bluuebunny/crossref_metadata_2025 huggingface dataset:
The Libration Points and Hill Surfaces in the Restricted Problem of Three Variable-Mass Bodies
Authors: Bekov A.A.
Published: July 2016

The paper deals with the study of the arising and disappearence of collinear (Eulerian) L1, L2, L3, triangular (Lagrangian) L4, L5, coplanar L6, L7, ring L0 and infinitely distant L±∞ solutions in a restricted problem of three variable-mass bodies for different time dependencies of main bodies masses and for some additional conditions imposed on the systems parameters. In this case it is assumed that the motion of variable-mass main bodies is determined by the Gylden-Mestschersky problem. The Bill surfaces in the restricted three-body problem where main bodies masses variate isotropically according to the Mestschersky law are studied. Certain possibilities of applying the results of investigations to nonstationary double stellar systems are discussed.
New Intermediaries for the Main Problem in Satellite Theory
Authors: Ferrándiz José M. , Floría Luis
Published: July 2016

After reviewing the original approach leading to the introduction of intermediaries in Satellite Theory, a general procedure to define intermediaries for the Main Problem in this Theory is proposed. This procedure is susceptible to an intuitive interpretation analogous to solving a simple puzzle. The application of this method to the Main Problem allows us not only to recover the well known classical intermediaries but also to obtain several completely new ones, all admitting simple solutions.
The Infrared Spectra of Synthesized Amorphous Silicates with Compositions of Olivine and Pyroxene
Authors: Koike Chiyoe , Tsuchiyama Akira
Published: July 2016

Amorphous olivines synthesized by evaporation method show two very broad bands at 10-11 μm and 17.5-19 μm, which resemble the spectra of symbiotic stars. On the other hand, amorphous pyroxenes produced by the same method show two broad bands at 9.5-10.3 μ and 20-22 μ which are narrower than that of amorphous olivine. The features of amorphous olivine were easily altered by heating or hydration, and the peak wavelength of 18 μm band was easily shifted to longer wavelengths.
Light Scattering by Dust Particles in the Outer Solar System
Authors: Hovenier J.W. , Bosma P.B.
Published: July 2016

Photometric observations of the zodiacal light performed by Pioneer 10 indicated that there may be very little scattering by dust in the outer solar system. To shed more light on this problem we formulate explicit expressions for interpreting the brightness observed by a spacecraft travelling inside or outside a finite homogeneous cloud of scattering particles. An application is made to the ecliptic zodiacal light brightness as observed by Pioneer 10 and tabulated by Toller and Weinberg (1985). A satisfactory interpretation of these data as well as earthbound observations can be given by means of a model having a particle density distribution or mean scattering cross section which vanishes beyond 2.8 - 3.7 AU. Some implications for the nature and spatial distribution of the interplanetary dust are discussed.
Comets as a Source of Interplanetary and Interstellar Grains
Authors: Hoyle F. , Vickramasinghe N.C.
Published: July 2016

Properties of cometary dust with regard to bulk density, optical characteristics and sizes, derived from recent observations, are used to model scattering properties of cometary and interstellar grains. A wide range of astronomical observations are shown to be explained if cometary objects are hypothesised as a major source of dust grains in the galaxy.
Spectropolarimetry of Comet Halley
Authors: Visvanathan N. , Meglick Z. , Wickramasinghe D.T.
Published: July 2016

Spectropolarimetric observations from 3800 to 7000 Å were obtained for the nucleus of comet Halley for nine nights during 1985-86. The observations were spaced over phase angle of 2 to 66 °. The continuum polarization without molecular-line contamination as well as the polarization of the molecular lines were evaluated. The plot of polarization versus the phase angle shows small negative polarization for angles less than 20°. The highest polarization measured for phase angle ≤ 66° is 19.6% .The lowest polarization of −2.0% has been measured at the phase angle ~ 10°. The variation of polarization with phase angle is nearly linear in the range 30 to 60° giving a slope of 0.4316% per degree. There is small dependence of polarization with the wavelength in the region 3800 to 6500Å. The polarization of the molecular bands CN, C3, C2(0,0) and C2(1,0) have also been evaluated for the spectra of 15th December 1985, 18th and 19th March 1986 and 8th April 1986.
The Orbital Distribution and Origin of Meteoroids
Authors: Steel Duncan
Published: July 2016

Approximately 68,000 orbits of meteoroids, ranging from sizes of 10 cm and more down to microgram masses, are now available through the IAU Meteor Data Center. These orbits were measured in surveys based in the U.S.S.R., the U.S.A., Canada, Somalia, and Australia, using photographic, radar and television techniques; the data represent our best knowledge of the orbital distributions of smaller solid bodies in the solar system. It is found that quite different distributions result in different mass regimes, with implications for the origin and evolution of these particles: for example the larger bodies, observed as fireballs, are associated with meteorites in coming from the region of the asteroid belt with low-inclination orbits, whereas the smaller meteoroids have more comet-like orbits. There is also evidence for several meteoroid streams associated with specific Apollo asteroids. The data may additionally be viewed as a suitable source function in investigations of the production of interplanetary dust from the fragmentation of larger meteoroids in mutual collisions. However, inspection of the data raises many questions: for instance there seem to be many meteoroids on small retrograde paths, but no possible parent objects are known to exist on such orbits.
η Lyrid Meteor Stream Associated with Comet Iras-Araki-Alcock, 1983 VII
Authors: Ohtsuka K.
Published: July 2016

