bluuebunny/crossref_metadata_2025 huggingface dataset:
Spectral Classification in the Small Magellanic Cloud
Authors: Dubois P. , Jaschek M. , Jaschek C.
Published: July 2016

This paper presents results obtained in classifying 26 supergiants of the Small Magellanic Cloud. The main results are:

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The hydrogen lines are not as sharp as expected for such luminous stars.

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Generally, for the A-type stars, the calcium K-line is too strong compared to the other metallic lines.

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There are differences in the behaviour of the different metals.

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Often, the stars present variations in their spectra.

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50% of the stars brighter than mv = 11.3 have an enhancement of the H8 Balmer line, which is one of the characteristics of a shell star.

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The comparison with the Radcliffe classification and Dachs classification is, except in very few cases, in good agreement.
Remarks on Some Aspects of Spectral Classification
Authors: Morgan W. W.
Published: July 2016

The present state of MK spectral classification is described briefly.
A Catalogue of [Fe/H] Determinations
Authors: Morel M. , Bentolila C. , Cayrel G. , Hauck B.
Published: July 2016

A catalogue resulting from the compilation of published values of iron/hydrogen abundances is given for 515 stars.
Conference Summary: Molecules in astrophysics
Authors: Herbst Eric
Published: July 2016

A summary of the conference is presented along with some outstanding problems and challenges for future work.
Ices in star forming regions
Authors: Tielens A.G.G.M. , Whittet D.C.B.
Published: July 2016

IR spectra of sources associated with molecular cloud material show a variety of absorption features attributed to simple molecules, such as H2O, CO, CH3OH, CO2, CH4, and OCS in icy grain mantles. These identifications are reviewed. These molecules are formed through accretion and reaction of gas phase species on grain surfaces. The high abundance of CH3OH and CO2point towards the importance of hydrogenation and oxidation reactions in this process. Observations also show that thermal outgassing is of great importance for the composition of interstellar ice mantles. Both these processes are discussed in some detail.
Observations of “Hot Cores”
Authors: Ohishi Masatoshi
Published: July 2016

Recent observational results toward the “Hot Core” sources (Orion KL, SgrB2, G34.3+0.15, W51, and so on) are summarized. Several saturated organic molecules are commonly observed among these sources, and these results favor formations on the grain mantles followed by evaporation. Some results of surveys in “hot core molecules” are presented. Such molecules may be used as diagnostics to establish the presence of “hot core” regions.
Models of hot molecular cores
Authors: Millar T.J.
Published: July 2016

We review the properties of hot molecular cores with specific reference to chemical modelling. While most theoretical modelling has been generic, we discuss models for two specific sources, G34.3+0.15 and W3 (H2O). We show that the hot core gas in both these regions has an age of 5 103 — 104 yrs and that the abundances of many molecules are consistent with formation in the gas-phase following evaporation of simple molecular ices from the grains. We end with a discussion of current problems and future directions.
Non thermal sputtering of grains and production of SiO in interstellar shocks
Authors: Pineau Des Forêts Guillaume , Flower David
Published: July 2016

We present recent results for the yields of Si and O, produced in the sputtering of SiO2 by ions of different masses, and show the importance of sputtering by heavy particles at low streaming velocities. These data are incorporated in a C-shock model to study the erosion of interstellar grains and the release of silicon through non-thermal sputtering within the shock. Once in the gas phase, the atomic silicon reacts with O2 and is rapidly transformed into SiO. The column densities of SiO thus calculated are compared with the observations of molecular outflows with a satisfactory agreement. In the postshock gas, SiO disappears from the gas phase through the reaction SiO(OH,H)SiO2 and SiO2 remains, unseen, in the cold dense gas. This could explain the extremely low upper limits of SiO deduced from observations of dark clouds.
Photon dominated regions: Observations of [C I] and CO
Authors: Keene Jocelyn , Lis D. C. , Phillips T. G. , Schilke P.
Published: July 2016

Since the construction of the first specialized submillimeter telescopes nearly a decade ago, there has been extensive mapping of astronomical sources in the previously difficult to observe ground-state fine-structure transition of [C I] at 492 GHz. We discuss recent CSO observations of [C I] and 13CO (2 → 1) lines toward bright photon-dominated regions (PDRs). These observations have revealed an interesting effect. In many sources and over a broad range of column densities, the observed intensity of the [C I] line is proportional to that of the 13CO (2 → 1) line with exceptions mainly in dense, active star-forming regions, where C I appears to be under-abundant relative to 13CO. In this paper we quantitatively display this effect.
Modeling of interstellar surface processes
Authors: Buch V. , Devlin J. P.
Published: July 2016

Computational modeling is discussed of some interstellar surface processes. The surface of interstellar grains is envisaged as covered by at least several layers of weakly bonded molecular material. Simulated amorphous ice particles were used to model interaction of such surfaces with gas, including sticking of H and D atoms, and adsorption of H2. A possibility of microporosity of interstellar ice mantles is discussed.
New dust features in oxygen-rich envelopes
Authors: Waters L.B.F.M.
Published: July 2016

