bluuebunny/crossref_metadata_2025 huggingface dataset:
A Model-Atmosphere Analysis of the Spectrum of Arcturus
Authors: Mäckle R. , Holweger H. , Griffin R. and R.
Published: July 2016

We have analysed the spectrum of Arcturus (K2 III) relatively to the Sun, using a differential technique employing empirical models for both stars. We derive an effective temperature of 4260 ± 50K and a surface gravity log g = +0.90 ±0.35; these in turn lead to a very low mass, in the range 0.1 to 0.6 M⊙. Elements are found to be underabundant by an average factor of 4 compared with the Sun. The abundance patterns in the two stars are significantly different, in keeping with the belief that Arcturus is a star of an older generation than the Sun. The carbon isotope ratio, which is as small as 5 or 6, shows that the atmospheric material of Arcturus has been processed through the CNO cycle, and theoretical arguments also indicate that Arcturus is somewhat evolved.
SOME COMMENTS ON A CATALOGUE OF ATMOSPHERIC PARAMETERS AND [Fe/H] DETERMINATIONS
Authors: de Strobel G. Cayrel
Published: July 2016

A few examples are given showing the utility of the catalogue of iron/hydrogen determinations for astrophysical researches. These are:

(a)

Histograms of dwarfs and giants analyzed in detail with spectral type between O and M.

(b)

Logarithmic abundances diagrams of given stars.

(c)

The impact on spectral classification of high-dispersion-detailed-analysis results.

(d)

The use of well-determined chemical and physical parameters of nearby stars for the construction of HR diagrams in the (Mbol –log Teff) plane.

The spectra of F, G and K stars having the iron lines at their best visibility, special emphasis has been given to the results concerning these stars.
Narrow-Band Photometry of a and F Stars
Authors: Mendoza E. E. V.
Published: July 2016

The α and λ photometric systems are used to obtain a bi-dimensional representation of the A and F stars.
The Bonner Spectral Atlas and Three-Dimensional Classification at Low Dispersions
Authors: Seitter W. C.
Published: July 2016

Work on the third part of the Bonner Spectral Atlas: Peculiar Stars has well progressed during the past year. Observations of the more than 200 stars – photographed with a dispersion of 240 Å mm−1 at Hγ on I-N plates – is nearing completion.

The arrangement of the spectra will be as follows:

1.

WR-stars

2.

O-stars Of sequence

3.

Peculiar B-type stars emission-line objects

4.

Ap-stars with various sequences: Cr-Mn-Hg-rare earths

5.

Asi-stars

6.

Am-stars

7.

Late-type peculiar stars Ba II, CH

8.

C-stars

9.

Late M-type stars

10.

S-stars

11.

Composite spectra

12.

Spectra with large rotational broadening

The 12 groups are displayed on 40 plates, each with 6–8 objects. Stars of groups 8 to 10 will be presented with different exposures in order to facilitate the discovery of faint objects.

Sample plates will be shown and discussed.
Nitrogen and Carbon Anomalies in OB Spectra
Authors: Walborn N. R.
Published: July 2016

The following new OBN and OBC stars have been found: HD 75860, BC 2 Iab; HD 104565, OC 9.7 Ia; HD 123008, ON 9.7 Iab; and HD 150574, ON 9 III(n). Examples of morphologically more moderate CNO anomalies in OB spectra are also discussed; it is concluded that the O9-B0 7 supergiants of the Orion Belt and NGC 6231 (the nuclear cluster of Scorpius OB1) are systematically nitrogen-deficient. One possible explanation of these nitrogen-deficient supergiants in sub-associations is that they may have formed from nitrogen-deficient clouds; another could be that the more numerous morphologically normal supergiants show the effects of mixing in their spectra, while the nitrogen-deficient ones are relatively younger or have not yet been red supergiants. No red supergiants are found in Sco OB1, whereas NGC 3293 contains two B0 supergiants with normal CNO spectra together with a red supergiant. The paper will appear in the Astrophysical Journal, April 15, 1976.
A Population Discriminant in M-Dwarf Spectra
Authors: Bidelman W. P. , Smethells W. G.
Published: July 2016

The CaH bands in the λ 6385 region of the spectra of M dwarfs have long been known; they become visible in the late K's and show a gradual increase in strength to later types. However, Greenstein and Eggen have noted that there is a substantial strengthening of all the hydride bands, including CaH, in high-velocity dwarfs (notably G95-59), and one of us (W.P.B.) has also seen this effect in suitable Warner and Swasey Observatory objective-prism plates of the rather low-velocity subdwarfs Ross 730 and 731. In a recent southern-hemisphere survey with the Curtiss Schmidt, Smethells has discovered nearly 200 late K and early M dwarfs, for all of which estimates of CaH-band strength were made. He found a considerable variation of the CaH-band strength in stars of the same (TiO-band) spectral type, and a slight tendency for the CaH/TiO band ratio to increase with increasing tangential velocity. A fuller account of this work will appear elsewhere.
Cometary volatiles
Authors: Bockelee-Morvan D.
Published: July 2016

Comets are believed to be the most pristine material surviving from the origin of the Solar System. The nature of their volatiles should in principle provide chemical and physical clues to their formation environment in the solar nebula. Another important aspect of the study of comets is the extent to which they may incorporate relatively unprocessed interstellar material.

