bluuebunny/crossref_metadata_2025_split huggingface dataset:
The Hot Galactic Corona and the Soft X-ray Background
Authors: Daniel Wang Q. 
Published: July 2016

AbstractI characterize the global distribution of the ¾ keV band background with a simple model of the hot Galactic corona, plus an isotropic extragalactic background. The corona is assumed to be approximately polytropic (index = 5/3) and hydrostatic in the gravitational potential of the Galaxy. The model accounts for X-ray absorption, and is constrained iteratively with the ROSAT all-sky X-ray survey data. Regions where the data deviate significantly from the model represent predominantly the Galactic disk and individual nearby hot superbubbles. The global distribution of the background, outside these regions, is well characterized by the model; the 1σ relative dispersion of the data from the model is ~ 15%. The electron density and temperature of the corona near the Sun are ~ 1.1 × 10−3 cm−3 and ~ 1.7 × 106 K. The same model also explains well the 1.5 keV band background. The model prediction in the ¼ keV band, though largely uncertain, qualitatively shows large intensity and spectral variations of the corona contribution across the sky.
Diffuse Ionized Gas in Halos of Spiral Galaxies
Authors: Dettmar Ralf-Jürgen 
Published: July 2016

AbstractOver the last couple of years Diffuse Ionized Gas (DIG) has been identified as an important constituent of the interstellar medium (ISM) in the halos of spiral galaxies. Imaging in and spectroscopy of optical emission lines allow us to study the distribution and excitation of this gas with a spatial resolution not achievable for other phases of the ISM in external galaxies. Its origin and ionization is under debate and give important constraints for models of the ISM in general and on the large scale exchange of matter between disk and halo in particular. This review summarizes more recent observational results and compares them with model predictions. The data available now demonstrate that the presence of DIG in the disk-halo interface of spiral galaxies is related to star formation processes in the underlying disk. While photoionization by OB stars in the disk seems a viable source for the power required to ionize the DIG, additional processes are needed to explain some of the spectral features. The observed correlation with properties of the non-thermal radio continuum indicate that magnetic fields and cosmic rays could play a role for the physics of this medium.
Disks of Classical Be Stars
Authors: Štefl Stanislav 
Published: July 2016

AbstractObservational methods used in investigation of circumstellar disks of Be stars significantly changed during the last decade. While mostly the studies of line profiles in the optical and near-IR region were used in the 70th and 80th, the present progress is done also thanks to interferometric and polarimetric observations. These techniques enable to determine the geometrical parameters of the circumstellar disks directly for the first time. They are flattened and axially symmetric. Their H α emission region extends typically up to several tens of stellar radii. Systematic long-term spectroscopic monitoring helped to define and partly interpret the line-profile variability of emission lines on different time-scales. Variations on a time-scale of hours may appear after the matter is ejected during the outburst. The V/R variations with periods of the order of 10 years reflect the global disk oscillations.
Polarimetric Evidence of Non-spherical Winds
Authors: Magalhães Antônio Mário , Rodrigues Cláudia V. 
Published: July 2016

AbstractPolarization observations yield otherwise unobtainable information about the geometrical structure of unresolved objects. In this talk we review the evidences for non-spherically symmetric structures around Luminous Hot Stars from polarimetry and what we can learn with this technique. Polarimetry has added a new dimension to the study of the envelopes of Luminous Blue Variables, Wolf-Rayet stars and B[e] stars, all of which are discussed in some detail.
Physics of Radiatively Driven Winds by High Angular Resolution Observations (HARO)
Authors: Stee Ph. , Bonneau D. , Mourard D. , Vakili F. 
Published: July 2016

AbstractNumerous models have been developed during the last two decades which try to fit a small number of “classical” observables as closely as possible (i.e Hα line profile and continuum energy distribution or polarization data). Nevertheless, little has been done to include High Angular Resolution Observations (HARO) in simulations in spite of the fact that such data can strongly constrain radiative wind models. In the following, we shall review recent results coming from HARO of active B stars and we shall focus on our radiative wind model for active hot stars which integrates these measurements.
UV Wind Variability in B Supergiants and its Implications for Wind Structures
Authors: Massa Derek , Prinja Raman K. 
Published: July 2016