We report on the discovery of new solid state emission features in the ISO-SWS spectra of evolved oxygen-rich stars. These features appear in cool dust shells and are probably due to crystalline forms of silicates, and crystalline water ice.
Cool star models
Authors: J⊘srgensen Uffe Gråre
Published: July 2016

It is the intention with the present review to summarize the role of molecules in cool stars. Which molecules do we find there, which are the most important ones, what do we know about them, what more would we like to know? – and what are the current main problems and progresses we meet when including molecules in models of cool stars ?
Appendix 2: Molecular data bases
Authors: Van Dishoeck E.F.
Published: July 2016

Astrochemistry makes enormous demands on laboratory and theoretical chemistry to obtain line frequencies, molecular parameters and rate coefficients for chemical reactions under interstellar conditions. The astrophysical needs for such large data bases continue to increase. For example, spectral line surveys at submillimeter wavelengths routinely contain thousands of rotational lines, whereas high resolution infrared and optical data require large amounts of information on vibrational and electronic transitions. The astrophysical modeling, both of interstellar clouds and of the envelopes and photospheres of stars, has improved to the stage that highly accurate molecular data are essential.
Flares of Red Dwarf Stars and Solar Activity
Authors: Gershberg R. E.
Published: July 2016

The UV Cet-type star flares and the chromospheric flares of the Sun have many important common features. Both types of events are very transient; they occupy only small parts of the stellar surfaces; in both cases the optical as well as the radio emissions of the flares have strong similarities in temporal and spectral characteristics. Evaluations of electron temperatures, electron densities and the general character of mass motions within radiating gas in the stellar flares also display similarities to solar flares. The solar and stellar atmospheres where the flares develop have many important common characteristics too: the existence of hot chromospheres and coronas above much colder photospheres, the absence of noticeable dust envelopes, the photospheres patched with dark short-lived spots, and some periodicity in spot appearance over several years. The facts permit one to identify the processes which take place during separate solar and stellar flares and which are responsible for the solar and stellar activities in total. From this point of view some general problems of physics and evolution of red-dwarf flare stars are discussed.
T Tauri and FU Orionis Stars
Authors: Gahm G. F.
Published: July 2016

A great deal of information on the continuous radiation of T Tau- and similar type stars has been acquired. The cause of the ultraviolet and infrared excess emission is discussed. The possibility that the blue continuum may arise from numerous line emissions is considered. Various possibilities for the cause of the light variations are described, as well as the nature of the emission lines. The special features of the FU Ori stars are mentioned.
Spectroscopic and Photometric Observations of VX Cas
Authors: Zajtseva G. V. , Kolotilov E. A.
Published: July 2016

The light variation in V, B — V, U — B is shown and the change in the Hα, Hβ emission-line profiles is described.
Physical Interpretation of Light Curves of R Coronae Borealis-Type Stars
Authors: Krełowski Jacek
Published: July 2016

The paper contains preliminary results of theoretical investigations of the light curves of RCB variables. A circumstellar dust envelope is assumed to be the source of the great visual opacity as well as the infrared and violet excesses. The processes of grain formation and the interaction with the radiation field are discussed briefly. The results of a laboratory experiment concerning the problem of the violet continuum are also described.
Observations of R CrB and XX Cam
Authors: Totochava A. G.
Published: July 2016

The observations of R CrB and XX Cam obtained in 1971–1973 are described. Semiregular light variations with an amplitude of and a period of about 30 to 40 days were found during maximum brightness. In addition, fluctuations up to for about 2 h were observed.
Stars of δ Scuti-Type in Stellar Clusters
Authors: Breger Michel
Published: July 2016

The frontier of our knowledge of δ Scuti variables is reviewed with emphasis on the following topics: (1) pulsation in specific clusters; (2) rotation and pulsation in different clusters; (3) metallicism and pulsation; and (4) periods and pulsation modes of δ Scuti stars.
U Geminorum-Type Stars
Authors: Gorbatsky V. G.
Published: July 2016

The light variations, properties of U Gem binary systems, outbursts of U Gem systems, and evolution and related problems are discussed.

Recent high-speed photometry of Z Cha is mentioned in an addendum.
Spectroscopic Observations of Z Andromedae and CI Cygni from 1968 to 1973
Authors: Mammano A. , Rosino L. , Yildizdogdu S.
Published: July 2016

A description is given of the spectral changes observed in the symbiotic stars Z And and CI Cyg during the nova-like outbursts of 1968 and 1971–73. The observed features can be interpreted by assuming that transient shells are formed around the hot component of a binary system, imbedded in a small nebula.
The Crab Pulsar as a Component of a Binary System
Authors: Tsygan A. I.
Published: July 2016

This note discusses the properties of the Crab pulsar assuming that it is moving in the gravitational field of the second component.
Red Variables of the Halo and the Globular Clusters
Authors: Evans T. Lloyd
Published: July 2016

The present state of knowledge of the red variables in the halo and globular clusters is summarized. Techniques for their discovery are described. The correlations between their properties and those of the globular clusters to which they belong are discussed. The evolutionary state of the variables is considered and stars are assigned tentatively to the first or second ascent of the giant branch or to the excursions from the asymptotic giant branch resulting from instabilities in the He-burning shell.