Our knowledge of the composition of cometary ices has been greatly improved in this last decade. The years 1995-1996 were rich in new results, with the close approach to Earth of comet C/1996 B2 Hyakutake and the discovery of the bright comet C/1995 O1 Hale-Bopp at large heliocentric distance. We will present the current knowledge of the nature and abundances of cometary volatiles and mention some of the outstanding issues related to the origin of comets and their links to interstellar material.
Electronic spectra of carbon chains of relevance to astrophysics
Authors: Maier John P.
Published: July 2016

The electronic absorption spectra of a variety of carbon chains have been identified in the laboratory. The measurements were carried out in 5 K neon matrices on mass-selected species. On the basis of the trends evident in the homologous series, it can be predicted in which region absorption bands of the carbon chains are to be expected for the not yet measured longer and isoelectronic species. The spectroscopic characteristics, photostability and structural considerations point out which and what size carbon chains could be the diffuse interstellar bands absorbers.
Determination of opacity data bases for TiO and H2O
Authors: Langhoff S.R. , Schwenke D.W. , Partridge H.
Published: July 2016

Current ab initio methods for determining potential energy surfaces are discussed in relation to the TiO and H2O molecules, both of which make important contributions to the opacity of M-type stars. For the TiO molecule we discuss the determination of the radiative lifetimes of the excited states and band oscillator strengths for both the triplet and singlet band systems. While the theoretical radiative lifetimes for TiO agree well with recent measurements, the band oscillator strengths differ significantly from those currently employed in opacity calculations. For the H2O molecule we discuss the current results for the ground state potential energy and dipole moment surfaces generated at NASA Ames. We show that it is necessary to account for such effects as core-valence correlation to generate a potential energy surface of near spectroscopic accuracy. The current status of our effort to establish opacity data bases for both TiO and H2O is described.
Quasar absorption line observations
Authors: Bechtold Jill
Published: July 2016

Searches for molecular gas in high redshift quasar absorption-line galaxies are reviewed. Despite a great deal of effort, firm evidence has been found in only a few, atypical cases — in clouds which are very close to a luminous quasar, or in objects which have been magnified by gravitational lensing. Recent observations suggest that normal galaxies at z ∼ 3 had star-formation rates about ten times that of the present-day Milky Way. Hence, detections of molecular gas by means of the millimeter transitions of CO will require more sensitive observations than have been attempted to date.
The Physics of Flare Stars
Authors: Evans David S.
Published: July 2016

This paper reports the researches of the Texas flare star group. High time resolution and simultaneous photometric, spectroscopic and, if possible, radio observations of flaring stars are essential. Fast and slow flares are distinguished and their distinct optical, spectroscopic, and probably, radio effects are noted. The starspot model satisfactorily accounts for many optical and spectroscopic flare star properties, including the precursor phenomenon and quasi periodicity of flaring found by some observers. The basic mechanism of flares is thought to be magnetic field collapse on a scale vastly greater than in the Sun, but further observations are essential, even though there are theoretical grounds for support. No analogue of the solar cycle has yet been detected. The problem of duplicity remains a puzzle.
On the Nature of Maser Sources in Infrared Stars
Authors: Burdjuzha V. V. , Ruzmaikina T. V.
Published: July 2016

Supergiant infrared stars with OH maser emissions, like NML Cyg, VY CMa, and VX Sgr, are discussed assuming a model consisting of a star with a photospheric temperature of about 2000 K and a radius of R ∼ 2 × 1014 cm surrounded by a gas and dust shell. A possible similarity with OH Miras is mentioned.
Some Remarks on the Absolute Magnitudes of Cepheids
Authors: Opolski A.
Published: July 2016

This paper contains a rediscussion of the period-luminosity relation of type I-cepheids. Special attention is paid to the radius and its variation.
S Dor-Type Variables in Other Galaxies
Authors: Sharov A. S.
Published: July 2016

The variability of these objects, almost the brightest ones found in galaxies, is discussed, followed by a description of colour indices and spectra. In the last sections the classification problems and items for further investigation are mentioned.
Observations of Radially Expanding Stratified Atmospheres of Wolf-Rayet Stars
Authors: Seggewiss W.
Published: July 2016

A correlation between lower excitation potential and radial velocity of violet-displaced absorption components in the spectra of Wolf-Rayet stars is established. The relationship supports the concept of a radially expanding stratified atmosphere in which the expansion velocity increases outwards. The outermost layers of the atmosphere of one star (HD 151932, WN7) display oscillations with a periodicity of about 3.5 days.
Variations of the C III 5696 Å Emission Line in Wolf-Rayet Stars
Authors: Schumann J. D. , Seggewiss W.
Published: July 2016

Slow and rapid fluctuations of emission and absorption features of the C III emission line at λ 5696 Å in WC stars are described. They might be attributed to moving clouds in the expanding stellar envelope.
X-Ray Nova Flares
Authors: Amnuel P. R. , Guseinov O. H.
Published: July 2016

