bluuebunny/crossref_metadata_2025 huggingface dataset:
2. A Comparison of the Composition of New and Evolved Comets
Authors: Donn B.
Published: July 2016

The intensity ratio of the continuum to the molecular emissions was estimated in the spectra of eight-five comets. These consisted of 34 new, 1/a (orig) < 100 x 10-6 AU-1, 31 more evolved with 102 < 1/a < 104, and 20 periodic comets, P < 103 years. In each age group the comets were divided into two distance intervals, the first observed at less than 1 AU from the sun and the second category observed at more than 1 AU. No significant difference among the patterns of relative intensity distribution among four age groups was found. No general evidence for a difference between pre- and post-perihelion observations was found although in a few cases a pronounced effect occurs. Four conclusions are drawn. (1) There is no readily apparent difference in continuum to emission intensity ratio between new and more evolved comets. (2) An intrinsic distribution of this characteristic does occur. (3) Periodic comets with weak continua derived from new comets with the same property. (4) No weakening of the continuum in general occurs following perihelion passage. The infrared evidence for Comet Encke suggests that the faintness of its continuum may be caused by a size distribution containing only particles larger than about 10 μm.
5. Ice Grains in Space
Authors: Smoluchowski R.
Published: July 2016

Certain astrophysically interesting properties of ice grains depend upon their crystallinity. Lower temperatures such as those in the outer layers of a dust cloud favor amorphous ice, the center of the cloud may favor crystalline ice. Amorphous grains have different binding energies than crystalline grains resulting in different evaporation rates and affecting the distance from the sun at which dust is released in cometary tails. They have also different sticking and accommodation coefficients which affect the formation of H2 and of other molecules on their surfaces. In contrast to crystalline grains, amorphous grains can be easily ionized by the stellar ultraviolet photons with important consequences for surface reactions, heating, etc.
7. Chemistry of the Inner Coma: A Progress Report
Authors: Huebner W. F.
Published: July 2016

The composition of the inner coma is modeled assuming that about 30 chemical species composed of H, C, and O undergo reactions. Ionization and dissociation by solar radiation and over 100 forward and reverse reactions between atoms, molecules, and ions are considered in the kinetics. Vaporization from a simple H20 - C02 nucleus provides the initial composition of the gas near the surface.
6. Thermomechanical Fracturing of Meteorites During Atmospheric Passage
Authors: Lang B.
Published: July 2016

Thermal attack is the basic process that dominates the atmospheric passage of a meteorite. The severity of heating by shocked air (with temperature ranging from 10,000° K to 25,000° K) depends upon pre-atmospheric velocity and angle of entry. It can produce eventually a destructive thermal stress pulse inside the body. While gross fragmentation at higher altitudes seems to have mainly a thermal origin, at lower altitudes the destruction (with occasionally its remarkable abundance of fragments) is likely to be attributed to the combined effect of high temperature and increased pressure. If it is assumed that these conditions control both the number and size distribution of fragments, then much can be learned of the comminution process by studying the fragment distribution in existing meteorite falls.
3. Asteroid Surface Materials from Reflectance Spectroscopy: A Review
Authors: Gaffey M. J. , McCord T. B.
Published: July 2016

The quality and quantity of asteroidal spectral reflectance data has increased rapidly in recent years. This data can be either (a) classified into spectral, polarization and/or albedo groups (e.g., ‘C’, ‘S’, etc.) which should tend to lump together grossly similar materials, or (b) interpreted utilizing laboratory and theoretical understanding of spectral features (e.g., absorption bands, continuum shape and slope) which are diagnostic of mineralogy or mineral chemistry. Mineral assemblages have been identified on asteroid surfaces which are comparable to most known meteorite types or which have undergone the types of processes (e.g., melting and differentiation) necessary to produce the meteoritic assemblages. The ordinary chondrites, which dominate the meteoritic flux reaching the Earth’s surface, are very rare or absent on Main Belt asteroids but appear common on the small asteroids which approach or cross the orbit of the Earth. The present interpretations of asteroidal spectra are not yet quantitative enough to permit the evaluation of specific asteroids as the sources bodies of particular meteorite specimens in terrestrial collections.
1. The Evolution of Asteroids as Meteorite Parent-Bodies
Authors: Chapman C. R.
Published: July 2016