The probable association of Comet IRAS-Araki-Alcock with theηLyrid meteor stream is suggested, and the possible relation of the radio meteor shower on 1983 May 10 is also discussed.
Laboratory Studies of Grain Mantles in Interstellar Space
Authors: Mendoza-Gomez C.X. , Greenberg J.M.
Published: July 2016

At Laboratory Astrophysics we are simulating the most relevant conditions in interstellar space in order to follow the chemical and physical evolution of, among others, interstellar organic grain mantles.
Evolution of Galaxies Governed by Disk Dynamics and Spiral Structure
Authors: Talbot Raymond J.
Published: July 2016

My major topic will be the evolutionary changes in disk galaxies caused by the continuing process of star formation. The task of interpreting observations to derive the past rate of star formation is treacherous, as I am sure will be evident in the various observational papers presented at this colloquium. Therefore, I will mention only briefly some of the basic aspects of models which have been used to discuss that past evolution.
Vertical and Radial Distributions of Gas and Young Objects in the Galaxy and the Schmidt’s Law of Star Formation
Authors: Guibert J. , Lequeux J. , Viallefond F.
Published: July 2016

The thickness of the disc distribution of young objects is shown to be significantly smaller than that of the interstellar gas over the whole Galaxy, as predicted by the Schmidt’s law of star formation. The radial distribution of the density of young objects at z = 0, compared with that of the gas, is also consistent with the Schmidt’s law. The exponent in this law is found to be between 1.5 and 2. A brief discussion of simple models of galactic evolution using the Schmidt’s law is made.
Interaction between the Galactic Disk and Halo Components
Authors: Ostriker Jeremiah P.
Published: July 2016

At least three component parts of the galaxy must be recognized. TheDisk Componentof the galaxy might be defined as follows. Spatially it is largely confined between the planes ± 1 kpc from the plane of symmetry. With regard to velocities, it is acoldsubsystem in that the random motions within it (~ 20 km/s) are small compared to the systematic flow of rotational motion (~ 200 km/s). Finally, its composition is largely stellar with stars of all ages and masses being present. Few galaxies are known where the ratio of (gas/stellar) mass is > 10% (cf. Roberts 1975a), and the metal abundance is typically high with at most one percent of the stars having metallicity less than 1/4 that of the Sun (cf. Schmidt 1963). From this point of view the spiral parts are a relatively unimportant (in terms of mass and composition) sub-part of the disk system.
Possible Pattern Speeds of a Density Wave in our Galaxy
Authors: Grosbøl Preben J.
Published: July 2016

Since the density wave theory was introduced by Lin and Shu (1964) to explain the spiral structure considerable effort has been made to detect this kind of wave in our galaxy and to determine its parameters. Observations of the distribution and velocity field of gas and young objects show the present shape and location of the spiral pattern in our galaxy but tell little about its angular velocity. It was proposed by Strömgren (1967) to estimate this important parameter by calculating the places of formation of moderately young stars for which accurate space velocities and ages are known. This was done assuming that the majority of stars is formed in spiral arms so that the stellar birthplaces would outline the position of the spiral pattern at different epochs. Later, Yuan (1969) and Wielen (1973) calculated stellar birthplaces in the spiral potential given by Lin et al. (1969). These investigations showed no disagreement with the assumed density wave, however, the number of stars was too small to verify the assumed pattern speed.
The Kamiokande Solar Neutrino Experiment
Authors: Hirata K. S. , Kajita T. , Kifune T. , Kihara K. , Nakahata M. , Nakamura K. , Ohara S. , Sato N. , Suzuki Y. , Totsuka Y. , Yaginuma Y. , Mori M. , Oyama Y. , Suzuki A. , Takahashi K. , Takei H. , Tanimori T. , Koshiba M. , Suda T. , Tajima T. , Miyano K. , Miyata H. , Yamada M. , Fukuda Y. , Kaneyuki K. , Nagashima Y. , Takita M. , Beier E. W. , Feldscher L. R. , Frank E. D. , Frati W. , Kim S.B. , Mann A. K. , Newcomer F.M. , Van Berg R , Zhang W.
Published: July 2016

The observation of 8B solar Neutrinos in the Kamiokande-II detector is presented. Based on 450 days of data in the time period of January 1987 through May 1988, the measured flux obtained with Ee ≥ 9.3 MeV was 0.46 ± 0.13 (stat) ± 0.08 (sys) of the value predicted by the standard solar model. The detector and analysis methods were improved since June 1988 and the background level has been decreased by a factor of about three since then.
The GALLEX Project
Authors: Kirsten T. , Breitenbach M. , Hampel W. , Heusser G. , Kiko J. , Kirsten T. , Lalla H. , Lenzing A. , Pernicka E. , Plaga R. , Povh B. , Schlosser C. , Völk H. , Wink R. , Zuber K. , Ammon R.v. , Ebert K. , Henrich E. , Stieglitz L. , Bellotti E. , Cremonesi O. , Fiorini E. , Liguori C. , Ragazzi S. , Zanotti L. , Mössbauer R. , Urban A. , Berthomieu G. , Schatzman E. , d’Angelo S. , Bacci C. , Belli P. , Bernabei R. , Paoluzi L. , Santonico R. , Cribier M. , Dupont G. , Pichard B. , Rich J. , Spiro M. , Stolarczyk T. , Tao C. , Vignaud D. , Dostrovsky I. , Friedlander G. , Hahn R.L. , Rowley J.K. , Stoenner R.W. , Weneser J.
Published: July 2016