The assumption that a recognizable type of variable represents a unique type of star leads to the conclusions that the bulk of the stars in the central bulge of the Galaxy are more metal-rich than 47 Tuc and that the Large Magellanic Cloud contains an old, moderately metal-deficient population similar to that represented by clusters such as 47 Tuc in the Galaxy while the Small Magellanic Cloud does not.
Energy Distributions of Be Stars: (Review Paper)
Authors: Schild R. E.
Published: July 2016

Energy distributions from 0.32 to 1.06 μ for field Be stars having p designations in their spectral types show that stars with Balmer discontinuities in emission do exist. Furthermore, the filling in of the Balmer continuum near the discontinuity is usually observed. The continuum emission showing a peak near 1 μ is a common feature in the energy distributions presented here.

Energy distributions for a number of bright field Be stars are also presented and discussed.
Ultraviolet Observations of Be Stars: (Review Paper)
Authors: Heap Sara R.
Published: July 2016

The history of ultraviolet studies of Be stars is barely ten years old. However, in the last decade, twelve major space experiments have observed Be stars in the ultraviolet region of the spectrum, and ultraviolet data for over 30 Be stars are now available in the literature. Table I shows some of the characteristics of the experiments. They include two rockets, five astronomical satellites, three manned satellites, and one planetary probe. Except for the rocket experiments, they are primarily survey instruments, which have provided ultraviolet data on early-type stars in general, and these data have proved to be extremely useful as standards of comparison for Be stars. Of the twelve spacecraft, two are presently operating: Copernicus and ANS. The two experiments complement one another very nicely in that the ANS experiment can obtain absolute continuous flux distributions, while the Princeton experiment can obtain high-resolution line spectra for the brighter Be stars.
Polarization Measurements Across the Balmer Lines of Be and Shell Stars
Authors: McLean I. S. , Clarke D.
Published: July 2016

We have made linear polarization measurements of several Be and shell stars across the Hα and Hβ lines, all of the stars exhibiting polarization in the continuum, the emphasis here being on measurements made of ζ Tau, 48 Per, φ Per, and γ Cas. Three types of results ensue: some stars show no significant change of polarization across the Balmer features (e.g., 48 Per, X Per); some stars show a reduced polarization across the features (e.g., γ Cas, ζ Tau) indicating the presence of intrinsic polarization; some stars show a change in the degree of polarization but with a marked rotation of the direction of vibration (e.g., φ Per, 48 Lib) which can be attributed to a combination of non-aligned intrinsic (circumstellar) and interstellar polarizations. Interpretations of these results are discussed, and we demonstrate the potential power of line profile polarimetry/photometry as an important new method for separating intrinsic and interstellar polarization effects, thus enabling polarization observations to be used as a constraint on models of Be stars.
Radiative Transfer in Dynamic Stellar Atmospheres
Authors: Klein Richard I.
Published: July 2016

In order to understand the Be star phenomenon, and move in directions away from ad hoc models, detailed calculations have been made that treat nonlinear hydrodynamics self-consistently with non-L.T.E. radiative transfer.
Two Types of Evolution of Massive Close Binary Systems
Authors: De Loore C. , De Greve J. P.
Published: July 2016

It is well known that the outcome of case B evolution of the primaries of massive close binary systems (M1 ≥ 9 M⊙) depends on the initial primary mass. The most massive primaries finally ignite carbon, form iron cores and presumably end in a supernova explosion, whereas the lighter ones presumably end as white dwarfs, without carbon ignition. This paper derives an estimate of the mass boundary separating these two kinds of evolution.

As an example of the first case, the evolution of a 20 M⊙ + 14 M⊙ system was computed; after the mass exchange, the primary star (with M = 5.43 M⊙) evolves through the helium-burning (Wolf-Rayet) stage towards a supernova explosion; finally the system evolves into an X-ray binary (BWRX-evolution).

As a representative for the second case the evolution of a 10 M⊙ + 8 M⊙ system was examined. After the first stage of mass exchange, the primary (with a mass of 1.66 M⊙) approaches the helium main sequence; during later phases of helium burning the radius increases again, and a second stage of mass transfer starts; after this the star (with a mass of 1.14 M⊙) again evolves towards the left in the Hertzsprung-Russell diagram and ends as a white dwarf (BSWD-evolution). A system of 15 M⊙ + 8 M⊙ is found to evolve very similar to the 20 M⊙ + 14 M⊙ system. The mass Mu, separating the two types of evolution, must therefore be situated between 10 and 15 solar masses. An initial chemical composition X = 0.70, Z = 0.03 was used for all systems.
Effect of Instantaneous Mass Ejection on Orbital Elements of Circular Binaries
Authors: Mitalas R.
Published: July 2016

All attempts to fit the binary pulsar PSR 1913 + 16 into an evolutionary scenario consider the effect of an instantaneous mass ejection on the orbital elements of a circular binary.
Spectroscoscopic Observations of Southern Dwarf Novae
Authors: Vogt N.
Published: July 2016

The first image-tube spectra of five dwarf novae and one old nova are described and compared with the colours of these stars.
Spectroscopic Observations of U Gem
Authors: Smak J. I.
Published: July 2016