The hypothesis that the asteroid belt is the source region for nearly all meteorite remains viable and there is no compelling reason to ascribe any meteorites to cometary origin. On the other hand, uncertainties about the true composition of the larger S type asteroids and difficulties in finding plausible main-belt source-bodies for the ordinary chondrites leave room open for further speculation on this question. The scenario for the evolution of asteroids, based on collisional models of two distinct populations of different physical properties, is being criticized and refined. It remains uncertain whether this approach will ultimately prove to be the correct interpretation of the collisional evolution of asteroids.
6. Mixing Process of the Lunar Surface Materials and their Cosmic-Ray Exposure Age
Authors: Iriyama J. , Honda M.
Published: July 2016

From the cosmic ray exposure age data, (time scale 107 - 108 years), of the lunar surface materials, we discuss the mixing process of the lunar surface layer caused by the meteoroid impact cratering. The gardening effect calculated using a crater formation rate slightly modified from the current population data is consistent with observed exposure ages of the lunar samples.
10. A Statistical Investigation of Asteroid Families: Preliminary Results
Authors: Carusi A. , Massaro E.
Published: July 2016

The correct identification of asteroid families is a prerequisite for understanding their nature, their orbital evolution and their physical origin. For this reason, a statistical investigation of asteroid families has been carried out, using a new clustering technique developed by A. I. Gavrishin. Proper elements for 2764 asteroids (1810 numbered and 954 Palomar-Leiden-Survey (PLS) asteroids) have been computed. Using these data, the Gavrishin method gives only ten significant classes. Five of them are coincident with the Hirayama families 1, 2, 3, 5, and the Flora group, that cannot be univocally subdivided. The PLS families are recognized. Furthermore many small-sized families reported by several authors lose their statistical relevance.
3. Limits to Energetic-Proton Irradiation of the Primeval Nebula as the Origin of Isotopic Anomalies
Authors: Clayton D. D.
Published: July 2016

Anomalies in meteorites due to extinct 22Na and 26Al have been interpreted as due to energetic-proton irradiation of the primeval nebula. I discuss quantitative limits that can be placed on this hypothesis. I describe other abundance effects that would have to coexist if this idea were correct and energetic constraints of an astrophysical type. The existing evidence is more easily explained by presolar carriers that are needed in any case for other anomalies.
2. Comets and the Cosmogony of the Solar System
Authors: Vsekhsvyatsky S. K.
Published: July 2016

The quantitative processes of eruptive development of planets into comets and other small bodies is studied from the Physical and Orbital evolution of these minor bodies. The escape of comets (and of their products of decay) into interstellar space has been of the order of 1030 to 1031 during the lifetime of the solar system. The mean density of the planets and of their large satellites, and their specific rotational energy, serve as independent checks of the amount of lost material. As far back as 1955 and 1962, the eruption theory has predicted the high volcanic activity on Venus and Mars and on some satellites, that was actually discovered by Mariner 10 and Venus 9-10. Interstellar molecules confirm that ejection of cometary gases is widespread in the Galaxy. Six new bright short-period comets discovered in 1975 provide direct evidence for comet formation in the system of Jupiter in its 1961-1969 period of high activity. Brought together, these facts prove that planetary bodies began their existence at stellar temperatures. They cooled down from the surface, forming crusts of rocky and icy materials, that have initiated a long period of eruptive evolution, characterized by numerous cataclysms with the ejection of tremendous amounts of gas and dust, separated by more quiescent phases, like the present state of the earth. Comets, asteroids, meteoritic and meteoric material bear witness for the explosive processes on planetary bodies.
4. The Gaseous Composition of the Solar Nebula Inferred from Data of Comets and Interstellar Molecules
Authors: Shimizu M.
Published: July 2016

The observations of comets and other primordial objects must be used to deduce the gaseous composition of the solar nebula just before its condensation. Preliminary steps in this direction are reported here.
6. CI Chondrites: Comparison and Contrast to Other Meteorite Types
Authors: Herndon J. M.
Published: July 2016

