velocity stars of B and A spectral type was begun recently. Included in the survey are 6 early B stars, 8 late B stars and 15 early A stars. All have v sin i ≤ 55 km s−1 and about two-thirds have v sin i ≤ 25 km s−1.
Measures of RR Lyrae Stars
Authors: Burki G. , Meylan G. , Mayor M. 
Published: July 2016

Four RR Lyrae stars have been measured in Oct.-Nov. 1983 from the Observatoire de Haute Provence in France (radial velocities with CORAVEL) and from La Silla Observatory in Chile (Geneva 7-color photometry). General information on these stars is listed in the following table. The quantities N and σ are the number of measurements and the typical precision of one measurement.The variation of the radial velocity with the pulsation cycle of each star is shown in Fig. 1. Especially noteworthy is the very quick decrease of the radial velocity in the cases of RR Cet and DX Del.
G117-B15A: How is it Evolving?
Authors: Kepler S.O. , Vauclair G. , Nather R.E. , Winget D.E. , Robinson E.L. 
Published: July 2016

AbstractThe measurement of the rate of change of period with time for the g-mode pulsations in ZZ Ceti stars is a direct measurement of the cooling timescale for a DA white dwarf, which in turn can give a totally independent measurement of the age of the galactic disk. Using asteroseismology, we have obtained a rate of change of the period of the dominant pulsation in the light curve of the ZZ Ceti star G117-B15A of dP/dt = (12.5 ± 5.5) × 10−15s/s, equivalent to a timescale for period change of P/P = (5.5 ± 2.4) × 108 yr, which is consistent with the theoretical value for the cooling timescale of a DA white dwarf around 11,000 K.
Thomson Scattering in Magnetic Fields
Authors: Whitney Barbara 
Published: July 2016

AbstractThe equation of transfer in Thomson scattering atmospheres with magnetic fields is solved using Monte Carlo methods. Two cases, a plane parallel atmosphere with a magnetic field perpendicular to the atmosphere, and a dipole star, are investigated. The wavelength dependence of polarization from a plane-parallel atmosphere is qualitatively similar to that observed in the magnetic white dwarf Grw+70°8247, and the field strength determined by the calculation, 3.2×l08 G, is quantitatively similar to that determined from the line spectrum. The dipole model does not resemble the data as well as the single plane-parallel atmosphere.
Statistical Properties of Algol-Type Systems
Authors: Giuricin G. , Mardirossian F. , Mezzetti M. 
Published: July 2016

AbstractWe have inspected the observational data of 114 Algol-type binaries in order to clarify some general aspects of their evolutionary scenario. Through a comparison with the corresponding available statistical analyses of large sample of eclipsing and spectroscopic binaries, we have found a larger than normal concentration of low values of masses, binary separations and specific orbital angular momenta for Algol-type stars. Furthemore, high mass ratios predominate in massive and early-type Algol systems, whereas high total masses are generally accompanied by less prominent oversized and overluminous properties of the mass-losing components.
On the Possible Short-Period Irregular Light Fluctuations of V1357 CYG =CYG X-1
Authors: Kumsiashvili M.I. , Kraicheva Z. 
Published: July 2016

AbstractPhotoelectric observations in U, B, V, were carried out to study the possible rapid (during a night) fluctuations of the close binary system V1357 Cyg, including the X-ray source Cyg X-1. Assuming the existence of irregular fast light fluctuations in the X-ray source Cyg X-1,the conclusion can be drawn that during these observations in 1979 the amplitude of the variations did not exceed 0.04 mag.
Comments on collision mechanics in ring systems
Authors: Hartmann William K. 
Published: July 2016

ABSTRACTThe nature of collisions within ring systems is reviewed with emphasis on Saturn's rings. The particles may have coherent icy cores and less coherent granular or frosty surface layers, consistent with thermal eclipse observations. Present-day collisions of such ring particles do not cause catastrophic fragmentation of the particles, although some minor surface erosion and reaccretion is possible. Evolution by collisional fragmentation is thus not as important as in the asteroid belt.
Multivalued electrostatic potentials; “ chance or necessity ” for the charge of solid particles near Saturn?
Authors: Meyer-Vernet N. 
Published: July 2016

ABSTRACT:In a plasma with (cold) electrons temperature between typically 10 eV and several KeV, the secondary emission on solid particles plays an important role. In particular, in the presence of suprathermal electrons, the potential can have two stable equilibrium states in a given environment: then, the sign of the charge depends on minor historical accidents of the system, and small environmental perturbations yield important jumps of charge. To illustrate this point, well-known by space-craft charging specialists, we investigate the charge's response to a slight variation of ambient parameters near Saturn (flux of suprathermal electrons ; passage from shadow to sunlit). The results are often opposite to those given by either usual “rules of thumb”, or uncareful numerical calculations. The importance of the process is evaluated for different saturnian environments. Some possible consequences for grains physics (dynamics in electromagnetic fields, agglutination and disruption) are discussed.
The asteroid ring
Authors: Dermott S.F. , Murray C.D. 
Published: July 2016