Radial velocities of U Gem have been measured from individual components of the emission lines of the Balmer series, Ca II K, and He 14471, originating in the gaseous disk and in the hot spot of this binary system. These new data give K1 ≅ 143 km s−1 and Vdisk sin i ≅ 530 km s−1. The resulting mass of the primary component is m1 = 1.1 ± 0.4 m⊙ and the mass-ratio m2/m1 = 0.6 ± 0.2. Radial velocities and intensities of the emission components originating in the hot spot are also discussed.
Theory of Dwarf Novae
Authors: Bath G. T.
Published: July 2016

Recent work on the physical processes resulting from mass transfer between the red and blue components of dwarf nova binaries is reviewed. The optical behaviour of the blue component's accretion disc suggests that it may be the infall, accretion energy which is being liberated during outbursts. Theoretical results which suggest that the red component may suffer quasi-periodic mass transfer instabilities are discussed. The resulting accretion disc properties are considered and compared with the observed optical outburst behaviour for the simplest steady state disc models. The complexity of the interaction between the two stellar components in these systems is emphasized.
Mass Transfer Rates in Algol Binaries Deduced from Their Period Changes
Authors: Hall D. S. , Neff S. G.
Published: July 2016

Average mass transfer rates in 23 Algol binaries are derived by analyzing their observed period changes within the framework of the Biermann-Hall period change model. These are compared with thermal mass loss rates computed from the dimensions which the cooler (mass-losing) component had at the onset of mass outflow. The agreement is quite good and confirms a claim made earlier that the subgiant components in Algol binaries are losing mass at a rapid (thermal) rate, not at a slow (nuclear) rate.
Unsteady Mass Loss in Close Binaries
Authors: Webbink R. F.
Published: July 2016

The evolution of a system of 1.50M⊙ and 0.50M⊙ components with initial separation 3.00R⊙ is presented. The primary reaches its Roche lobe after 6.108 × 108 yr, and the mass loss rate grows quickly to ~ 1.1 × 10−7M⊙ yr−1. The deep convective envelope of the secondary contracts in response to accretion, however, and the system avoids contact, even though the main sequence mass-radius relationship crosses the Roche relationship at 0.758M⊙.

The growth of the convective envelope of the primary with mass loss prevents thermaltimescale mass transfer from reaching any stable value. The mass loss rate continues to increase as a result of the tendency of the growing convective envelope to expand with mass loss. A Bath-type pulsational instability in the mass transfer rate is manifested as a longer-period thermal instability in the hydrostatic treatment. Eventually mass loss proceeds on a dynamical timescale, reaching 1.5 × 10−4M⊙yr−1. This is followed by a detached phase with the mass ratio not yet reversed, and a second dynamical episode leaving a 0.6666M⊙ + 1.3334M⊙ binary still in a semi-detached state. The original secondary, now more massive, has a surface luminosity of 0.0538L⊙ but a nuclear luminosity of 1540L⊙, and a convective core of 1.076M⊙ separated by a radiative zone of only 0.028M⊙ from its convective envelope.

An attempt is made to follow the evolution of the secondary in the case where the stream energy, much greater than the intrinsic luminosity of the secondary, is dissipated spherically symmetrically at its surface. The outer envelope departs radically from the previous case, an optically deep radiative surface layer forming, and the convection zone splitting into two, the lower one remaining very massive. Because the mass transfer timescale is short compared with the thermal timescale of the secondary, however, it is concluded that the stream luminosity cannot significantly alter the evolution of the secondary.
Four-Colour Survey of W-UMa-Type Systems
Authors: Rucinski S. M.
Published: July 2016

Four-colour photometry of 24 W UMa-type systems is presented.
Numerical Studies on the Stability of the Solar System
Authors: Nacozy Paul
Published: July 2016

In this paper, recent numerical and analytical results of the author and others, concerning the stability of the solar system are presented. The results indicate that the actual planetary system could possibly have stable and bounded motion.
The Satellite Case of the Three-Body Problem
Authors: Hori Gen'ichiro
Published: July 2016

In the lunar or satellite theory, the disturbing function is developed in the form in which each term consists of two factors. The first factor depends on the position of the sun, and the second one that of the satellite.
Present Status of the Astronomical Ephemeris
Authors: Aoki Sh. , Sinzi A. M.
Published: July 2016

The IAU (1976) System of Astronomical Constants and a new set of fundamental theories will expectedly be introduced into the international and national ephemerides for the volumes of 1984 onwards. In order to avoid any confusion in the future, it is necessary to manifest the character of the data published in the current volumes of the Astronomical Ephemeris = American Ephemeris, both abbreviated as A.E. With this end in view, computer programs for the calculations of the ephemerides of the Sun and inner planets based on the Newcomb's (1895, 1898) Tables have been prepared at Tokyo Astronomical Observatory (TAO) and Hydrographic Department of Japan (JHD) independently of each other using different computers and hence different types of FORTRAN. JHD has further prepared the programs for the Moon's ephemerides based on the Brown-Eckert theory and has reproduced the Eckert, Brouwer and Clemence's numerical integrations of the outer planets. Fundamental ephemerides thus calculated are compared with those data tabulated in the A.E. for the year of 1975, as an example, in the present paper.
Solar System Occultation Predictions Using Automated Microdensitometry Techniques
Authors: Shelus P. J. , Benedict G. F.
Published: July 2016