The minerals of chondritic meteorites, particularly C2 and C3 are usually believed to be condensates of the (previously unfractionated) solar nebula. This implies two postulates: (1) that chemical reactions between phases ceased at various temperatures; (2) that Ni and Fe were mobilized by diffusion in the solid state. An alternate explanation is proposed, which obviates the two postulates: chondritic minerals may have condensed, in equilibrium with their own vapors, from a fraction already separated from the solar nebula at low temperature and low pressure.
Spectral Observations of the Diffuse FUV Background with DUVE (the Diffuse UV Experiment)
Authors: Korpela Eric J. , Bowyer Stuart
Published: July 2016

We present results from a search for FUV emission from the diffuse ISM conducted with an orbital FUV spectrometer, DUVE, which was launched in July, 1992. The DUVE spectrometer, which covers the band from 950 Å to 1080 Å with 3.2 Å resolution, observed a region of low neutral hydrogen column density near the south galactic pole for a total effective integration time of 1583 seconds, the only emission line detected was a geocoronal hydrogen line at 1025 Å . We were able to place upper limits to several emission features that provide constraints to interstellar plasma parameters. We were also able to place continuum limits in this band. We use these upper limits to place constraints upon the emission measure vs. temperature distribution of this gas using an isothermal Landini and Fossi model.
The Structure of the Local Hot Bubble Toward l = 165°, b = 0° Using IUE and ROSAT Data
Authors: de Boer K.S. , Kerp J.
Published: July 2016

The first X-ray-opaque cloud in the direction of Auriga lies at 180 pc. A tenuous cloud, whose distance is derived from IUE absorption line studies as well as from an analysis of ROSAT data, is embedded at 55 pc. The X-ray emitting gas has a temperature of 105.9−6.0 K. The pressure is 1.6 104 K cm−3.
D/H-Ratio: Observations with ORFEUS II
Authors: Gölz M. , Kappelmann N. , Appenzeller I. , Barnstedt J. , Fromm A. , Grewing M. , Gringel W. , Haas C. , Hopfensitz W. , Krämer G. , Krautter J. , Lindenberger A. , Mandel H. , Werner K. , Widmann H.
Published: July 2016

During the second flight of the ORFEUS-SPAS satellite (Nov./Dec. 96) high resolution (λ/∆λ = 10,000) Echelle-spectra of BD+28° 4211 in the wavelength regime 912–1400 Å have been taken. Deuterium can be clearly identified in the ORFEUSII Echelle-spectra of this star. For the first time it was possible to take spectra of faint, not redshifted objects in the far ultraviolet with a sufficient spectral resolution to study the deuterium column density in the whole spectral range of the Lyman-series down to the Lyman-limit. We obtained a value of log(ND) = 14.7 (±0.3) towards BD+28° 4211. The hydrogen column density has been determined using ORFEUS Echelle- and IUE-spectra of Ly-α (log(NH) = 19.8 (±0.2)). Thus a value of 8 × 10−6 can be obtained for the D/H-ratio on the line-of-sight towards BD+28° 4211.
High-Resolution Optical Observations of Diffuse Clouds
Authors: Welty Daniel
Published: July 2016

We describe results from high-resolution (Δv = 0.3-1.5 km s−1) observations of absorption lines due to interstellar Na I, Ca II, K I, Ca I, and Ti II. At those resolutions, we can identify and characterize many (but not all) of the individual clouds along a given line of sight; complex spatial and/or velocity structure appears to be the norm. Both the spectra and the statistics of individual cloud properties derived from fits to the observed line profiles suggest that: 1) the five species are not entirely coextensive in the neutral ISM; 2) the typical separation between adjacent components (in Na I and Ca II) is ~1.2 km s−1; 3) the median line widths (FWHM) for components in Na I, K I, and Ca I are ≾ 1.2 km s−1; 4) larger line widths for Ca II, even for “corresponding” components at similar velocities, suggest that Ca II is more widely distributed; 5) line widths for clouds in the Galactic halo and in the local ISM (within 100 pc) are generally somewhat larger than for clouds in the general Galactic disk; and 6) components with very different properties (line width, relative abundances, overall column densities) are often separated by only several km s−1. Observations of multiple systems and lines of sight in restricted regions reveal complex spatial structure and velocity coincidences even within 100 pc. These high-resolution optical spectra can be used to model lower resolution UV spectra of many other neutral and singly ionized species, enabling abundances and physical properties to be derived for individual interstellar clouds.
Diffuse Ionized Gas in the β CMa Tunnel
Authors: Dupin Olivier , Gry Cécile
Published: July 2016