In order to find out the physical nature of galactic X-ray sources, data on the variability of 24 sources during 1964–1971 have been investigated. The fluxes of 9 sources are found to be increasing to the maximum value (for several months) and then slowly decreasing (for 3 years). These 9 sources have been related by us to the class of X-ray Novae. The X-ray Nova synthetic light curve has been drawn from data of the fluxes of 9 discovered Novae. Assumptions have been made on the physical nature of the X-ray Novae. Between the flares the X-ray Novae may be weak X-ray sources with a luminosity of about 1034 erg s−1. During the flares the luminosity increases to about 1038 erg s−1. The number of X-ray sources in the Galaxy is about 103–104. The object of the optical identification may be a dwarf star of no earlier spectral class than F.
Optical Variability of the N Galaxy 3C 371
Authors: Babadzanjanz M. K. , Belokon' E. T.
Published: July 2016

On the basis of a uniform series of photographic observations a 163 day period for the light variations of the N galaxy 3C 371 is found. The similarity of the form of the light curve for the different components of the light variations with the different time scales is noted. The form of the light variations was observed to be identical to that of the quasars 3C 345 and 3C 454.3.
New Observational Data Concerning 4 Her and ζ Tau
Authors: Harmanec Petr , Koubský Pavel , Krpata Jiří , ŽĎárský František
Published: July 2016

Rectified intensity profiles of the Hα and Hβ Balmer lines of the shell star 4 Her were studied on 86 coudé spectrograms taken during 1969–1974. The central intensities of both lines vary periodically with the period of velocity changes equal to 46.194 days, reaching two maxima and minima each cycle. Radial-velocity curves of individual Balmer lines differ systematically one from another, the amplitude of the Hα variations being largest. The V/R ratio of the Hα emission peaks varies in phase with the velocity changes. The velocity of the Hα emission is found to be almost invariable. A model is suggested to explain the observed variations in which 4 Her is considered to be an interacting binary. The full paper will appear in Bull. Astron. Inst. Czech.27, No. 1 in 1976.

Radial velocities of high-dispersion spectrograms of ζ Tau, obtained mostly during the last observing season, indicate the following facts: (1) Several distinct velocity systems are present in the Balmer lines, not a continuous progression. (2) The main absorption component of the Hα line does not share the long-term velocity variations, its velocity being always rather close to the systemic velocity + 22 km s−1. (3) The pseudoperiod of the long-term velocity variations has changed and is probably decreasing.
A Comparative Study of the Shell of ζ Tau and 48 Lib
Authors: Delplace A. M. , Chambon M. Th.
Published: July 2016

Two unstable shell stars, ζ Tau and 48 Lib, are compared. In the Herman-Rojas (1974) and Rountree-Lesh (1968) classifications, both stars have luminosity class III. These stars show similar features in the variation of the intensities, the profiles, and the radial velocities of the shell lines. An attempt has been made to explain the evolution of these unstable features.
A Model for the Shell of HD 50138
Authors: Houziaux Léo , Andrillat Yvette
Published: July 2016

A model for the shell star HD 50138 is inferred from the observation of the continuous spectrum from 0.14 to 10 μ.
Radio Observations of Be Stars: (Review Paper)
Authors: Purton C. R.
Published: July 2016

During the past few years the search for radio stars has been both intensive and extensive, and Be stars are among the various types of objects which have been examined. A large number of Be stars have not been detected, and to date no classical Be star has been found to emit detectable amounts of radio emission. However, following the tradition of radio astronomy to emphasise the abnormal or extreme cases, radio emission has been observed which is associated with a few peculiar Be stars.
The Complex Structure of the Ca II H and K Lines in the Spectrum of the A0ep Star with Infrared Excess HD 190073
Authors: Surdej J. , Swings J. P.
Published: July 2016

Radial velocities and profiles of the components of the H and K lines in the spectrum of HD 190073 are analyzed in a 24-spectrum sample covering the period 1943–74. A 2-to-1 ratio in the radial velocities of some components is shown not to be significant on a spectrum-to-spectrum basis, contrary to suggestions by Merrill (1951) and Scargle (1973). The details of the H and K complex structure are correlated with the profiles of the Balmer lines. Radiative forces acting selectively via a resonance scattering mechanism of Ca+ atoms are capable of producing the main features of the complex profiles of H and K in HD 190073 and in other stars exhibiting similarities to HD 190073 (such as P Cygni Balmer lines and infrared excess).
Theoretical Emission-Line Profiles Computed at Ondřejov
Authors: Kříž Svatopluk
Published: July 2016

A rotationally symmetrical disk-shaped envelope was considered and the steady-state equations for level populations solved using the escape probability approximation. The line profiles were then calculated and compared with observations.
Duplicity of Be Stars as Seen from Ondřejov: (Review Paper)
Authors: Harmanec Petr , Kříž Svatopluk
Published: July 2016

Observed Be stars are considered to be interacting binaries undergoing mostly case B mass exchange. Their observed properties can be explained satisfactorily as the consequences of different modes of mass transfer. Suggestions for further observational and theoretical studies to verify or to disprove the hypothesis presented here are briefly outlined.
On the Detection of Binary Be Stars
Authors: Polidan R. S.
Published: July 2016

Possible methods for detecting the presence of a cool companion to a Be star are discussed. Photometric observations are shown to be incapable of detecting companions in all but the most extreme cases. Spectroscopic investigation is also unlikely to yield many new discoveries. It, however, remains the most promising method for the detection of binary Be stars. The four known binary Be stars are also discussed.