The GALLEX collaboration aims at the detection of solar neutrinos in a radiochemical experiment employing 30 tons of Gallium in form of concentrated aqueous Gallium-chloride solution. The detector is primarily sensitive to the otherwise inaccessible pp-neutrinos. Details of the experiment have been repeatedly described before [1-7]. Here we report the present status of implementation in the Laboratori Nazionali del Gran Sasso (Italy). So far, 12.2 tons of Gallium are at hand. The present status of development allows to start the first full scale run at the time when 30 tons of Gallium become available. This date is expected to be January, 1990.
The Baksan Gallium Solar Neutrino Experiment
Authors: Gavrin V. N. , Abazov A. I. , Abdurashitov D. N. , Anosov O. L. , Bychuk O. V. , Danshin S. N. , Eroshkina L. A. , Faizov E. L. , Gavrin V. N. , Gayevsky V. I. , Girin S. V. , Kalikhov A. V. , Kireyev S. M. , Knodel T. V. , Knyshenko I. I. , Kornoukhov V. N. , Mezentseva S. A. , Mirmov I. N. , Ostrinsky A. V. , Petukhov V. V. , Pshukov A. M. , Revzin N. E. , Shikhin A. A. , Slyusareva E. D. , Tikhonov A. A. , Timofeyev P. V. , Veretenkin E. P. , Vermul V. M. , Yantz V. E. , Zakharov Yu. I. , Zatsepin G. T. , Zhandarov V. L. , Bowles T. J. , Cleveland B. T. , Elliott S. R. , O’Brien H. A. , Wark D. L. , Wilkerson J. F. , Davis R. , Lande K. , Cherry M. L. , Kouzes R. T.
Published: July 2016

A radiochemical 71Ga−71 Ge experiment to determine the integral flux of neutrinos from the sun has been constructed at the Baksan Neutrino Observatory in the USSR. Measurements have begun with 30 tonnes of gallium. The experiment is being expanded with the addition of another 30 tonnes. The motivation, experimental procedures, and present status of this experiment are presented.
Neutrino Masses, Neutrino Oscillations and Dark Matter
Authors: Harari Haim
Published: July 2016

We discuss bounds on neutrino masses using an analysis based on direct measurements, cosmological bounds, oscillation experiments, the solar neutrino puzzle and theoretical considerations on neutrino decays. We present four possible solutions for the mass range of the three neutrino flavors. We outline experiments which can distinguish among these solutions and discuss their implications for the cosmological dark matter problem.
Variations of the Low l Solar Acoustic Spectrum Correlated with the Activity Cycle
Authors: Pallé P.L. , Régulo C. , Roca Cortés T.
Published: July 2016

Solar cycle variation of the frequencies and of the power of solar acoustic oscillations are investigated. Integrated sunlight data from 1977 to 1988 obtained at the Observatorio del Teide (Izaña, Tenerife), using a resonant scattering spectrophotometer, is analyzed in 60 day time strings and their power spectra are calculated from 2 to 3.8 mHz. To study the frequency variation, each power spectrum is cross-correlated with the one corresponding to the 1981 series and the shifts of the centroids of the cross-correlation peaks are calculated. The results show a clear variation in frequency of the cross-correlation peaks of −0.37 ± 0.04 μHz peak to peak as solar activity cycle goes from maximum to minimum. Moreover, this effect is found to depend on the l value of the modes, being absent for l = 0 and of 0.42 ± 0.06 μHz for l = 1. These results can be interpreted as an amplitude modulation between modes of the same multiplet, probably as a consequence of the action of strong magnetic fields. As low l modes penetrate deeply into the Sun’s interior, these observations suggest changes in its structure correlated with the solar activity cycle. When the power of the modes is calculated, using the same series as before, and its change along the solar cycle is studied, a variation of ~ 40% is found, the power being higher when solar activity is at its minimum. If this effect is independent of the l value of the p-modes, the results can be interpreted in terms of a change in the efficiency of the excitation mechanism of such modes. Indeed, if turbulent convection is such a mechanism, a change in the characteristic size of the granulation would account for the observed effect. Alternatively, another explanation could be a selective change in the efficiency of the excitation and/or damping mechanisms of the l ≤ 3 modes in front of other l value modes.
On the Postoutburst Far Ultraviolet Declines of WZ Sagittae and V1500 Cygni
Authors: Sion Edward M. , Szkody Paula
Published: July 2016

In an earlier paper [1], we demonstrated that the declining ultraviolet flux, observed long after optical quiescence was reached in three dwarf novae, most likely represents the cooling of a white dwarf whose outer layers have been heated by the accretion event. If the observed change in temperature is due to the cooling of the white dwarf surface layers following the intense heating produced in the outburst, then a thermal timescale of the heated portion of the white dwarf is implied, which could yield a rough estimate of the depth of heating into the white dwarf envelope. The thermal timescale is essentially given by the ratio of the internal energy in the affected layers to their luminosity, L.
The Early Outburst Spectra of Nova V1500 Cygni
Authors: Mikołajewski M. , Mikołajewska J.
Published: July 2016

Nova Cygni 1975 (V1500 Cyg) was outstanding in several respects. It was the most luminous galactic nova ever observed, had the largest outburst amplitude, and had the fastest evolution with time.