We present HST observations of the interstellar medium toward the star β CMa known to be located in a low density extension of the Local Bubble. Most of the matter in the sight-line is ionized and clumped in two main components. One of them, as well as one of the components detected toward ϵ CMa, is mostly ionized and only slightly depleted. Their ionization ratios are compatible with collisional ionization at T~25 000 K. These clouds could have been ionized by shocks related to the Local Bubble creation and also responsible of some dust grain sputtering.
Energetic Particles in the Local Bubble
Authors: Morfill G.E. , Freyberg M.J.
Published: July 2016

The current status of observations of energetic particles in the “local bubble” is reviewed. This includes primarily “direct” measurements of cosmic rays made in the Solar System, but also the “remote sensing” made possible by observing cosmic ray produced γ-rays in the nearby interstellar clouds. Since the energetic events responsible for the formation of our local bubble may also have produced copious amounts of cosmic rays, fossil records are examined to determine whether there is a corresponding signature. The observations show that: 1) the cosmic ray (proton) intensity is fairly homogeneous throughout the local bubble and its adjacent interstellar clouds, 2) there is some evidence for a “recent” local cosmic ray injection about 40,000 years ago, 3) on longer time scales (a few million years) the cosmic ray intensity was constant within a factor two, 4) there is apparently some “activity” in the Orion cloud, as evidenced by low energy γ-ray signatures, and 5) there are two unexplained observations – the variations in the energy spectra, in particular the significantly flatter spectrum of heavy cosmic rays (Fe) and the matter path length variation, which yields consistently larger path lengths for the lighter elements (H, He). It is suggested that these observations are compatible with two cosmic ray populations – an older one in equilibrium with losses from the galaxy and a younger one which is not yet strongly affected by losses. The latter could be a cosmic ray signature of the formation of the local bubble.
Study of the LISM Using Pulsar Scintillation
Authors: Bhat N.D.R. , Gupta Y. , Rao A.P.
Published: July 2016

We present here the results from an extensive scintillation study of twenty pulsars in the dispersion measure (DM) range 3 – 35 pc cm−3 carried out using the Ooty Radio Telescope, to investigate the distribution of ionized material in the local interstellar medium (LISM). Our analysis reveals several anomalies in the scattering strength, which suggest that the distribution of scattering material in the solar neighborhood is not uniform. Our model suggests the presence of a low density bubble surrounded by a shell of much higher density fluctuations. We are able to put some constraints on geometrical and scattering properties of such a structure, and find it to be morphologically similar to the local bubble known from other studies.
Interstellar Scintillation of Radio Sources as a Probe for Investigations of the Local Interstellar Medium
Authors: Bochkarev N. , Ryabov M.
Published: July 2016

A possibility of obtaining information on small scale inhomogeneities of the electron component of the local interstellar medium (LISM) is investigated using interstellar scintillations of extragalactic radio sources. We analyse Culgoora array observational data on variability of 190 extragalactic radio sources, covering most of the sky, at 80 and 160 MHz. The variability at time scales from 1 month to 15 years is interpreted as refractive interstellar scintillations in fast-moving nearby (less than 150 pc) hot gas near shock waves in the LISM. All-sky map of scintillation indices m averaged over 3–5 sources closest to one another shows several m maxima. Two of the 3 most pronounced maxima are probably connected with Loop I; the third one coincides with the soft X-ray (0.1–0.3 keV) background maximum near the South Galactic Pole. Other, less certain, m maxima probably correspond to the Orion star-formation region and to a soft X-ray maximum near the North Galactic Pole. The ”free-of-gas” tunnel in the direction l = 240° corresponds to low values of m. The estimated time scale of interstellar scintillations on the above-mentioned LISM structures is in agreement with that of the observed radio-source variations.
The Local Bubble, Local Fluff, and Heliosphere
Authors: Frisch Priscilla C.
Published: July 2016