Infrared calcium triplet emission in Be stars is discussed in detail. The lines are shown to originate in a region of large optical thickness and low temperature (T ~ 5000 K). The possible connection between the presence of calcium triplet emission and binary nature is briefly discussed.
Evidence for the Existence of Mass-Exchange Binary Be Stars from Periodic Spectral Variations
Authors: Peters Geraldine J.
Published: July 2016

In this paper, we discuss the Be stars which show recurrent shell structure and/or cyclic variations in the profiles of their emission lines with periods near 100d and, thus, are good candidates for interacting binaries undergoing mass-exchange. The periodic spectral variations observed in the Ble star HR 2142 are reviewed and brought up to date in the light of recent observations. HR 2142 is then compared with other periodic binary Be stars (AX Mon, 17 Lep, HD 218393, HD 173219, and φ Per) in order to point out the wide variance in observed spectra which interacting binaries can display.
The Cause of the Nova Outburst
Authors: Starrfield S. , Sparks W. M. , Truran J. W.
Published: July 2016

We have evolved a large number of models of thermonuclear runaways in the hydrogen-rich envelopes of 1.00 M⊙ carbon-oxygen white dwarfs. Models characterized by enhanced CNO abundances satisfy the observations of the common nova outburst. They eject from 1027 to 1029 g moving with velocities of 200–2400 km s−1: kinetic energies of 1044 to 1045 erg. The theoretical light curves are similar to the observed light curves of common novae during the early stages of the outburst. As a consequence of our studies, we can present an explanation for the continuous ejection of mass which is observed for long times after the initial outburst and for the relationship between maximum magnitude and the decline to minimum. We are also now able to present an explanation for the constant luminosity phase of the outburst and the oval shapes of the ejected nebulae.

We have extended our earlier work to models with extreme enhancements of 12C and to models which include the infalling material in the evolution. The extreme 12C studies result in outbursts which reach near supernova proportions while the accretion models result in light curves which resemble observed light curves quite closely. Finally, the accretion studies also demonstrate the need for enhanced abundances.
Masses and Evolution of Cataclysmic Binaries
Authors: Ritter H.
Published: July 2016

The determination of masses and mass ratios of cataclysmic binaries is discussed. It is suggested that these systems started as wide binaries, which have lost substantial amounts of mass and still more substantial amounts of angular momentum.
Accretion Processes in Close Binaries
Authors: Rees M. J.
Published: July 2016

Accretion processes and the associated emission mechanisms are discussed, with special reference to binary X-ray sources.
Numerical Simulation of Mass Transfer and Accretion Disc Flow in Binary Systems
Authors: Lin D. N. C. , Pringle J. E.
Published: July 2016

A numerical simulation of equilibrium gas flow in a binary system is presented for the case in which an accretion disc forms around the accreting star (primary). Preliminary results are shown for the mass ratios 0.4, 1.0 and 2.5. Two main conclusions are reached. First, the accretion disc is quite well defined and is comparable in size to the Roche lobe of the primary. Second, all but a few per cent of the mass transferred is accreted by the primary.
Mass Transfer in Semi-Detached Binaries
Authors: Shu F. H.
Published: July 2016

The dynamics of gas streams in semi-detached binaries is reviewed from the standpoint of the theory of matched asymptotic expansions. Physical concepts are emphasized, and some astronomical applications are considered. The model of impact-driven accretion disks is also discussed briefly.
Notes on the Interpretation of Observations of Circumstellar Matter in Binary Systems
Authors: Batten A. H.
Published: July 2016

Problems of relating different observational indications of the presence of circumstellar matter in binary systems are discussed, with especial reference to the observed period changes in systems whose other properties are very similar. It is suggested that some fluctuations observed in the periods of close binary systems are apparent and not to be attributed to dynamical causes. The discussion includes some account of recent activity in U Cep, and the possible causes of spectroscopic changes in binary systems are examined.
Identification of 3He in the Binary System 68u Her
Authors: Hilditch R. W. , Hill P. W.
Published: July 2016

From a radial velocity study of 60 spectrograms of the binary system 68u Her, systematic velocity differences have been found to exist between the He I singlet lines and the He I triplet lines of the primary component. These differences are independent of orbital phase, date of observation or spectrograph employed and can be interpreted in terms of the existence of a large fraction of 3He in the atmosphere of the primary component. A 3He/4He ratio of between 4:1 and 49:1 is suggested.
Progress in Contact-Binary Energy Transfer
Authors: Whelan J. A. J.
Published: July 2016

The energy transfer problem in contact binaries is briefly reviewed.
Evolution of Contact Systems
Authors: Vilhu O. , Rahunen T.
Published: July 2016

The evolution of contact binaries with common convective envelopes has been studied. Gravitational energy due to the mass exchange is taken into account in both stars, which turned out to be of crucial importance. Three qualitatively different evolutionary tracks have been found for an initial system 1.2M⊙ + 1.0M⊙. One of these corresponds to those found by Moss (1971), in which mass transfers, on a long time scale (≈5 × 108 yr), from the less massive component to the heavier. The second is similar to the solution found by Hazlehurst and Meyer-Hofmeister (1973), in which the evolution proceeds towards equal masses in a much shorter time scale (≈2 × 107 yr). The third possibility is similar to the first one, but its time scale is 10 times shorter (≈5 × 107 yr). The true evolutionary track may well oscillate randomly around the different solutions (rapid period changes).
Rotational Angular Momenta of Close Binary System Components
Authors: Ureche V.
Published: July 2016

The ratio between rotational angular momentum, Jrot, and orbital angular momentum, Jorb, in close binary systems and its variation with mass ratio is studied. The tables and the graphs give this variation for detached systems, contact systems, semidetached systems and for systems containing a supernova-remnant component and a contact component. For this study some statistical relations of close binary stars were used.