The spectra, with dispersion 28 A/mm and in spectral range λλ3560-5055 A, were obtained with the CCS spectrograph on 90 cm reflector at Toruń Observatory by the research group supervised by prof. A. WoszczyK. The CCS spectrograph was equipped with the 3.5 arcsec aperture Richardson’s image slicer and stars with known spectral energy distributions were observed on each night, so we were able to derive absolute energy distributions for the V1500 Cyg spectra. The calibration of the energy scale was performed by comparing synthetic B magnitudes calculated from our spectra with numerous published B photometry of the nova. The first spectra were obtained about 3h later than spectra reported by Boyarchuk (1977) and about 6h earlier than spectra discussed by Duerbeck and Wolf (1977); thus they are among the earliest spectra of the nova available. Simultaneously, the spectra correspond to the earliest state of spectral evolution of a nova ouburst yet observed. The pre-maximum spectral evolution of Nova V1500 Cyg is extremely fast. The spectra (Figures 1 and 2) secured on JD 2442654 are characterized by a very strong continuum and broad blueshifted absorption lines of OII, NII and CII of unusual strengths, as well as the Balmer series and Hel.
Model Atmospheres for Novae During the Early Stages
Authors: Wehrsě R. , Hauschildt P. H. , Shaviv G. , Starrfield S.
Published: July 2016

Continuum and line blanketing models for the photospheres of novae in the early stages of their outbursts are presented. The expanding envelopes are characterized by a very slow increase of density with decreasing radius which leads to very large geometrical extensions and large temperature differences between the inner and outer parts. The spectra show a large IR excess and a small Balmer jump which may be either in absorption or in emission. For the parameters considered (Teff = 104, 1.5 × 104, 2 × 104K, R = 1011 cm, solar composition), most lines are in absorption. The effects of both modifications in the temperature structure (e.g. by heating from shock fronts) and changes in the abundances of the heavy elements on the emergent spectra are briefly discussed.
Modelling the Common Envelope Phase in Classical Novae
Authors: Shankar Anurag , Truran James W. , Burkert Andreas , Livio Mario
Published: July 2016

Preliminary results of 1– and 2– dimensional hydrodynamical calculations of the common envelope phase in very slow classical novae are presented. We show that frictional deposition of orbital energy and angular momentum into the envelope can potentially induce mass loss. Specifically, we find that despite rapid initial spin–up of the envelope, ejection of mass in the orbital plane continues at a substantial rate.
Theoretical Implications of Nova Abundances
Authors: Truran James W.
Published: July 2016

Abundance determinations for the ejected shells of classical novae are reviewed. Substantial enrichments (relative to hydrogen) of helium, the CNO elements, and elements in the range from neon to aluminum are found to be characteristic of nova ejecta. The source of these enrichments is believed to be the dredge-up of underlying white dwarf core matter, thus reflecting the white dwarf composition and confirming the presence of oxygen-neon-magnesium (ONeMg) as well as carbon-oxygen (CO) degenerate dwarfs in cataclysmic variable systems. The implications of these abundance enrichments, for the behavior of nova systems in outburst and for nucleosynthesis, are examined.
Diffusion in Novae at High Accretion Rates
Authors: Kovetz Attay , Dina Prialnik
Published: July 2016

The main outstanding problem in our full understanding of the classical nova mechanism is the apparent discrepancy between mass transfer rates (10−9 to 10−8M⊙/yr) inferred from observations (Patterson, 1984, Ap.J.Suppl.231, 789), and those required by numerical models in order to reproduce nova characteristics (10−11 to 10−9M⊙/yr). The low accretion rates are needed in order to obtain powerful runaways and high values of Z in the ejecta by the diffusion-convection mechanism. The discrepancy seems to have sharpened by the realization that accretional heating (Shaviv and Starrfield, 1987, Ap.J.321, L51) and angular momentum transfer (Sparks and Kutter, 1987, Ap.J.321, 394 and Kutter and Sparks, 1987, Ap.J.321, 386) tend to lower the theoretical upper limit for Ṁ to about 10−10M⊙/yr. On the other hand, scenarios invoking variable mass accretion rates — hibernation (Shara et al, 1986, Ap.J.311, 163) or ‘mild’ hibernation (Livio, Shankar and Truran, 1988, Ap.J.330, 264) — have shown that the high observed rates immediately prior and following outbursts can be reconciled with lower average accretion rates over the period between outbursts.
The 1989 Outburst of V404 Cygni: A Very Unusual X-Ray Nova
Authors: Wagner R. M. , Starrfield S. , Cassatella A. , Gonzalez-Riestra R. , Kreidl T. J. , Howell S. B. , Hjellming R. M. , Han X.-H. , Shrader C. , Sonneborn G. , Collins G. W. , Bertram R. , Buie M. W. , Bond H. E. , Johnson J. , Harrison T. , Gehrz R. D. , Córdova F. A. , Szkody P. , Margon B. , MacDonald J. , Fried R.
Published: July 2016

On May 22, 1989 the Japanese Ginga Team discovered a new X-ray source that was cataloged as GS 2023+338. This source was subsequently identified as coincident in position with a previously known nova cataloged as V404 Cygni. Its last recorded outburst was in 1938 when it rose to about 12th mag. Spectroscopic data were obtained and confirmed the nature of the outburst. Additional ground based data were obtained by us at CTIO and the VLA. The X-ray behavior of this object has been reported to be very unusual and it reached a peak of about 17 crab about one week after discovery. Since then it has varied widely in magnitude at all wavelengths at which it has been studied. We present a brief summary of the observations that have been obtained up to the time of the meeting and shortly thereafter.
The Structure of the Envelopes of Symbiotic Novae
Authors: Baratta G.B. , Neto A. Damineli , Rossi C. , Viotti R.
Published: July 2016