AbstractWe discuss why B supergiant winds are particularly well suited for wind studies, and present or refer to dynamic spectra which suggest the presence of disks, bifurcated winds, shock formation, rotationally modulated winds and the spontaneous generation of wind enhancements. They underscore the strength and richness of wind variability in B supergiants and the challenges these phenomena present to theoretical studies of stellar winds.
The Long-Term Variability of Luminous Blue Variables
Authors: Humphreys Roberta M. 
Published: July 2016

AbstractThe stars known as Luminous Blue Variables include two very distinctive subgroups - the S Dor-type variables which basically define what we call an LBV and the much rarer ‘giant eruption’ LBV’s which include famous stars like η Car and P Cyg. The distinctive characteristics and long term variability of these two groups is reviewed. The lesser 1890 eruption of η Car is shown to have been much more significant than previously believed and resembles the second peak seen in the historic light curve of P Cyg. Because so many, if not all, stars in certain parts of the HR diagram appear to be luminous, blue, and variable, I suggest returning to our previous designation - S Dor variables and η Car variables for these two important groups of stars.
Pulsations in O Stars
Authors: Henrichs Hubertus F. 
Published: July 2016

AbstractO stars are located in a domain of the HRD where nonradial pulsations are expected. Photometric surveys did not reveal pulsating O stars, showing that the amplitudes must be very small. Intensive spectroscopic studies yielded pulsation modes for very few O stars only, although many are line-profile variables. Wind contamination of many spectral lines is a major difficulty. Future concentrated spectroscopic efforts will undoubtedly increase the number of pulsating O stars.The current status of our knowledge of pulsations in these stars is reviewed. From one specific example a critical attitude emerges towards the quantitative results reached so far. We also address the question whether non-radial pulsation can be the cause of the non-spherical time-dependent winds of these stars.
Ring Nebulae Abundances: Probes of the Evolutionary History of Luminous Blue Variable Stars
Authors: Smith Linda J. , Nota Antonella , Pasquali Anna , Leitherer Claus , Clampin Mark , Crowther Paul A. 
Published: July 2016

The ring nebulae that surround most Luminous Blue Variable (LBV) stars are believed to be the relics of one or more giant eruptions (cf. Nota, these proc.). The nebulae thus represent the stellar surface layers at the time of the eruption(s) and by analysing their chemical composition and dynamics, it is possible to infer the past evolutionary state of the star.Observations with the Hubble Space Telescope (HST) and the Faint Object Spectrograph (FOS) were obtained for the nebulae around the two LMC LBVs R127 and R143, and the Ofpe/WN9 star S119 for the purpose of obtaining abundances. The spectra cover the wavelength range 3235–6818 Å and aslit of dimensions 1″.7 × 0″.2 was placed on the brightest portion of each nebula. Full details of these observations are given in Smith et al. (1998).
On Stable Chaos in The Asteroid Belt
Authors: Šidlichovský Miloš 
Published: July 2016

AbstractThe twenty most chaotic objects found among first hundred of numbered asteroids are studied. Lyapunov time calculated with and without inner planets indicates that for eleven of those asteroids the strongest chaotic effect results from the resonances with Mars. The filtered semimajor axis displays an abrupt variation only when a close approach to Mars takes place. The study of the behaviour of the critical argument for candidate resonances can reveal which is responsible for the semimajor axis variation. We have determined these resonances for the asteroids in question. For the asteroids chaotic even without the inner planets we have determined the most important resonances with Jupiter, or three-body resonances.
Migration of Trans-Neptunian Objects to The Earth
Authors: Ipatov Sergei I. 
Published: July 2016

AbstractMigration of trans–Neptunian objects under their mutual gravitation influence and the influence of the giant planets is investigated. These investigations are based on computer simulation results and on some formulas. We estimated that about 20 % of near–Earth objects with diameter d ≥ 1 km may have come from the Edgeworth–Kuiper belt.
A Global Analysis of The Generalized Sitnikov Problem
Authors: Chesley Steven R. 
Published: July 2016