The properties of the Local Bubble, Local Fluff complex of nearby interstellar clouds, and the heliosphere are mutually constrained by data and theory. Observations and models of the diffuse radiation field, interstellar ionization, pickup ion and anomalous cosmic-ray populations, and interstellar dust link the physics of these regions. The differences between the one-asymmetric-superbubble and twosuperbubble views of the Local Bubble are discussed.
Fluctuations in the Diffuse Soft X-ray Background; Probably of Galactic Halo Origin
Authors: Sumner T.J. , Sidher S.D. , Quenby J.J. , Hernandez M. , Mian A. , Jesseit R. , Gambhir M.
Published: July 2016

Soft X-ray background data from the ROSATPSPC have been fitted by a model including emission from the local bubble, embedded hot gas within the disk, hot gas in the Galactic halo and extra-galactic emission, together with local and disk absorption. In all directions a halo component at 106.2 K (0.2 keV) is required for an acceptable fit. The halo emission measure shows spatial variability and the global trend suggests a disk-like planar rather than more extended spherical distribution. New values for the emission measure within the local bubble are derived.
Infrared Emission from Interstellar Dust in the Local Interstellar Medium
Authors: Reach W.T. , Boulanger F.
Published: July 2016

In this contribution, we discuss some topics in the study of dust in the local interstellar medium. The spectrum of local clouds has recently been measured using ISO and COBE, confirming in general the models of excitation and cooling of dust illuminated by the the interstellar radiation field. We discuss in some detail the spatial correlation of interstellar dust and gas and the idea that infrared emission traces the total column density of the interstellar medium, with the particular application to the formation of H2. We also show that dust is present in the nearby Loop I shell, with properties similar to average, suggesting that the walls of the Local Bubble would also have relatively ‘normal’ dust content.
Optical Studies of a Local Filament Toward the Magellanic Clouds and a Local IVC Region
Authors: Penprase B.E. , Wang Q.D. , Herbstmeier U.
Published: July 2016

We present new spectroscopic results which constrain the distance of a large IR emitting filament near the LMC, as well as some new results for a local region with widely distributed detections of Intermediate Velocity Clouds (IVCs). We present spectroscopic observations of stars toward both regions which constrain the distances and kinematics of the interstellar features. New optical high resolution (λ/δλ ⋍ 106) spectra have been obtained for the star HD 22252, and are used to estimate approximate distances, temperatures, and pressures within the cloud. An unusual local region of the interstellar medium with several IVCs is also reported, with multiple components of absorption from -80 < υLSR < 70 km s−1 seen toward several stars in the region.
High-Velocity Clouds and their Soft X-ray Emission
Authors: Kerp J. , Pietz J. , Kalberla P.M.W. , Burton W.B. , Egger R. , Freyberg M.J. , Hartmann Dap , Mebold U.
Published: July 2016

Diffuse excess ¼ keV soft X-ray emission was found to be positionally correlated with the column density distribution of the high velocity cloud (HVC) complex C (Kerp et al. 1996). Here we point out that the detected diffuse X-ray emission is indeed associated with the HVC phenomenon. For this purpose we study the ¼ keV radiation transfer as well as the H I column density distribution of HVCs and intermediate velocity clouds (IVCs) towards HVC complex C in detail. We present evidence that on arcmin scales the ¾ keV soft X-ray emission is positionally anticorrelated with the HVC column density distribution of an individual HVC filament of complex C.
The Hot Galactic Corona and the Soft X-ray Background
Authors: Daniel Wang Q.
Published: July 2016

I 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

Over 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

Observational 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

Polarization 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

Numerous 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.
Radiation-Driven Disk Winds
Authors: Drew Janet E. , Proga Daniel , Oudmaijer René D.
Published: July 2016