ABSTRACTThe asteroid belt between Mars and Jupiter has some features in common with planetary rings; these include gaps associated with resonances and a tendency for pericenter alignment. While it is tempting to think of the Jupiter-asteroid belt system in terms of satellite-disk interactions, the present low spatial density of the belt limits, for example, the application of the spiral density wave theory, which has achieved some success in explaining the resonant structure of Saturn's rings. However, some authors claim that this process, and some other processes, would have been effective in the belt's early history, if the belt was then both flatter and more massive. It is likely that Jupiter's orbital period was then at least slightly different from the present period. From a statistical analysis of the asteroid orbital period data, we show that the present distribution of asteroids is strongly correlated with the present orbital period of Jupiter (to 1 part in 5000). Furthermore, by analyzing the distribution of orbital eccentricities and inclinations we show that the resonant structure of the belt was formed after the asteroids had dispersed from the near-coplanar disk in which they accreted.
Non-Equilibrium Ionisation in Supernova Remnants - A Case Like Tycho - A case like Tycho
Authors: Brinkmann W. , Fink H.H. 
Published: July 2016

AbstractX-ray observations of young supernova remnants (SNR) provide the most direct tool to study their evolution, their chemical composition, and their interaction with the interstellar medium. We will show for a SNR with the characteristics of Tycho that great care has to be taken in interpreting spectral data obtained with X-ray detectors with low spatial resolution.
The X-ray Emission from SN 1987A and the Remnant of SN 1572 (Tycho)
Authors: Itoh Hiroshi , Masai Kuniaki , Nomoto Ken’ichi 
Published: July 2016

AbstractThe thermal X-ray emission from SN 1987A may be enhanced to a detectable level when the blast shock hits the circumstellar medium which has formed in the red-supergiant stage of the progenitor.The X-ray spectrum of Tycho observed with the satellite Tenma can be explained approximately within the context of a carbon deflagration model for Type la supernovae, if the ejecta are assumed to be mixed partially.
Gravitational and Dynamical Instabilities of a Decelerating Plane-Parallel Slab of Finite Thickness
Authors: Voit G. Mark 
Published: July 2016

AbstractIn order to explore how supernova blast waves might catalyze star formation, we investigate the stability of a slab of decelerating gas of finite thickness. We examine the early work in the field by Elmegreen and Lada and Elmegreen and Elmegreen and demonstrate that it is flawed. Contrary to their claims, blast waves can indeed accelerate the rate of
star formation in the interstellar medium. Also, we demonstrate that in an incompressible fluid, the symmetric and antisymmetric modes in the case of zero acceleration transform continuously into Rayleigh-Taylor and gravity-wave modes as acceleration grows more important.
Atmospheric Shocks in Mira Variables – MgII Emission
Authors: Brugel Edward W. , Beach T.E. , Willson L.A. , Bowen G.H. 
Published: July 2016

AbstractWe have undertaken an extensive program to investigate atmospheric shock dynamics in Mira variables through monitoring the MgII emission strengths versus phase. Theoretical calculations of Bowen (1987), which represent the structural variations in the extended atmosphere of a pulsating Mira, are presented in addition to the MgII observations. The model calculations generate density, temperature and velocity structures as determined by stellar parameters and by interactions of the driving amplitude, dust opacity and thermal relaxation processes. The main diagnostic provided by the models is the total emitted shock luminosity versus phase, which can be compared to the observed MgII emission. Models and observations are presented for three Miras: S Car, R Car and T Cep.
Thermonuclear Runaways on Accreting Hot White Dwarfs
Authors: Prialnik Dina , Regev Oded 
Published: July 2016

AbstractPreliminary results of 1–D fully hydrodynamic numerical calculations including accretion and mass loss on a 1M⊙ hot white dwarf are presented. For the case of Ṁ = 10−8M⊙/yr and Teff = 125000°K we get flashes of duration of ∼ 30 – 40 yrs which reccur every ∼ 1500 years. During each flash ∼ 6x10−6M⊙ is lost (∼ 40% of the accreted envelope.
The Observations of AG PEG During 1985–87
Authors: Boyarchuk A.A. , Belyakina T.S. , Tarasov A.E. , Tomov N. 
Published: July 2016