Symbiotic novae are composite spectrum stars whose light history is characterized by one single major outburst. At high resolution their optical and UV spectra are very rich of emission lines belonging to a wide ionization range. Generally one can identify both narrow and broad line systems. The latter includes emission lines with multiple structure, broad emission wings, WR features, and P Cygnl lines. Frequently the broad line profiles are largely variable with time. They should be associated with the major stellar outburst. An overview of the problem with extensive references can be found in Viotti (1989).
Recent Observations of the Highly Variable Stab DR Tau
Authors: Bertout C. , Krautter J. , Möllenhoff C. , Wolf B.
Published: July 2016

Simultaneous spectroscopic and photometric observation of the T Tau-like star DR Tau are reported. The spectrograms show a rich emission spectrum. The Balmer lines are strongly variable. They sometimes show a highly complex structure, and inverse P Cygni profiles were observed on two nights. The metallic lines are essentially undisplaced. Simultaneous photometry indicates irregular variations of the blue continuum by as much as 0.5 magnitude on a time-scale of one day and variations of more than two magnitudes on a time-scale of a few days. The observed spectral properties can be explained by assuming that DR Tauri is a protostar of about 1 M⊙ which has not yet reached its hydrostatic equilibrium Hayashi track.

A more complete description of our results is in press in Astronomy and Astrophysics.
Radio Emission from Close Binary Systems and Novae
Authors: Hjellming R.M.
Published: July 2016

This review of the radio emission properties of close binary systems and novae will be partly concerned with surveying the star systems that exhibit continuum radio emission, and partly concerned with discussing the implications of the observed radio emission. The phenomena we will encounter will range from purely thermal continuum radio emission for the case of ionized nova shells to strong, non-thermal continuum radio emission produced by relativistic particles in both ‘normal’ and X-ray emitting close binary systems. In keeping with the subject of this symposium, let me emphasize that all regions involving radio emission are from the portions of the stellar environment where Ne ≤ 1010cm-3, generally rather high in the stellar or systemic atmosphere; however, events more closely associated with the stars themselves are the root causes of the phenomena, supplying energy, mass, magnetic fields, and relativistic particles.
Stability of Accreting White Dwarfs in Close Binary Systems
Authors: Sienkiewicz R. , Dziembowski W.
Published: July 2016

We present results of thermal and vibrational stability analysis for 1 M⊙ white dwarf models corresponding to various accretion rates ≳ 10−11 M⊙/y. Accretion is assumed to be spherically symmetric and stationary. Thermal instability due to nuclear burning of hydrogen (at lower accretion rates) and helium (at higher rates) was found. At medium rates two growing thermal modes are simultaneously present. Vibrational instability was found for all models except those corresponding to highest accretion rates. The excitation rates for some nonradial g-modes are at least 3 orders of magnitude higher than those for radial pulsations. These rates are also higher than the excitation rates for thermal modes in certain range of accretion rates corresponding to high luminosities and effective temperatures. Among objects in which these instabilities may be important are symbiotic stars and nuclei of planetary nebulae.
4. Surface Phenomena in Simulated Cometary Nuclei
Authors: Dobrovolsky O. V. , Kajmakov E.
Published: July 2016

The sublimation or artificial icy cometary nuclei with different inclusions is investigated. Formation of meteoroids is discussed in connection with new polarizational observations of comet West. The possibility of chemical reactions on the sublimating surface is noted.
4. The Evolution of Comet Orbits as Perturbed by Uranus and Neptune
Authors: Everhart E.
Published: July 2016

When the perturbing planets are Uranus and Neptune, the perturbations on comets are so much weaker than with Jupiter and Saturn that a study of the comets’ orbital evolution, using exact numerical integration, would require 200 times more revolutions. This is hardly practical with present computers. Here we describe results with a simulation approach, the “Monte Carlo (random walk) method.” The proper distribution shape for the perturbations in energy are found from a few thousand numerical integrations, then this distribution of perturbations is applied to millions of simulated orbit-revolutions. This method reproduces earlier Jupiter results in 1/500 the former computation time. We find that Neptune can capture near-parabolic comets with perihelia in the range of 30 to 34 AU, increasing their 1/a-values and decreasing their perihelia until they reach a region where Uranus can interact. Uranus in turn passes some of these on to Saturn, who passes some to Jupiter. Ultimately a few reach the orbits of the visible short-period comets. The process requires about 200,000 comet orbit-revolutions, 4 × 108 years, and the efficiency is one in 6000. The rest of the comets are ejected on hyperbolic orbits.
2. The Chemical Composition of Cometary Meteoroids
Authors: Millman P. M.
Published: July 2016

Evidence for the chemical composition of cometary meteoroids is available from the spectra of shower meteors, from the analysis of extra-terrestrial dust particles, from a study of residues in the bottom of microcraters on plates exposed to the interplanetary environment, and from measures of the relative abundances of non-atmospheric ions in the E-region of the earth’s upper atmosphere. Quantitative measures of chemical abundances in meteoroids, based on the four techniques listed, show that in general the cometary meteoroids encountered by the earth conform to the carbonaceous chondrites type 1 in the case of the commonest metallic elements. There is also qualitative evidence of the presence of significant quantities of some of the light volatiles.
4. A Chemical and Textural Comparison between Carbonaceous Chondrites and Interplanetary Dust
Authors: Brownlee D. E. , Rajan R. S. , Tomandl D. A.
Published: July 2016