The development of automatic, computer-controlled, electronic equipment, under the direction of an intelligent user, has significantly affected the output of scientific knowledge from astronomical research. This increased output is as much a result of the easing and/or elimination of heretofore tedious tasks as it is a result of vast increases in data acquisition rates via observing systems which make more efficient use of in-coming electromagnetic radiation. One such automated system (Shelus et al, 1977) has been implemented by the present authors to predict occultations of stars by Solar System objects. In the past these predictions have been a time consuming task which was made even more onerous since only a very few observable phenomena were found. Perhaps of even more importance is that, since candidate objects to be occulted typically were obtained from star catalogs, such a search was incomplete. Note that phenomena involving stars fainter than normal catalog limits are certainly relevant in the cases of Uranus, Neptune, Pluto, minor planets and the natural satellites of the major planets.
Review of the Theories of Motion of the Natural Satellites
Authors: Message P. J.
Published: July 2016

Most of the natural satellites of the planets of the solar system may be put into one of three main groups, according as to which of three main influences dominate the perturbation of their motion from Keplerian motion about the primary planet. The first of these is the attraction of the Sun, which governs the perturbations of the Moon's motion about the Earth, and those of the outer satellites of Jupiter (satellites VI to XIII), and Saturn's satellite Phoebe. The second is the departure of the gravitational field of the planet from that of a spherically symmetric body (the “figure terms”), and this governs the perturbations of the two satellites of Mars, Jupiter's satellite Amalthea (V), Neptune's satellite Triton, is probably the most important influence on Uranus' satellites, and is important, though not dominant, for the inner satellites of Saturn. The third influence is the mutual attraction of the satellites themselves. An order of magnitude argument suggests that periodic perturbations from this cause could scarcely be expected to be measureable from Earth, were it not that the frequent appearance of small-integer near-commensurabilities of pairs of orbital periods, and the consequent argumentation of the associated perturbations by a variety of types of resonance effects, in the systems of Jupiter and Saturn, causes mutual perturbations to dominate the orbital theories of three of the four great satellites of Jupiter, and six of the nine satellites of Saturn, and enables the masses of most of the satellites involved to be determined with otherwise unexpected relative precision (in some favourable cases, of the order of one per-cent) from Earth based data. Let us now consider the satellite systems of each of the outer planets in a little more detail.
The Rings of Saturn and Uranus
Authors: Goldreich Peter
Published: July 2016

Nature has presented us with two systems of planetary rings. They are not at all similar. Saturn has bright, broad rings separated by narrow gaps. The rings of Uranus are dark, narrow and widely spaced. Presumably both sets of rings lie inside the Roche limit and this is why the ring material has not condensed into satellites.
Hyperperiods, Orbital Stability, and Solution of the Problem of Kirkwood Gaps
Authors: Kiang T.
Published: July 2016

I believe I have solved, at least in principle, the long-standing problem of the Kirkwood gaps, and have incidentally initiated a new approach to questions of orbital stability. I shall begin with the concept I call hyperperiod. A given periodic dynamical system S with period P may or may not have a latent long period - the hyperperiod P∗. If P∗ exists, then any small displacement or variation, actual or virtual, once-for-all or recurrent, will induce a displacement y which will be periodic with period P∗ and will be of bounded amplitudes. We can then say that S is stable. If P∗ dose not exist, then y will eventually become indefinitely large - and we say that S is unstable.
Physical and Dynamical Evolution of Long-Period Comets
Authors: Weissman Paul R.
Published: July 2016

Oort (1950) first suggested that the source of the long-period comets is a large spherical cloud of comets surrounding the solar system and extending roughly halfway to the nearest stars. The observational evidence for this is the distribution of original inverse semi-major axes of the long-period comets which shows a large spike of comets at very small positive values of 1/ao, less than 10−4 AU−1. Attempts to model the evolution of these comets by Oort in his original paper, by Kendall (1961), Shteins (1961), and Whipple (1962) were successful in recreating the general shape of the 1/ao distribution. However in each case the authors were unable to match the observed ratio of new comets from the Oort cloud versus older comets evolving under the influence of planetary perturbations.
Some Statistics on Long-Period Comets
Authors: Hasegawa I. , Shimizu T.
Published: July 2016

Distributions of the original reciprocal semimajor axes l/a and the perihelion distances q of eighty “new” comets (Marsden et al, 1978) are discussed from the view point of a hypothesis of the interstellar origin (Hasegawa, 1976).
The O stars: optical review
Authors: Hutchings J. B.
Published: July 2016

I would like to start with a quick overview of the O stars - their significance and role in the galaxy and in astrophysics - just to remind ourselves of why we are here and what we hope to talk about. In Table 1 I show a rough outline of the contribution of O stars to what happens in the galaxy as a whole. Because of their extreme luminosity, they contribute a large fraction of the radiation of the galaxy, while forming a very tiny group of objects and mass. Because of their short lifetime they are a population that has gone through 104 generations in the life of the galaxy. Their high mass loss rates may account for a large fraction of the new matter injected into the interstellar medium, and they probably power some significant fraction of the hard X-ray sources in the galaxy, by virtue of the fact that a companion can become a neutron star a) without disrupting the binary and b) while the companion is still a mass losing O star.
Mass loss of B1Ia-O supergiants and evolutionary consequences
Authors: Wolf B. , Sterken C.
Published: July 2016