AbstractThe light curves in UBVRI and profiles of the emission lines of Hα, HeII 5411 and HeI 5876, 6678 obtained during 1985–87. The radial velocities of the emission lines HeI 6678 and HeII 5411 demonstrated clear periodic variations in antiphase with the radial velocity defined for the absorption line.
Criteria and Applications of the MK Classification System
Authors: Garrison R. F. 
Published: July 2016

AbstractA review is given of the present state of MK classification, with a view to future developments in techniques and instrumentation. The principle of the complementarity of quantitative and visual inspection techniques is stressed.Included in the discussion are examples of problems which are currently outstanding. Among these are variable stars, marginal peculiarities, fundamental standards (with specific reference to the Sun), and representation of the third and higher dimensions.
Some Lessons from the Past and Thoughts on the Future of Spectral Classification
Authors: Walborn N. R. 
Published: July 2016

AbstractThe importance of maintaining the greatest possible independence of spectral classification from theoretical or other external information is emphasized anew, with reference to some historical discussions now seen with the benefit of hindsight. This ideal requirement applies equally to the development and to the application of a classification system, although in practice some well-established information may guide one’s intuition in the initial hypothetical formulation. The fundamental position of this principle in the MK approach to classification is a major reason for the value of its spectral types, and for its continuing success in uncovering new phenomena. The ability of a particular technique to produce interesting or useful results is surely the most significant criterion of its value, and from this viewpoint it appears that new techniques and methods will complement rather than replace traditional spectral classification. Finally, the unique importance at this time of applying both new and traditional methods to spectral classification in the Magellanic Clouds is stressed; they provide the only current opportunity for detailed spectroscopic examination of numerous stars in external systems. It is essential that large telescopes be utilized for this work so that the best attainable observational quality may be maintained, and the many fascinating phenomena revealed by spectral classification in the Galaxy can be comparatively investigated to the maximum extent praticable in the Magellanic Clouds
Extraterrestrial Molecules: Present and Future Observations from Space
Authors: Cosmovici Cristiano Batalli 
Published: July 2016

AbstractIn the last ten years Molecular Astrophysics has become an extremely interesting field of interdisciplinary research as a result of unexpected discoveries of complex organic molecules made by radioastronomy in many regions and objects of the Galaxy. Since not all molecules have detectable transitions through the atmospheric windows, the development of UV and IR space astronomy will allow us to study new important molecular transitions in the interstellar medium and in the atmospheres of cool stars and comets. In this paper the present status of molecular astrophysics will be described and special emphasis will be devoted to the importance of IR space astronomy for the future knowledge of molecular species in the interstellar medium and in the atmospheres of Carbon stars where the low temperatures are particularly, suitable for infrared studies
Classification Spectrale Dans Le Futur
Authors: Fehrenbach Ch. 
Published: July 2016

Ce Colloque, organisé en l’honneur du Centenaire du Père Secchi, arrive a un bon moment pour faire le point sur le passe: les classifications de Secchi, de Harvard, le systeme Morgan et Keenan et examiner les problèmes d’avenir.D’abord, quel est le but des classifications? Certains théoriciens ont l’impression que nous sommes dans la même position qu’un zoologiste classant des animaux. Mais cette impression est fausse: d’abord les animaux existent en espèces discontinues alors que les spectres stellaires forment un continuum.
Simultaneous Five Color (Ubvri) Polarimetry of EF Eri
Authors: Piirola V. , Reiz A. , Coyne G.V. 
Published: July 2016

AbstractWe present the first observations of the AM Her type object EF Eri where both the polarization and the photometric data are recorded simultaneously in five color bands (UBVRI). The position angle rotates strongly (~30° ) vs. wavelength from U to 1, probably due to Faraday rotation or due to fact that the polarized radiation seen in the different wavelength bands comes from different parts of the accretion region. The phase dependence of the position angle requires field and accretion geometry more complicated than a simple centered dipole and a second emitting region producing weaker intermediate pulses in the infrared seems to be present. We derive the value of the inclination of the system i = 55° ± 5° , the colatitude of the active pole βl = 38° ± 5° i and the second emitting region β2 = 115° ± 5° , both of which are nearly at the same longitude facing the main accretion stream.
EUV and FUV Observations of Cataclysmic Variables
Authors: Polidan R.S. , Carone T.E. 
Published: July 2016

AbstractIn this paper we present recent results from a continuing investigation of cataclysmic variables in the 500 to 1700 A region with the Voyager ultraviolet spectrometers. Observations of outbursts show a substantial delay (~0.5 day) in the rise to maximum in the FUV (912–1200 Å) with respect to optical wavelengths. Both FUV and optical light decline simultaneously. Flux distributions show a significant flattening in the FUV and with the possible exception of CPD-48 1577 no EUV flux has been observed in any catalclysmic variable. CPD-48 1577 shows a marginal, 2 σ EUV flux.
A Review of the Classical Nova Outburst
Authors: Starrfield S. , Sparks W.M. 
Published: July 2016