AbstractThe isosceles three-body problem with Sitnikov-type symmetry has been reduced to a two-dimensional area-preserving Poincaré map depending on two parameters: the mass ratio, and the total angular momentum. The entire parameter space is explored, contrasting new results with ones obtained previously in the planar (zero angular momentum) case. The region of allowable motion is divided into subregions according to a symbolic dynamics representation. This enables a geometric description of the system based on the intersection of the images of the subregions with the preimages. The paper also describes the regions of allowable motion and bounded motion, and discusses the stability of the dominant periodic orbit.
Complements to Moons’ Lunar Libration Theory
Authors: Chapront J. , Chapront-Touzé M. , Francou G. 
Published: July 2016

AbstractAnalytical complements have been brought to Moons’ lunar libration theory concerning tidal effects, direct perturbations due to the Earth’s figure, and indirect non periodic perturbations. Comparisons to JPL numerical integrations DE245 and DE403 have been performed and the residuals treated by frequency analysis, allowing the determination of fitted free libration parameters and numerical complements.
Proper Elements and Stability of The Trojan Asteroids
Authors: Burger Ch. , Pilat-Lohinger E. , Dvorak R. , Christaki A. 
Published: July 2016

Up to now ~ 400 asteroids are known which move close to the Lagrangian equilibrium points L4 (246) and L5 (167) of Jupiter. In this investigation the orbits of all known Trojans were integrated numerically for 10 million years using the Lie Series integrator with adaptive stepsize (Hanslmeier and Dvorak, 1984) in the dynamical model of the outer planetary system. The goal of the study was to extend the computation of the proper elements for all known Trojans for a longer time interval; the respective results are compared to already existing ones (e.g. Bien & Schubart, 1987; Milani, 1993).The determination of the characteristic quantities proper eccentricity ep, proper inclination ip and libration D was done by numerical filtering techniques using the method of Labrouste (Burger, 1998) and by a very precise frequency analysis (Chapront, 1997). Our results differ from the ones calculated for a shorter time interval by Milani (1993) between 5% and 10%. In Fig.1 we plotted the nomogram for the three proper elements mentioned above for L4 and the ep for L5. As a new interesting result we found Trojans with 0.15 < ep < 0.22 for L4 (upper left) and L5 (upper right) which answers an open question of an existing gap in this range of the ep. For L4 Trojans there is a well defined maximum in the nomogram for ep ∼ 0.06; for the L5 Trojans the maximum is flat and shifted versus ep ∼ 0.07. The proper elements sin(ip) for L4 (bottom left graph) show a maximum for Trojans moving in the plane of Jupiter’s orbit and a decrease versus larger inclinations, although a plateau for 14° < i < 27° is visible; this confirms that the Trojan orbits are more inclined that the orbits of the main belt asteroids.
Orbits in a Stäckel Approximation
Authors: De Bruyne V. , Leeuwin F. , Dejonghe H. 
Published: July 2016

Because of their analytical simplicity and regularity, Stäckel potentials are attractive tools for modelling galaxies. The third integral I3 is explicitly known in a Stäckel potential, and can be used as an approximation to the effective third integral, in order to construct three-integral models (cf. Dejonghe, et al., 1996, A&A 306, 363).Moreover, Stäckel potentials turn out to yield good global descriptions for either axisymmetric or triaxial systems without central mass concentration (de Zeeuw 1985, MNRAS 216, 273, de Zeeuw & Lynden-Bell 1985, MNRAS 215, 713), and even for some systems with a black hole included (Sridhar & Touma 1997, MNRAS 292, 657).One long-standing concern though, is that Stäckel potentials form only a very small subspace in the family of all potentials. The main orbit families found by numerical integration in general triaxial potentials are present in a Stäckel potential (Schwarzschild 1981, ApJ 232, 236, de Zeeuw 1985, MNRAS 216, 273), but there is obviously no place in an integrable potential for smaller orbital families or stochastic orbits. However, since regular orbits are the rule rather than the exception, a potential which yields a good representation of those orbits is certainly a good basis for building models.
Dynamics of the Mimas-Tethys System
Authors: Champenois Sylvain 
Published: July 2016

AbstractThe role of the 200 yr-long period found recently in the mean longitude of Mimas (Vienne and Duriez 1992) is investigated through numerical integrations. It is shown that it has a deciding effect on the descriptions of the resonance motion of the Mimas-Tethys system, as considered up to now. As a result, Mimas’s inclination before capture may have been higher (up to 0.7°) or lower (down to 0.03°) than the value previously considered (0.42°). Also, Tethys’s eccentricity on capture may have been quite higher (≈ 0.008 versus 0). Moreover, the probability of capture is found to be very sensitive to Tethys’s eccentricity, and possibly much higher (up to 1) than the value considered before (0.04).
Two Conjectures of G.D. Birkhoff
Authors: Mccord Christopher K. , Meyer Kenneth R. 
Published: July 2016