The superluminous B supergiants are loosing mass and their progenitors are supposed to be O stars between 03 and 06 and hence it is justified to talk about B1Ia-O supergiants in this Symposium. Extensive high dispersion spectroscopic observations of four luminous B1 supergiants of the southern hemisphere have been carried out during 1972 and 1975 at ESO, La Silla. Some characteristic data of the program stars are summarized in Table 1.
Radio emission from flows
Authors: Schwartz P. R.
Published: July 2016

Many emission line stars are radio sources including early type stars such as ζ Pup and P Cyg, peculiar objects such as MWC 349 (a possible proto-planetary system) and V1016 Cyg, nebular variables such as T Tau, and at least one late M giant. These “radio stars” are characterized by (1) a rising spectrum with spectral index α = 0.6 to 1.1, (2) positional coincidence between star and radio source, and (3) no rapid (less than 107 sec) time variability. These characteristics are in contrast with the non-thermal spectrum and rapid variability of Algol type “radio stars” and the radio emission associated with x-ray sources. The radio component of the spectrum of emission line stars originates in the substantial mass loss flows which are a feature of their outer atmospheres and which, when ionized by stellar radiation, radiate by free-free electron thermal bremsstrahlung. These circumstellar H II regions are, in general, detectable with present radiotelescopes if the characteristic size of the optically thick region of the flow is greater than about 10−7 of the distance to the star.
Observations of velocity fields in WN and Of stars
Authors: Niemelä Virpi S.
Published: July 2016

Systematic wavelength shifts of series of spectral line centers observed in many early type stars, generally interpreted as due to large scale motions, can give us information about the velocity gradients in stellar atmospheres. However, it should be borne in mind that the velocity gradients inferred from the observed displacements of spectral lines may not correspond to a unique alternative (e.g. see Karp 1978). Also, and especially when we are dealing with stars which have emission lines in their spectra, the structure of the velocity field depends on the assumed temperature structure of the atmosphere, i.e. in which atmospheric region do the lines originate.
The distribution of formaldehyde in the galaxy
Authors: Davies R. D. , Few R. W.
Published: July 2016

A deep survey of formaldehyde absorption along the galactic plane has been made using the MkII telescope (beamwidth 9 arcmin). Observations were made with 1° spacing between ℓ = 14° and 36° and 2° spacing elsewhere in the longitude range 8 to 60. Integration times were typically 7 hr; the rms noise was 4 mK.
Spectral-line sky surveys from the NASA-JPL SETI project
Authors: Knapp G. R. , Kuiper T.B.H.
Published: July 2016

The Jet Propulsion Laboratory (California Institute of Technology) has recently begun preparations for a modest SETI (Search for Extra-Terrestrial Intelligence) project at radio wavelengths. The proposed project is two-fold: (1) to search the entire sky visible from Goldstone, California (site of one of the NASA Deep Space Network Stations), i.e. that north of δ ∼ −30°, at all frequencies between 1 and 24 GHz using a horn receiver and (2) to carry out a more sensitive sky search at a few selected frequency bands, using dedicated 26 and 10m antennas. The search will be for signals of the type unlikely to be produced by natural causes, e.g. narrow spikes in frequency space. The basic rationale behind this search is discussed by Murray, Gulkis and Edelson (1978).
The galactic distribution of 60 young open clusters
Authors: Fenkart Rolf P.
Published: July 2016

The photometric distances of 60 young galactic clusters (with sp < b3), all observed in UBV or RGU, have been calculated or recalulated according to “method A” (Becker, 1963). The galactic distribution of these clusters, shown in Figure 1, confirms their role of being good spiral tracers.
Galactic nonthermal radiation. Distribution of SNRs and pulsars
Authors: Wielebinski R.
Published: July 2016

All sky surveys of the radio continuum emission give us the basic information on the distribution of the nonthermal emission in the Galaxy. At metre wavelengths, where nonthermal emission is dominant, good angular resolution is difficult to attain. For many years the best surveys near 2 m wavelength gave us a picture of the galaxy with ∼ 2° resolution. At centimetre wavelengths, where arc min resolution is available, the intense HII regions dominate the radio sky. Supernova remnants have a distribution somewhat similar to that of the discrete HII regions and must be delineated by various methods in high resolution galactic plane surveys in the decimetre wavelength range.
An ejection theory of spiral structure
Authors: Schmidt-Kaler Th.
Published: July 2016

A number of questions was posed at this Symposium: why is the density of molecules highest near R = 5 kpc? Why is star formation most active near 5 kpc? The life-time of the molecular clouds near 5 kpc is about 2·108 years - where does the gas come from? Why is almost no gas observed between R = 1 and 3 kpc?
Rotation curves of high-luminosity spiral galaxies and the rotation curve of our galaxy
Authors: Rubin Vera C.
Published: July 2016