Recent work on numerical modelling of radiation-driven disk winds is summarised and discussed in the context of extreme B emission line stars.
UV Wind Variability in B Supergiants and its Implications for Wind Structures
Authors: Massa Derek , Prinja Raman K.
Published: July 2016

We 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

The 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

O 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

The 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

Migration 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

The 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

Analytical 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.
Dynamics of Real Asteroid at the Hecuba Gap
Authors: Roig F. , Ferraz-Mello S.
Published: July 2016

We study the dynamics of real asteroids at the 2/1 resonance with Jupiter, and find that Griqua-like objects have a short life-time inside the resonance, while Zhongguo group can survive for many 108yr.
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

The 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 whether

for 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).
Symbiotic Stars at Optical, Infrared and Radio Wavelengths
Authors: Allen David A.
Published: July 2016

No paper of this nature should begin without a definition of symbiotic stars. It was Paul Merrill who, borrowing on his botanical background, coined the termsymbioticto describe apparently single stellar systems which combine the TiO absorption of M giants (temperature regime ≲ 3500 K) with He II emission (temperature regime ≳ 100,000 K). He and Milton Humason had in 1932 first drawn attention to three such stars: AX Per, CI Cyg and RW Hya. At the conclusion of the Mount Wilson Ha emission survey nearly a dozen had been identified, and Z And had become their type star. The numbers slowly grew, as much because the definition widened to include lower-excitation specimens as because new examples of the original type were found. In 1970 Wackerling listed 30; this was the last compendium of symbiotic stars published.
The Interpretation of Radial Velocity Observations of Long Period Variable Stars
Authors: Willson L. A.
Published: July 2016

The first part of this paper contains a synthesis of the results of numerical and analytical theoretical models for the velocity structure of the atmospheres of the long period variable stars (LPVs). The details of these derivations have been presented elsewhere (Willson and Hill 1978; Hill and Willson 1978). The discussion of the models in this paper is therefore limited to summarizing the earlier results in a form appropriate to the interpretation of observed velocities. In the second part of the paper the methods described in the first part are applied to five stars with periods ranging from 150dto 407d, and masses and radii are derived from velocity information for each of these stars. In the third section a general mass-radius relationship for the long period variable stars is derived from these points and compared to independent observational constraints.
About The Correlation between the Period and Dispersion of the Light Curve of Mira Type Variables
Authors: Garcia Jamie R.
Published: July 2016

During 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.
The Tilt of the Large Magellanic Cloud
Authors: Gascoigne S.C.B. , Shobbrook R.R.
Published: July 2016

Photoelectric light curves have been obtained for 20 Cepheids, 12 on the far western side of the LMC and 8 on the far eastern side. The difference between the moduli of the two groups is 0.12 ± 0.05 mag., the western side being 3 kpc more distant than the eastern.
Double-Mode Dwarf Cepheid Periods and Masses
Authors: King David S. , Cox Arthur N.
Published: July 2016

Approximately one dozen of the known dwarf Cepheids (AI Velorum stars) with periods ranging from about 0ḍ05 to 0ḍ22 are found to be simultaneously excited in two modes. Table 1 lists these variables along with their longest period and the period ratio, here assumed to be Π1/Π0. The other data in this table will be discussed in Section III. The observational data are taken from Fitch and Szeidl (1976) and Percy (1976)(for 21 Com and ZZ Mic).
The Light Variation of the Eclipsing System Di Pegasi
Authors: Kennedy Harold D.
Published: July 2016

The discovery of the variability of DI Peg can be attributed to Morgenroth (1934). The same year Jensch (1934) published a photographic light curve. The variable has been recognized as an eclipsing binary of the 6-Lyrae type. Rucinski (1967) analysed photoelectric observations made by Kruszewski in 1961 and derived an orbital solution. In 1968 and 1969 Binnendijk(1973) obtained a total of 1165 observations in yellow and blue light at Flower and Cook Observatory. He concluded from his results that the secondary minimum was somewhat wider than the results of Rucinski had indicated.
Microprocessor Controlled Photometer to Observe Rapidly Changing Variable Stars
Authors: Freeth R.V. , Griffiths B. , Tan Z.C.
Published: July 2016

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.’