Interplanetary dust probably has a cometary origin. Collectible samples of this material are likely to be more representative of the meteoroid complex than are meteorites. Since 1974, NASA U-2 spacecraft has been able to collect over 200 interplanetary particles in the stratosphere. Roughly 10% have spheroidal shapes indicating previous melting. The rest seems to come from the gentle fragmentation of a single type of parent-body material: a black aggregate of grains mainly 1000 A in size, whose properties are closely similar to C1 and C2 chondritic material.
8. Quadrantid Meteor Shower: Eleven Years of Radar Observations
Authors: McIntosh B. A.
Published: July 2016

In studying the evolution of meteor streams from cometary debris it is desirable to know the distribution of particles both around the orbit and in the cross section perpendicular to the orbit. Earth-based observations are limited to a once-per-year sample and also limited by the position of the observer on earth as it crosses the meteor stream. A continuous series, 11 years, of records of the Quadrantid meteor shower illustrates the problems and the results that can be achieved. International cooperation would greatly assist such studies.
2. Asteroid Compositional Types and their Distributions
Authors: Zellner B. , Bowell E.
Published: July 2016

A sample of 359 minor planets with available colorimetric, spectropnotometric, thermal-radiometric, and/or polarimetrie data are classified into broadly defined compositional types C (carbonaceous), S (silicaceous), M (metal-rich), E (metal-free; enstatite?), O (ordinary-chondritic?), T (Trojan; unidentified composition), and U (unclassifiable; none of the above).

The small asteroids in Mars- or earth-crossing orbits are almost invariably of type S or O. For the main belt between 2.2 and 3.5 AU., distributions of the various types over diameter and orbital parameters are derived with corrections for observational selection bias. For 560 main-belt asteroids with diameters >50 km, 76% are of type C, 16% of type S, 5% M, and 3% of other types. The S objects become progressively less common with distance. The shapes of the diammeter-frequency relations for primitive (C) and evolved (S + M) types are statistically indistinguishable, both showing a change of slope at 160-km diameter.

While large asteroids avoid the Kirkwood gaps more strongly than small ones, we find no significant gap-related anomalies in the relative frequencies of compositional types. Thus most of the observational basis for models in which primitive and evolved asteroids respond differently to collisional evolution has been removed.
8. Asteroid Versus Comet Discrimination from Orbital Data
Authors: Kresak L.
Published: July 2016

The orbital comet-asteroid criteria, their premises, dynamical reasoning, and ranges of applicability are reviewed. Mapping of all known comets and asteroids in a plane of energy intergral in the two body problem (1/a) vs. that in the restricted three-body problem (Tisserand invariant) is presented. The potential evolutionary paths from different sources of active comets into short-period orbits are delineated and interfaced with the process of reducing the perihelion distances of the asteroids. The significance of resonances with Jupiter is emphasized. Statistics of observed close approaches of individual comets and asteroids to the Earth is analyzed to estimate their relative fluxes. Active cometary nuclei are found to represent about 1/8 of the flux of objects with radii exceeding 1 km in the vicinity of the Earth, and their contribution tends to diminish significantly for still smaller bodies. However, there is no evidence against comets leaving inactive asteroid-like nuclei with considerable lifetimes which may represent a significant, though secondary, source of meteors and even meteor streams. An overwhelming majority of the Apollo and Amor objects are suggested to be of asteroidal nature; the most probable exceptions are selected and recommended for detailed observation.
9. Some Interrelations of Asteroids, Trojans and Satellites
Authors: Gehrels T.
Published: July 2016

The Trojans of Jupiter have the same magnitude-frequency distribution as the asteroids, but there is a puzzling asymmetry of the densities in Preceding and Following Lagrangian points. The outer satellites of Jupiter have a peculiar magnitude-frequency distribution, with large and also small ones missing; they therefore cannot be captured asteroids or Trojans unless during the capture a resisting medium was present out to ˜400 RJ for proto-Jupiter.
9. Relationship between the Composition of Solid Solar-System Matter and Distance from the Sun
Authors: Wasson J. T.
Published: July 2016

The chondritic meteorites have “solar” compositions, indicating that they have avoided fractionation in planetary processes such as partial melting or fractional crystallization. Since chondrites contain solar proportions of volatiles having nebular condensation temperatures ≤500 K, it follows that agglomeration of grains and accretion to parent bodies occurred after the nebula had cooled to such low temperatures, and, that models calling for simultaneous condensation and accretion of high-temperature minerals such as Fe-Ni metal or ferromagnesian silicates are implausible.

Two independent intergroup fractionations have been recognized in chondritic materials; refractory element abundances (e.g., the Ca/Si ratio) and degree of oxidation measured by the FeO/(FeO + MgO) ratio decrease through the chondrite sequence: carbonaceous-ordinary-IAB-E. Hiatus between groups result from incomplete sampling by the Earth of the original spectrum. A plausible speculation is that this sequence reflects formation at different nebular pressures and temperatures, the fine-grained, oxidized, volatile-rich carbonaceous chondrites forming at lower temperatures >5 AU from the Sun, and the reduced enstatite chrondrites forming at higher temperatures near the Sun. The high fall frequency of the three groups of ordinary chondrites suggests an origin in the asteroid belt. The degree of oxidation of the IAB chondrites appears to be slightly lower than that of the Earth, suggesting an origin near or slightly less than 1 AU from the Sun. The O-isotope compositions of chondrites are consistent with this picture.