Rotation curves of high luminosity spiral galaxies are flat, to distances as great as r=49 kpc. This implies a significant mass at large r. Rotational velocities increase about 20 km/s across a spiral arm, as predicted by the density wave theory. By analogy, it is suggested that our Galaxy has a flat rotation curve out to r∼60 kpc, with V ∼ constant at near the solar rotational velocity, and m ∼7×1011 m⊙. Values of A and B imply that the sun is not located in a spiral arm.
Recent evidence on the rotation curve of our galaxy for R > RO
Authors: Jackson P. D. , FitzGerald M. P. , Moffat A. F. J.
Published: July 2016

Studies of the rotation curve of our Galaxy at galactocentric radii, R, greater than the solar distance, Ro, from the center require the use of conventional optical techniques since the distances to as well as the radial velocities of Population I objects are needed.
Age variations of the mean angular momentum
Authors: Grosb⊘l P. J.
Published: July 2016

The mean angular momentum of stars in the solar vicinity with respect to the galactic center shows a significant change as a function of age. In figure la the variation is given for B stars using the Strömgren index [u-b] as abscissa since it depends nearly linear on the logarithm of the age (i.e. the interval corresponds approximately to 7.7 < log(age) < 8.2). This can be explained by a change in the birthrate as a function of place, velocity and time and/or an azimuthal variation in the galactic potential. To investigate if the presence of a density wave potential could cause the observed distribution a number of models were made. In these models stars were formed close to the spiral arms according to the density wave theory and traced back to the present epoch. The mean angular momentum of stars being within 300 pc from the sun is shown in figure lb where the amplitude of the wave was 5 percent, the inclination angle and one arm coincided with the Sagittarius arm. For a pattern speed Ωp= 13.5 km/s/kpc the observed values could be reproduced quite well which indicats the existence of a density wave in our Galaxy.
Stability of an interstellar medium with curved magnetic field lines
Authors: Cesarsky Catherine J.
Published: July 2016

Parker (1966) has considered a simple equilibrium state of the interstellar gas and fields system, such that the magnetic field lines are parallel to the galactic plane; he has shown that this state is subject to the Rayleigh-Taylor instability. The gravitational pull of the stars on the gas and the buoyancy of the magnetic field tend to bend the field lines, allowing the gas to slide down towards the plane. The stability of equilibria with curved magnetic field lines remained to be considered.
Observations of the near infrared survace brightness distribution of the galaxy
Authors: Okuda H. , Maihara T. , Oda N. , Sugiyama T.
Published: July 2016

Studies of the stellar distribution in the inner region of our Galaxy have been seriously hampered at optical wavelengths by strong interstellar extinction. The extinction decreases considerably at infrared wavelengths, allowing us to look deep into the Galaxy. Motivated by this, we have tried to observe the near infrared brightness distribution of the central region of the Galaxy (Okuda et al., 1977, Maihara et al., 1978, Oda et al., 1978). Similar observations have been carried out by Hayakawa et al., (1976), Ito et al., (1977), and Hofmann et al., (1977). These observations have provided valuable information on the distributions of stars and dust in the inner Galaxy (Hayakawa et al., 1977, Maihara et al., 1978, Oda et al., 1978).
Galactic mass modeling
Authors: Einasto J.
Published: July 2016

Galactic mass modeling has a long history. The first mass models were designed to represent the galactic attraction force in the radial direction. Considerable progress in galactic mass modeling was made during the fifties when Kuzmin (1952) introduced nonhomogeneous ellipsoids and Schmidt (1956) used a number of ellipsoids to represent various galactic populations. Further progress in galactic mass modeling has followed with the improvement of the system of the galactic constants and with the improvement of our knowledge of the structure of the galactic populations, in particular with the discovery of a massive corona around the Galaxy. In this report we present a new mass model of the Galaxy. It has been constructed using the most recent data available. A preliminary version of this model has been discussed earlier by Einasto, Jôeveer and Kaasik (1976).
A sensitive high-velocity HI survey
Authors: Giovanelli Riccardo
Published: July 2016

The observational studies of the neutral hydrogen high velocity clouds (HVC's) in the last decade have for the most part concentrated on the detailed study of the prominent complexes discovered by the surveys of the late 1960's. More recently, several HVC's were discovered, often by accident, with very high velocities, which are typically outside of the velocity range and below the sensitivity limit of the old surveys. The tendency to associate these clouds with the closest galaxy at hand became a rather common practice. The idea that the Local Group, or the Local Supercluster, is populated with such “intergalactic clouds” was fed by these discoveries, and generalized to the whole field of the HVC's. I have repeatedly argued against the latter generalization (Giovanelli 1977, 1978). In this paper I shall report on the progress of a new survey that intends to constitute a test of the intergalactic approach itself.
A non-establishment view of the Symposium
Authors: Sinha R. P.
Published: July 2016

Many interesting new results from studies of external galaxies as well as of the Milky Way Galaxy have been presented at this meeting. I shall confine my remarks to but a few observations which appear to be crucial in deriving an acceptable picture of the large scale structure in the Galaxy.
Dynamical Theory of Spherical Stellar Systems with Large N
Authors: Spitzer L.
Published: July 2016