The ratio Jrot/Jorb is sensitive to the variation of the mass ratio q. If q differs much from unity and if the concentration of the stellar matter is moderate (polytropic index n ~ 3), the neglect of rotational angular momentum, Jrot, is not justified.
The Origin of the RS CVn Binaries
Authors: Biermann P. , Hall D. S.
Published: July 2016

We consider six possible origins for the RS CVn binaries based on the following possibilities. RS CVn binaries might now be either pre-main-sequence or post-main-sequence. A pre-main-sequence binary might not always have been a binary but might have resulted from fission of a rapidly rotating single pre-main-sequence star. The main-sequence counterparts might be either single stars or binaries.

To decide which of the six origins is possible, we consider the following observed data for the RS CVn binaries: total mass, total angular momentum, lack of observed connection with regions of star formation, large space density, kinematical age, and the visual companion of WW Dra. In addition we consider lifetimes and space densities of single stars and other types of binaries.

The only origin possible is that the RS CVn binaries are in a thermal phase following fission of a main-sequence single star. In this explanation the single star had a rapidly rotating core which became unstable due to the core contraction which made it begin to evolve off the main sequence. The present Be stars might be examples of such parent single stars.
Concluding Remarks
Authors: Plavec M.
Published: July 2016

This has been a very good meeting. If you cannot read some or all of the papers in full, read at least these remarks. It is an attempt to summarize the highlights, naturally an attempt too imperfect, biased, and highly subjective.
Stability of the Solar System
Authors: Szebehely Victor
Published: July 2016

This paper reviews the present status of research on the problem of stability of satellite and planetary systems in general. In addition new results concerning the stability of the solar system are described. Hill's method is generalized and related to bifurcation (or catastrophe) theory. The general and the restricted problems of three bodies are used as dynamical models. A quantitative measure of stability is introduced by establishing the differences between the actual behavior of the dynamical system as given today and its critical state. The marginal stability of the lunar orbit is discussed as well as the behavior of the Sun-Jupiter-Saturn system. Numerical values representing the measure of stability of several components of the solar system are given, indicating in the majority of cases bounded behavior.
Stability of Periodic Planetary-Type Orbits of the General Planar N-Body Problem
Authors: Hadjidemetriou John D.
Published: July 2016

It is known that families of periodic orbits in the general N-body problem (N≥3) exist, in a rotating frame of reference (Hadjidemetriou 1975, 1977). A special case of the above families of periodic orbits are the periodic orbits of the planetary type. In this latter case only one body, which we shall call sun, is the more massive one and the rest N-1 bodies, which we shall call planets, have small but not negligible masses. The aim of this paper is to study the properties of the families of periodic planetary-type orbits, with particular attention to stability. To make the presentation clearer, we shall start first with the case N=3 and we shall extend the results to N>3. We shall discuss planar orbits only.
Periodic Orbits of Arbitrary Inclinations and Eccentricities in the General 3-Body Problem
Authors: Marchal C.
Published: July 2016

Usual periodic orbits have periods of the order of magnitude of a few revolutions. However if we consider much longer periods it is possible to find, for three given masses, periodic orbits in any neighbourhood of arbitrary given initial eccentricities and inclinations provided that the distance of the outer body is sufficiently large with respect to the mutual distance of the two inner bodies.
Libration of Retrograde Satellite Orbits in the Circular Plane Restricted Three-Body Problem
Authors: Benest Daniel
Published: July 2016

In the circular plane restricted three-body problem, we study the stable large retrograde non-periodic satellite orbits. We use rotating axes with the origin in the body around which turns the satellite, called its primary. We choose the initial conditions such as Yo=0 and Uo=0, so that an orbit can be represented by a point in the (Xo,Vo) plane. In this plane, the set of stable orbits is represented by a limited region, which we call the stability zone. This zone is composed in general by a large continental region, approximately limited by Lagrange points, and a peninsula more or less elongated.
Recent Progress in the Theory of Trojan Asteroids
Authors: Garfinkel Boris
Published: July 2016

In order to provide the necessary background for this report, this section summarizes the previously published “Theory of the Trojan Asteroids, Part I”. Treating the system as the case of 1:1 resonance in the restricted problem of three bodies, the author constructs a formal long-periodic solution of 0(m), where m is the mass-parameter of the system, assumed to be sufficiently small.
A Review of Dynamical Evidence Concerning a Former Asteroidal Planet
Authors: Van Flandern T. C.
Published: July 2016

This paper is a brief review of results presented elsewhere (Van Flandern 1977, 1978). The conclusion of these results is that at least the comets, and probably also the asteroids and meteorites, originated in the breakup of a major planet in the present location of the asteroid belt, at an epoch of just 5×106years ago. Although there are many “well-known facts” about the solar system which seem to contradict this conclusion, these contradictory “facts”, upon closer examination, are often not so convincing as we have been inclined to assume; in each instance so far suggested there is a plausible alternative interpretation of the data which is supportive of the breakup hypothesis. A compelling contradictory argument has not yet surfaced. In view of this, and in consideration of the strength of the arguments favoring the hypothesis, it will be necessary to judge the conclusion on the merits of the case, without the intervention of theaprioridecision that it cannot be true.
On Some Characteristics of the Distribution of Perihelia of Long-Period Comets
Authors: Yabushita S.
Published: July 2016