Asteroids tend to be light or dark, with a hiatus in properties between these two classes. This can be understood if the light materials are ordinary chondrites originally formed at 2.2-3.5 AU, whereas the dark materials originated at >5 AU, and were deposited in the asteroid belt during a later period as a result of a major increase in the influx of cometary materials through the inner sc1ar system associated with the generation of the Oort cloud of comets.
A Thermal Pressure Inside the Local Bubble, as Revealed by CI Fine-Structure Excitation
Authors: Jenkins Edward B.
Published: July 2016

Ultraviolet absorption lines from carbon atoms within a neutral cloud inside or near the edge of the Local Bubble can reveal the thermal pressure of the gas, since the relative populations of the fine-structure levels are determined by a balance between collisional excitation and radiative decay. Features from a C I multiplet appearing in the uv spectrum of the starδCyg (l= 79°,b= +10°,d= 52 pc) were observed with the echelle spectrograph of the Goddard High Resolution Spectrograph on HST. An interpretation of absorptions detected from the two lowest levels gives a thermal pressure range 102.7<p/k< 103.7cm−3K.
Structure Within the Local Bubble: Properties of Individual Clouds
Authors: Beckman J.E. , Trapero J. , Álamo J.R. , Génova R. , Lundstrom I.
Published: July 2016

Starting from the casual observation that neighbouring lines of sight to stars at similar distances in the LISM show abruptly varying column densities, we developed a technique for measuring properties of single clouds. Fig.l shows an idealized version of this. The steps (Trapero et al. 1992, 1995) are:

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Correct for extinction the distances to local stars used, via B-V (where available), or our own measured Nal or KI absorptions.

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Measure diametral column density towards A from Nal or KI equivalent width and convert to hydrogen: N(H) [cm−2].

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Measure cloud diameter, between E and E’.

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Estimate the number density, n(H) = N(H)/d [cm−3].

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Use a canonical thermal pressure, nT = 3500 K cmThis at least gives the decision cool (<100K) or warm (>5000K).

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Estimate the cloud mass by integrating n(H) over the estimated volume.

Following up, cool cores within warm clouds, or warm envelopes around cool clouds can be identified using distance and velocity as tags. We have found empirical rules of thumb to guide us:

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The KI resonance at 7699Å is ideal for finding cool clouds; it is too weak to show up in warm clouds.

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NaI D doublet lines weaker than 5mÅ typify warm clouds. There are too many of these, by a factor 50, to come from cool cloud edges. This is confirmed by the “low velocity Routly-Spitzer effect” (see below).
Remarkable Details in the Local Bubble’s HI Distribution
Authors: Bystrova Natalija V.
Published: July 2016

We discuss details in the galactic HI distribution, which are relevant for studies of the Local Bubble. All results are based on the 21 cm Sky survey with the Large Pulkovo Radiotelescope. The antenna temperature scans were decomposed in two components and after the subtraction of the broad one two details in the residual are presented in this paper. The first is an estimate of the distance to the Sancisi-van Woerden filament in the Sco-Oph region. The second is the connection of a 21 cm feature in the southern galactic quadrant II with the negative-velocity elliptical brightness distribution around the South Pole of the Galaxy.
Bubbles in Collision: Hydrodynamical Models
Authors: Chernin A.D.
Published: July 2016

Computer simulations and laboratory experiments with shock waves are suggested for the study of collisions of bubbles or superbubbles. They describe how the colliding bubbles merge with the formation of an expanding common shell and a complex internal dynamical structure which includes two vortex tori and collimated outflows.
Evolution of Evolution of Superbubbles
Authors: Ikeuchi Satoru
Published: July 2016

In the first place, I will summarize the evolution of our picture of the ISM over the past several decades in order to see the importance of superbubbles for ISM structure. In accordance with the progress of observations, the picture of the ISM has dramatically changed from the 1960s. Then, I will review the evolution of theoretical models of superbubbles including the idea of chimney structures of the ISM.
Origin and Evolution of the Cepheus Bubble
Authors: Patel N.A. , Goldsmith P.F. , Heyer M.H. , Snell R. , Pratap P.
Published: July 2016

The Cepheus bubble is a giant shell with a diameter of about 120pc, discovered by Kun (1987) from IRAS sky flux maps. We have imaged this 10° × 10° region in the CO J=l-0 line, using the FCRAO Quarry system with sample spacing equal to the 45” FWHM beam width. We estimate the total molecular gas mass to be ~ 105 solar masses and a total kinetic energy ~ 1051 ergs. We find 49 O and B0-B2 type stars in the Cepheus bubble region, most belong to the CepOB2 association. 120 IRAS point sources, selected according to color criteria representative of young stellar objects, fall within our map. Many of these sources are associated with the globules and filamentary structures seen in the CO emission, similar to the situation found in IC1396 (Patel et al. 1995). These stars, which are still associated with dense molecular gas plausibly represent the third and youngest generation of stars in this region.
The ORFEUS Far Ultraviolet Spectrum of the LMC Binary Star HDE 269546
Authors: Widmann H. , Krämer G. , Appenzeller I. , Barnstedt J. , Fromm A. , Gölz M. , Grewing M. , Gringel W. , Haas C. , Hopfensitz W. , Kappelmann N. , Krautter J. , Lindenberger A. , Mandel H.
Published: July 2016