The dynamical evolution of a spherical star system is attractive to the theorist for two reasons. In the first place the physical problem, with some idealization, appears to have an appealing, if somewhat deceptive, simplicity; a large number of point masses, attracting each other with inverse-square gravitational forces, are assumed to move in a quasi-steady system with spherical symmetry. In the second place, the observed globular clusters appear to conform rather closely to this ideal of a spherical star system; to analyze the changes of these clusters with time, resulting from the dynamical interaction of stars with each other, is surely an important aspect of the theory of galactic evolution.
Homology in the Evolution of Cluster Cores
Authors: Lynden-Bell D.
Published: July 2016

It is pointed out that in advanced phases of evolution the cores of clusters ought to evolve homologously and reasons are sought as to why this evolution should be at constant core energy. It is pointed out that continued evolution after infinite core densities have been achieved is an important area for future research.
N-Body Simulations
Authors: Aarseth S. J.
Published: July 2016

Numerical results on escape and binary evolution in N-body systems are summarized and some results of a new calculation with initial binaries are described.
The Simulation of Non-Isolated Expanding Gravitational Systems
Authors: Janin G. , Haggerty M. J.
Published: July 2016

Numerical experiments on the gravitational N-body problem are reviewed for the case of non-isolated systems. The effect of an external field on expanding cubical systems is discussed.
The Structure of Round Stellar Systems: Observation and Theory
Authors: King Ivan R.
Published: July 2016

In addition to its traditional roles of checking theories and applying them, observation also plays an important role in guiding theory and indicating the form that it should take. This paper reviews types of observation, types of stellar system (omitting the highly flattened ones), and the relations between them. Observational limitations are indicated, as well as places where observations of particular sorts are needed, either for guidance of theories or for their application.
The 6C Survey
Authors: Baldwin J. E.
Published: July 2016

A new survey of radio sources at 151 MHz, which has not been described previously, is in progress at Cambridge. There are several of us working on it including Warner, Kenderdine, Waggett, Masson and Mayer. The results of the first observations are at present in a preliminary state but we hope that in time they will form the first part of the 6C survey. The purpose of the survey is not to reach the faintest sources detected so far in aperture synthesis observations but to study moderately faint sources at a low observing frequency and to cover a large part of the northern sky rapidly. The deepest survey made so far at a low frequency is that of Ryle and Neville (1962) at 178 MHz over a region of 50 square degrees near the north celestial pole. The faintest sources detected had flux densities of 0.25 Jy, corresponding to a source density of 104 sr−1. It is already 15 years since that survey, which was the first trial of aperture synthesis using the earth's rotation, and much more is now technically possible. One of the most interesting features of a low frequency survey is its ability to detect preferentially sources with steep radio spectra and to be sensitive to sources of very low surface brightness. We know that in many cases these two properties go together and are associated with old radio sources, or at least with those parts of sources which are old. Many of the weak radio galaxies in nearby clusters are obvious examples of this type of source while the final, and so far unidentified, stages of the development of the most powerful double sources may be exciting candidates for discovery.
Westerbork Surveys of Radio Sources at 610 and 1415 MHz
Authors: Willis A. G. , Oosterbaan C. E. , Le Poole R. S. , de Ruiter H. R. , Strom R. G. , Valentijn E. A. , Leiden Sterrewacht , Katgert P. , Katgert-Merkelijn J. K.
Published: July 2016

The Westerbork Synthesis Radio Telescope (WSRT) has now been used to make source surveys at frequencies of 610 and 1415 MHz. This paper summarizes the results concerning source counts and anisotropies in the distribution of sources from those surveys not concerned with clusters of galaxies.
The Flux Density-Angular Size Distribution for Extragalactic Radio Sources
Authors: Swarup G. , Subrahmanya C. R.
Published: July 2016

The median values of angular sizes of weak extragalactic radio sources, the flux densities of which lie in the range of about 0. 3 to 5 Jy at 327 MHz, have been determined for a new sample of 119 sources observed during 1973-74, and agree well with the value of about 10 arc sec determined earlier by Swarup (1975). For 8 different flux density ranges, the angular size distribution for the All-sky, 3CR and Ooty radio sources have been compared with theoretical predictions based on the evolutionary model by Kapahi (1975) and show a remarkable agreement with his model except that the best fit is found for a linear size evolution proportional to (l+z)−1.
Interpretation of Cosmological Information on Radio Sources
Authors: Burbidge G.
Published: July 2016

The topic that I have to introduce today is concerned with the question as to whether or not we can obtain any cosmological information from radio astronomy. Alternatively, we may ask “Where does radio astronomy have an impact on cosmology?” There are several areas that must be discussed. They are:

1)

The discovery and interpretation of the microwave background radiation.

2)

The identification of powerful radio sources and the discovery that many of them have large redshifts. If we can prove that the large redshifts mean that the objects are at great distances, then we can use these radio sources as follows:

(a)

We can attempt to obtain a Hubble relation for the optical objects which are identified with radio galaxies;

(b)

We can look for a relation between the angular diameters of the radio sources and the redshifts of the optically identified objects and we can also look at relations between the angular diameter and the radio flux;

(c)

We can construct log N - log S curves and we can carry out luminosity volume tests.