Although the problem of the origin of comets has not yet been settled, there are only two possibilities; one is to regard that comets formed within the solar system when or soon after planets formed, and the second possibility is that comets have been captured from interstellar space by planetary perturbations or by perturbations of the galactic nucleus. To decide upon the possibility, one has to take into account statistical features of cometary orbits.
The Split Comets: Gravitational Interaction Between the Fragments
Authors: Sekanina Z.
Published: July 2016

The n-body computer program by Schubart and Stumpff (1966) has been slightly modified to study the gravitational interaction between two fragments of a split comet nucleus in the sun's gravitational field. All calculations refer to the orbit of Comet West (1976 VI), the velocity of separation of the fragments is assumed to be equal in magnitude to the velocity of escape from the parent nucleus, and the numerical integration of the relative motion of one fragment (called the companion) with respect to the other (principal fragment) is carried over the period of 200 days from separation.
On the formation of continuous spectrum and emission line profiles of P Cygni
Authors: Nugis T. , Kolka I. , Luud L.
Published: July 2016

The attempts to interpret the values of the observed radio and infrared fluxes of P Cygni via simple mass outflow models (constant outflow velocity or usual radiative acceleration outflow) lead to a strong discrepancy between the observed and the calculated values.
Evidence for non-isotropic mass loss from central stars of some emission nebulae
Authors: Pişmiş Paris
Published: July 2016

In our general program of research on the velocity field of emission nebulae, using the photographic Fabry-Pérot technique, we have included: NGC 6164-5, an H II region with striking symmetry, NGC 2359 a “ring nebula” and Ml-67. The exciting stars in all three are centrally located and are of spectral types 06f (showing P Cygni profiles), WN 5 and WN 8 respectively.
Wolf-Rayet stars in the Magellanic Clouds
Authors: Breysacher J. , Azzopardi M.
Published: July 2016

Up to now 4 WR stars were known in the SMC (Breysacher and Westerlund, 1978) and 76 in the LMC (Fehrenbach et al., 1976). Because no systematic search for WR stars in the SMC had ever been made, a survey was carried out with the ESO Objective Prism Astrograph which resulted in the identification of 4 new WR stars of the WN type, afterwards confirmed by slit spectroscopy. In the LMC, two fields were also observed and 13 new faint WR stars detected. The results presented here mainly concern the SMC WR stars.
Modelling of UV resonance lines
Authors: Lamers Henny J.G.L.M. , Castor John C.
Published: July 2016

The envelopes of early type stars can be studied by comparing observed and theoretical P Cygni profiles of UV resonance lines. The lines are formed by scattering in the expanding envelope and complete frequency redistribution is a reasonable assumption. The Sobolev approximation can be used for the prediction of the profiles, except within a Doppler shift of 2xvthermal from the line center. The profiles are sensitive to the optical depth τrad(v) ∝L ni(r) (dr/dv), but insensitive to the velocity law. We present a fairly simple method to calculate the effects of a photospheric profile or partly overlapping doublets.
The warm wind model
Authors: Lamers Henny J.G.L.M.
Published: July 2016

The analysis of the UV spectra of τ Sco (BO V) and ζ Pup (O4 f) resulted in the empirical warm wind model. In this model the presence of O5+ and N4+ ions in the envelopes of early type stars is explained by collisional ionization in a ‘warm’ envelope of T ≃ 2 105 K.
Stellar corona models
Authors: Hearn A. G. , Vardavas I. M.
Published: July 2016

A new method of calculating models for stellar coronae is being developed with the aim of providing models of coronae around hot stars capable of explaining the observed mass loss as a stellar wind from a hot corona. The method gives a stationary solution to the coupled equations of motion, continuity and energy balance. The equation of motion contains only the gradient of the gas pressure and the acceleration due to gravity. Radiation pressure is not yet included. The continuity equation assumes spherical symmetry. The energy equation includes heating by weak shock waves, heating by the absorption of photospheric radiation through continuous opacity, radiation losses, heating or cooling by conductivity and the effect on the energy balance of the velocity of the expanding atmosphere. The model is assumed to be optically thin. The velocity distribution is calculated from the solution going through the critical point.
Mass flow and evolution of UW Canis Majoris
Authors: Kondo Yoji , McCluskey George E. , Rahe Jürgen
Published: July 2016

The far-UV spectrum of the eclipsing binary UW CMa (O7f + O-B) had earlier been utilized to derive a mass-loss rate of about 10−6 to 10−5 solar mass per year. The mass flow seems to be basically in the form of a stellar wind emanating from the O7f primary component, with radiation pressure as the controlling factor. The main characteristics that make UW CMa a possible progenitor of a Wolf-Rayet system are discussed.
Results from the 1977 coordinated observing campaign on HDE 226868 = Cygnus X-1
Authors: Bolton C. T.
Published: July 2016