The spatial (planar) three-body problem admits the ten (six) integrals of energy, center of mass, linear momentum and angular momentum. Fixing these integrals defines an eight (six) dimensional algebraic set called the integral manifold, 𝔐(c, h) (m(c, h)), which depends on the energy level h and the magnitude c of the angular momentum vector. The seven (five) dimensional reduced integral manifold, 𝔐R(c, h) (mR(c, h)), is the quotient space 𝔐(c, h)/SO2 (m(c, h)/SO2) where the SO2 action is rotation about the angular momentum vector. We want to determine how the geometry or topology of these sets depends on c and h. It turns out that there is one bifurcation parameter, ν = −c2h, and nme (six) special values of this parameter, νi, i = 1, …, 9.At each of the special values the geometric restrictions imposed by the integrals change, but one of these values, ν5, does not give rise to a change in the topology of the integral manifolds 𝔐(c, h) and 𝔐R(c, h). The other eight special values give rise to nine different topologically distinct cases. We give a complete description of the geometry of these sets along with their homology. These results confirm some conjectures and refutes several others.
Nekhoroshev-Stability ofL4andL5in the Spatial Restricted Problem
Authors: Benettin Giancarlo , Fassò Francesco , Guzzo Massimiliano 
Published: July 2016

The Lagrangian equilateral pointsL4andL5of the restricted circular three-body problem are elliptic for all values of the reduced massμbelow Routh’s critical massμR≈ .0385. In the spatial case, because of the possibility of Arnold diffusion, KAM theory does not provide Lyapunov-stability. Nevertheless, one can consider the so-called ‘Nekhoroshev-stability’: denoting byda convenient distance from the equilibrium point, one asks whetherfor any small єe > 0, with positiveaandb. Until recently this problem, as more generally the problem of Nekhoroshev-stability of elliptic equilibria of Hamiltonian systems, was studied only under some arithmetic conditions on the frequencies, and thus onμ(see e.g .Giorgilli, 1989). Our aim was instead considering all values ofμup toμR. As a matter of fact, Nekhoroshev-stability of elliptic equilibria, without any arithmetic assumption on the frequencies, was proved recently under the hypothesis that the fourth order Birkhoff normal form of the Hamiltonian exists and satisfies a ‘quasi-convexity’ assumption (Fassòet al, 1998; Guzzoet al, 1998; Niedermann, 1998).
Chaos in Three-Body Dynamics: Intermittency, Strange Attractor, Kolmogorov-Sinai Entropy
Authors: Chernin Arthur D. 
Published: July 2016

The temporal structure of chaos in three-body dynamics is analyzed; the emphasis is made on a similarity and difference between three-body chaos and basic patterns of chaotic behaviour known in nonlinear physics.1. With the use of homology mapping (Agekian and Anosova 1967), we study a set of computer models of thee-body systems in a stationary spherically symmetric potential well (Valtonen et al. (1994); the well confines the bodies, and because of this the system can generate fairly long time series. Typical time series reveal sequences of seemingly periodic motion and short bursts of strong chaos that appear in an irregular manner (Heinämäki et al. 1998). The quasi-ordered states are associated with hierarchical homology, and the quasi-period of the low-amplitude oscillations is very near the period of the temporary close binary in the system. The high-amplitude irregular states are mostly due to active three-body interplay when each of the bodies interacts with the two others with almost equal intensity. In the evolutionary history of most systems, these two extreme kinds of states alternate in an apparently random way producing together a non-stationary pattern of unpredictable behaviour.
The Evolutionary Significance of Recurrent Novae
Authors: Webbink Ronald F. 
Published: July 2016