AbstractWe review the recent observational and theoretical studies of the nova outburst. The observational studies have not only identified a new class of novae but theoretical simulations of this class have been found to be in excellent agreement with the observations. This new class consists of outbursts occurring on ONeMg white dwarfs in close binary systems in contrast to the other outbursts which are occurring on CO white dwarfs. We also review the effects of the β -unstable nuclei and show how their presence has a major effect on the evolution.
A Survey of Nova Remnants
Authors: Duerbeck H.W. , Seitter W.C. 
Published: July 2016

AbstractExnovae and nova shells are generally faint and difficult to observe. Only a few have been studied, and even less of them in sufficient detail. We give a progress report on our survey of exnovae and nova shells, especially on the results of a spectral survey of novae in the southern Milky Way. The three-dimensional structure in the light of Hα derived for the nebula of GK Per is displayed.
Properties of the Emission Regions in AM Her Stars
Authors: Beuermann K. 
Published: July 2016

AbstractThe emission regions on the white-dwarf primaries of AM Her type systems are suggested to be extended and offset from the magnetic pole similar to the oval arc of emission formed by the Earth’s auroral zone. In ST LMi and EF Eri, the emitting areas of the bremsstrahlung, the soft X-ray, and the cyclotron sources are shown to display a hierarchy with a small bremsstrahlung core being surrounded by a larger cyclotron halo. Core and halo are characterized by large differences in specific accretion rate with that in the bremsstrahlung core corresponding to a sizable fraction (≳10%) of the Eddington rate.
Accretion-Induced Collapse of Old White Dwarfs
Authors: Isern J. , Canal R. , Hernanz M. , Labay J. 
Published: July 2016

AbstractThere is observational evidence of the presence of young neutron stars in old binary systems. A likely explanation is that those neutron stars were produced in the collapse of old CO white dwarfs. We show how mass accretion on initially solid white dwarfs can leave central solid cores when dynamical instability sets in and we study the different effects of the existence of such cores on the outcome of the competition between thermonuclear explosion and gravitational collapse.
EXOSAT Medium Energy Observations of CYG X-2 Spectra and QPOs
Authors: Chiappetti L. , Ciapi A.L. , Maraschi L. , Stella L. , Tanzi E.G. , Treves A. 
Published: July 2016

AbstractHe report on a series of observations of Cyg X-2 obtained with EXOSAT in September 1983 at five phases in a single orbital cycle (P = 9.8 days, see Cowley et al. 1979). Here we present spectral data obtained with the Argon counters of the Medium. Energy experiment (HE) (see Turner et al. 1981), together with the search of Quasi Periodic Oscillations (QPOs) in high tine resolution data.
Optical Spectroscopy of CH Cygni in 1985/86
Authors: Mikolajewski M. , Tomov T. , Mikolajewska J. 
Published: July 2016

AbstractSome arguments for the explanation of the spectroscopic and photometric behavior of CH Cyg in terms of an eclipsing binary with P=5700 days, consisting of M6 III star and an accreting white dwarf, are presented. Physical and geometrical parameters of the system have been estimated and discussed.
Combined Satellite and Ground-Based Observations of the Quiescent, High Latitude Symbiotic Variable AG Draconis = BD+67°922
Authors: Slovak M.H. , Cassinelli J.P. , Anderson C.M. , Lambert D.L. 
Published: July 2016

AbstractSatellite observations, from Einstein, IUE, and IRAS, have been combined with ground-based observations to derive the quiescent energy distribution of the symbiotic star AG Draconis. A detailed comparison is made between the combined observations and various steady-state composite models, including blackbody accretion disks.
The Asterisms
Authors: Chakravarty A.K. 
Published: July 2016

A system of 27 asterisms, or nakṣatras, plays an important role in Indian astronomy and calendrical science. The present convention is that the ecliptic is divided into 27 equal parts each 13°20' long commencing from one initial point. These arcs are called nakṣatras. Again a bright or prominent star of each division is called yogatārā bearing the name of the are division e.g., Kṛttikā as nakṣatra means an are division and as a yogatārā it means the star η Tauri of the Pleiades group.The origin of this asterism system is very old. The names of these stars appearin Vedic litrature. The Taittirīya, Kāṭhaka, Maitrāyaṇī Saṃhitas and the 19th book of Atharva Veda, each has given a list of 27 nakṣatras (the last two have included an additional star, Abhijit (αLyrae), making a total of 28 nakṣatras). All these lists always begin with the name kṛttikas (the star group Pleiades), and order of names of stars are more or less the same. Some of the stars changed their names in different hands; but they are always either star groups or single stars, and never arc divisions.