A coordinated campaign of radio, optical, and x-ray observations of the bright x-ray source Cygnus X-1 took place August 7–21, 1977 under sponsorship of Commission 42 of the International Astronomical Union. Radio flux measurements, optical spectra, photometry, and polarimetry were obtained during this period by ten groups from Canada, Great Britain, the Soviet Union, and the United States. The x-ray flux was monitored continuously by the SAS-3 satellite between August 11.0 and 17.0.
Theoretical evolution of massive stars with mass loss by stellar wind.
Authors: Chiosi C. , Nasi E. , Bertelli G.
Published: July 2016

Although it was known since a long time that very luminous blue and red stars may show evidence of mass outflow, it was the advent of the Copernicus satellite that clearly ascertained all OB supergiants (and also the most luminous main sequence stars) are losing mass at rates that are significant for their evolutionary history. The observational information for blue luminous stars (O, Of and WR) has been recently reviewed by Conti (1978), who discussed in some detail the data available for different spectral regions. The rates of mass loss inferred from these observations are estimated to be in the range 10−7to 10−5M⊙/yr for OB stars, and from 10−5to 10−4M⊙/yr for WR stars. Several theoretical models have been proposed to explain those high mass-loss rates, and the high terminal velocities ranging from 1000 to 3000 km/sec. The two basic models are: the cool radiation pressure model, originally proposed by Lucy and Solomon (1970) and elaborated by Castor et al. (1975), in which the envelope is accelerated by momentum transfer from radiation to ions due to the ultraviolet line absorption; and the coronal model of Thomas (1973), and Hearn (1975), where the wind is sustained by gas pressure in a hot corona around the star. As both models do not completely account for the observations, several complementary modifications have been suggested. The nowaday situation is reviewed by Cassinelli and Lamers (1978), and Conti (1978).
Of-WN evolution: spectral types and effective temperatures
Authors: Leep E. Myckky
Published: July 2016

Because of the growing evidence (Conti 1976, Snow and Morton 1976, Chiosi et al. 1978, de Loore etal. 1977) that some Of stars are evolving into WN stars, we reexamine the classification of WN stars. There are four schemes for classifying WN stars, those of the IAU (1938), Hiltner and Schild (1966), Smith (1968), and Walborn (1974). All of these schemes involve estimating by eye the ratio of the nitrogen line strengths. Walborn's scheme is the most useful because he avoids problems that may arise from the use of helium lines. In other respects Walborn's scheme gives WN classifications similar to those found by Smith.
Conservative and non-conservative evolutionary computations in connection with Wolf-Rayet binaries.
Authors: Vanbeveren D. , De Grève J.P. , de Loore C. , van Dessel E.L.
Published: July 2016

We consider the evolution of massive close binaries. The reader is referred to the first contribution by the same authors during this conference for the general ideas. The present contribution deals with the implications for the Wolf-Rayet phase, i.e. that part of the evolution where the primary is liable to show W-R characteristics (as usual the primary is defined as the originally more massive component). We refer to the evolution after the exchange of mass between the components, or even during the exchange phase (see section 3).
An out-of-plane CO survey of the first galactic quadrant
Authors: Cohen R. S. , Tomasevich G. R. , Thaddeus P.
Published: July 2016

We are undertaking at Columbia University an out-of-plane survey of 2.6 mm CO emission from the first quadrant of the galactic disk with a 1.2 meter telescope. With the 8′ beamwidth of this instrument at 2.6 mm (about that of the largest existing steerable instruments at 21 cm) it is possible to completely map the first quadrant in only a few hundred days of observation.
Optical HII regions
Authors: Georgelin Y. M. , Georgelin Y. P. , Sivan J.-P.
Published: July 2016

The ionized hydrogen regions seen on monochromatic Hα photographs of nearby spiral galaxies (e.g. Fig. 1) can be divided into four classes (Monnet, 1971): (1) bright, condensed, classical HII regions; (2) diffuse emission in the arms surrounding and connecting the classical regions (emission measure (EM) ∼ 150 cm−6 pc, for a gas electron temperature of 6000 K); (3) much fainter, diffuse emission extending over the entire disk (EM ∼ 50 cm−6 pc) in most Sc and Sd galaxies; (4) diffuse emission in the nuclear region.
Galactic dust and extinction
Authors: Lyngå Gösta
Published: July 2016

The ratio R between visual extinction and colour excess, is slightly larger than 3 and does not vary much throughout our part of the Galaxy. The distribution of dust in the galactic plane shows, on the large scale, a gradient with higher colour excesses towards 1=50° than towards 1=230°. On the smaller scale, much of the dust responsible for extinction is situated in clouds which tend to group together. The correlation between positions of interstellar dust clouds and positions of spiral tracers seems rather poor in our Galaxy. However, concentrated dark clouds as well as extended regions of dust show an inclined distribution similar to the Gould belt of bright stars.
A mechanism for the origin and development of spiral arms in a galaxy
Authors: Pişmiş Paris
Published: July 2016

It is generally believed that the constituents of a galaxy like ours are formed from an isolated gaseous assembly at successive stages, starting from a spheroidal sybsystem down to the flattest subsystem.
The galactic density wave, molecular clouds and star formation
Authors: Bash Frank N.
Published: July 2016