Within the past few years, it has become increasingly apparent that common novae and dwarf novae must owe their origin to binary systems of much larger initial separation than they now have (Paczynski 1976; Ritter 1975, 1976; Webbink 1975). This was demanded by the realization that the white dwarfs in these binaries are generally quite massive (see for instance Warner 1973; Robinson 1976). At the same time, the earlier association of these binaries with W Ursae Majoris-type progenitors could no longer be supported (Webbink 1976b).It was clear even from the first suggestion of the long-period progenitor hypothesis that, although there certainly exist processes which drain mass and angular momentum from a binary efficiently enough to produce a short period cataclysmic variable (CV, for brevity), and to which a long period binary is in all likelihood extremely vulnerable, the details of this transformation present a theoretical problem of formidable difficulty. Nevertheless, some progress on this problem is now being made: a crude model of the early phases of mass exchange is discussed below, and models relevant to later phases have been computed by Meyer and Meyer-Hofmeister (1979; see also Taam et al. 1978).
About The Correlation between the Period and Dispersion of the Light Curve of Mira Type Variables
Authors: Garcia Jamie R. 
Published: July 2016

AbstractDuring the last years we have been involved in research on the periods of Long Period Mira type variables. We obtained periods using photoelectric and visual observations.In order to see that these results have a reasonable accuracy we have made an analysis comparing the photoelectric and visual observations.As a result of this analysis we found a relation between the dispersion of the light curves obtained from visual data and the periods: θv= f(P), where f is a linear function due to the systematic errors of observations.
Microprocessor Controlled Photometer to Observe Rapidly Changing Variable Stars
Authors: Freeth R.V. , Griffiths B. , Tan Z.C. 
Published: July 2016

Abstract.A multicolour photometer capable of resolving rapid light fluctuations in stellar light output has been designed and is under construction. The system is unique in that overall control of the data acquisition process is effected by a microprocessor unit and although designed for use with the Auckland Observatory’s 50 cm Zeiss telescope, it’s semi-portable stand alone nature will enable it to be used at other observing sites as well. Since the instrument is programmable the data collection parameters may be easily altered to accommodate changes in observing techniques and provision of an accurate local UTC clock facilitates the use of the system for other types of observations with more stringent timing requirements. An outline of the system specifications is given and possible observing programmes are mentioned.’
The Carlsberg Automatic Meridian Circle and the plans for Anglo-Danish collaboration
Authors: Olsen H. J. Fogh , Helmer L. 
Published: July 2016

AbstractThe Brorfelde meridian circle has been automated. This incorporates a telescope setting system, a new type of photoelectric slit micrometer, improved photoelectric circle reading system, met. data reading system with rain detector and photoelectric collimation micrometer all controlled by an HP 2100 minicomputer. The setting system can do the setting within 10 sees to an accuracy of ±2.”. The circle reading system with an accuracy of ±.”04 is more reliable than the original system. These systems have been tested and used for data collection for determination of diam. cor. This includes 1080 readings which are performed automatically in about 9 hours. The remaining equipment has been built and is being tested during the year 1978. After final tests it is planned to move the telescope to La Palma in collaboration with RGO and IAC. It is hoped to erect the instrument at La Palma at the end of 1980. At least 100 000 o bs. per year with an m. s.e. of.”20 are expected. In ten years time proper motions for at least 200 000 stars with an accuracy of .”014 will be available besides the fundamental work which will include observations of all traditional solar system objects and also day time observations.
Huit campagnes d’observations de Saturne a l’Astrolabe Danjon a San Fernando
Authors: Sanchez M. 
Published: July 2016

Abstract:This paper contains an analysis of Saturn observations with Danjon astrolabe at San Fernando. These observations were obtained during eight winter campaigns (1970-1978). Table 1 gives the mean values for each of the quantities Δα and Δδ (astrolabe - American Ephemeris) and the mean square errors. Figure 1 to 8 shows the results (right ascension and declination) and the corresponding smoothing curves. The accuracy of these curves is also given in table 1. The analysis of the values Δα and Δδ seem to show that there are differences, between the theoretical development of ephemeris and the observations, of periodical character.
A uniform system of designation of catalogues and surveys of star position
Authors: Teleki G. , Sevarlic B. 
Published: July 2016

Summary:Introduction of an uniform digital system of designations of catalogues and surveys (lists) of star positions is proposed. The designations should comprise: 16 information groups with a total of 50 digits for observational catalogues and 10 groups with a total of 36 digits for other catalogues (derived, fundamental) and surveys of star positions.