Far UV high resolution spectra of 3 LMC and SMC stars were obtained with the Echelle spectrograph during the second ORFEUS mission in Dec. 1996. We present the first results from observations of the LMC star HDE 269546. We find definitely components of very hot gas identified as OVI and SVI absorption in the galactic halo of the Milky Way and in the LMC. Additionally, more than 30 ions of the most abundant elements in different stages of ionization can be identified in both our galaxy and the LMC. For the first time we can identify a significant absorption component of molecular hydrogen in the ORFEUS II Echelle spectrum with a redshift of 200 km s−1, doubtlessly to be attributed to the LMC.
ROSAT Observations of NGC 4258
Authors: Vogler Andreas , Pietsch Wolfgang
Published: July 2016

We performed deep follow up observations of the active spiral galaxy NGC 4258 with the ROSAT HRI and PSPC to study the different emission components. The overall luminosity of NGC 4258 is Lx ~ 2 × 1040 erg s−1 in the 0.1 – 2.4 keV ROSAT band. Besides a weak nuclear point source (Lx ≲ 1038 erg s−1) fourteen point sources are detected in the NGC 4258 disk (integral Lx ~ 3 × 1039 erg s− 1). The bulk of the X-ray emission is not resolved. The main contributions are explained by hot interstellar medium along the anomalous spiral arms of NGC 4258 (Lx ~ 1 × 1040, T ~ 0.4 keV) and by interstellar medium escaping from NGC 4258 disk into the approaching halo hemisphere (Lx ~ 4 × 1039 erg s−1, T ~ 0.2 keV)

Surface brightness, temperature and absorption profiles have been taken for the X-rays in the regions of the anomalous arms. The highest and lowest absorption was received for the NW and SE tips of the arms, respectively. Our X-ray findings are compared to a model of the anomalous arms which suggests that the bar of the galaxy causes shocks in the interstellar medium and might heat a small part of it to X-ray temperatures.
Rotationally Modulated Winds of O Stars
Authors: Fullerton Alex W.
Published: July 2016

The stellar wind diagnostics of some well-studied O stars exhibit cyclical variations with periods that are probably related to the rotational period of the underlying star. This rotational modulation is usually attributed to large scale, persistent structures in the wind, which are thought to be generated and maintained by photospheric processes that alter the emergence of the wind from different regions of the stellar surface. In this review, three case studies are used to illustrate the patterns of variability that are attributed to rotational modulation and to highlight some open issues connected with this hypothesis. The problems associated with establishing the occurrence of rotational modulation rigorously are also discussed.
Short and Medium Term Variability of Emission Lines in Selected Southern be Stars
Authors: Rivinius Thomas
Published: July 2016

We observed a sample of several southern Be stars from 1995 to 1997 typically for several months in each season using our spectrograph HEROS. One of these stars, μ Cen, was found to be in the process of continued gradual recovery of the Hydrogen emitting disk which had been lost from 1977-1989. During the monitoring period numerous line emission outbursts were observed. A generalized pattern of an outburst cycle is derived from observations of different circumstellar lines at times of various levels of emission from the disk. Relative quiescence in which mostly periodic varaibiltiy is seen, rapid decreases of emission (precursor), outburst, and subsequent relaxation can be distinguished as the main constituing phases, even though there are distinct differences between different groups of spectral lines. Based on this empirical phenomenology, a schematic picture of the associated ejection of matter into a near-stellar orbit is sketched and similarities between μ Cen and other stars will be outlined.
Non-isotropic Outflows in the Infrared: ISO Imaging of LBVs
Authors: Trams Norman R. , van Tuyll C.I. , Voors Robert H.M. , de Koter Alex , Waters Laurens B.F.M. , Morris Patrick W.
Published: July 2016

In this review we present the ISO imaging of nebulae around Luminous Blue Variables. Three LBVs have been imaged with ISO: HR Car, AG Car and the LBV candidate G79.29+0.46. The ISOCAM instrument did not resolve the nebula around HR Car. However some nebular emission lines are seen in the spectral energy distribution of this source. A proper deconvolution of the images may resolve the nebula. For AG Car and G79.29+0.46 the nebula is clearly resolved. The structure and intensity distribution of the nebular emission is dependent on the wavelength, indicating a separation between the ionised matter and the dust in the nebulae. Some model calculations are presented for the G79.29+0.46 nebula.
Long-Term Behaviour of the Variable Wind of P Cygni
Authors: Kolka Indrek
Published: July 2016

P Cygni has been for a long time an often-used target of observations, and a test object to prove several modelling approaches (cf. e.g. Najarro et al. 1997, and references therein). However, the origin of it’s stable variability pattern with moderate amplitudes is poorly known yet. In this contribution I will concentrate on the spectroscopic variability. A more elaborated version of this paper considering many kinds of variability data on P Cygni will be published elsewhere (Kolka 1998).

The striking phenomenon in the spectra of P Cygni is the cyclic drift of subsequent individual components through the absorption part of the P Cyg-type profile. This is demonstrated in Fig.1a in the case of three Balmer lines in 1982 (the data adopted from Markova, Kolka 1989). Every new drift-cycle starts when the component with smaller Doppler-shift becomes deeper than it’s neighbour.