A model has been devised for the orbits of molecular clouds in the Galaxy. The molecular clouds are assumed to be launched from the two-armed spiral-shock wave, to orbit in the Galaxy like ballistic particles with gravitational perturbations due to the density-wave spiral-potential and each cloud is assumed to produce an identical cluster of stars. A comparison of the model with observations suggests that each cloud radiates detectable 12C160 (J = 1 → 0) spectral line radiation from birth to an age of 30 million years and that stars are seen in the cloud 15 million years after its birth. The model has been tested by comparing its predicted velocity-longitude diagram for CO against the observed one for the Galaxy and by comparing the model's predicted surface brightness in the UBV photo metric bands against observed surface photometry for Sb and Sc galaxies.
Gaseous response to bar-like distortions
Authors: Roberts William W.
Published: July 2016

In this review the large-scale dynamics of the gas in a model disk galaxy which has an oval, bar-like distortion (or bar structure) in the inner parts is reviewed from the standpoint of recent gas dynamical studies, both steady state and time evolutionary.
The four-armed response near the Lindblad resonances in galaxies
Authors: Contopoulos G.
Published: July 2016

We show that there is an important four-armed term in the response of a flat galaxy to an imposed two-armed spiral field near the Inner and Outer Lindblad Resonances.
The galactic circular velocity near the sun
Authors: Einasto J. , Haud U. , Jôeveer M.
Published: July 2016

The conventional value of the galactic circular velocity near the Sun is Vo = 250 km s−1 (Schmidt 1965). Recently both lower (Mathewson) et al., 1974; Einasto et al., 1976) and higher (Lynden-Bell and Lin, 1977) values have been suggested. The following summarizes our dynamical determinations of Vo. Altogether six independent methods have been used.
Statistical modeling of CO emission in the galaxy
Authors: Gordon M. A. , Burton W. B.
Published: July 2016

We summarize here some of the distribution properties of CO clouds in our galaxy as determined by observation and by computer simulations of these observations. The simulations adequately account for the number of clouds, their spatial separation, and their relative velocities with respect to one another. The principal shortcoming of the axisymmetric simulations is their failure to describe adequately the clustering of clouds seen in the velocity-longitude domain.
Implications for star formation in spiral galaxies from observations of nearby molecular cloud complexes
Authors: Elmegreen Bruce G.
Published: July 2016

I want to make three points about star formation in spiral galaxies that follow from consideration of the internal structure of giant molecular cloud complexes (GMCC). The first point comes from pressure considerations. The total pressure inside the star-forming core of a GMCC may be written 106k)v/3kms−1)4(17pc/D)2 for virial theorem line width v and cloud diameter D; the pressure from a spiral density wave shock (SDWS) is 105 k(ns/1cm−3)(vs/20kms−1)2 and the thermal pressure in the cloud is 104 k(n/103cm−3) (T/10K) for Boltzmann constant k. These three pressures differ by factors of 10. An SDWS has too low a pressure to affect a cloud core; the only way an SDWS could influence a GMCC is if it interacted with the low thermal pressure in the cloud, i.e., the SDWS could propagate into a cloud along the direction of a magnetic field which may be the source of large scale pressure in a transverse dimension. The second point is that the density and mass of a GMCC are so large that the cloud will enter an SDWS like a cannon ball and will not be readily deflected. GMCC in other galaxies would then look like spurs on the spiral pattern and not like dust lanes. The alternative to these two points is that an as yet undiscovered (or uncommon) population of low density (100cm−3) clouds exists involving GMCC-type masses, or that smaller clouds coalesce at the SDWS. This implies that the star-forming clouds studied by molecular observers would be post-SDWS and post-gravitational collapse objects. Finally, the maximum age of a GMCC in the solar neighborhood is probably less than 50 million years. Its destruction is a result of pressure forces from the stars which it creates. Destruction in this sense does not necessarily imply that the molecules are converted into atoms – only that the cloud is pushed around. In the solar neighborhood, some clouds may, in fact, turn into 21-cm features; e.g., an HI half shell with a radius of 100 pc and a visual extinction through the shell of 0.2 mag. contains 3×105 M⊙, the mass of a GMCC. However, in the 5-kpc ring of the Galaxy, there is too much H2 relative to HI to allow any cycling between H2 and HI that is in phase with an SDWS unless the cloud remains molecular for 80% of the cycle. More likely, the cloud will be “destroyed” before that time. The implication is that cloud destruction at 5 kpc must produce molecular shells in addition to some atomic shells. This could be observed.
On the mass density distribution of the inner galaxy
Authors: Maihara T.
Published: July 2016

Based on current 2.4-micron observations of the Galaxy (see Okuda et al. in this Symposium), we have proposed a specific model for the bulge component. This model is a concentric spheroid with an axial ratio of ∼0.5; ρ(a)∞(a2+ac2)−1exp(-(a/ao)2), where ao = 2.5 kpc and ac = 0.14 kpc respectively. A constant mass-to-luminosity ratio M/Lv≃7.6 is assumed, which yields the relevant rotational velocity in the inner region (Figure 1); the absolute velocity is normalized to 250 km s−1. This value of M/Lv is likely to meet with giant-rich synthetic models for the nuclear bulge of M31.
Dynamical interpretations of the galactic center region
Authors: Sanders Robert H.
Published: July 2016

I will define the central region of the Galaxy as being the inner four kiloparsecs. The distinguishing characteristics of this region are:

1)

The dominance of a central spheroidal component in the mass distribution – a bulge.

2)

An apparent deficiency of gas, at least between radii of 500 pc and 4000 pc.

3)

High non-circular gas velocities. Now let us consider these characteristics in some detail.