bluuebunny/crossref_metadata_2025 huggingface dataset:
How High a Density is for Photoionization in AGN?
Authors: Zheng Wei
Published: June 2019

At a density of 1011cm−3 or higher, the column emissivity of many lines, such as hydrogen Balmer lines, may not continue to increase with density because the strong radiative transfer results in a “skin effect” near the illuminated front. The Lyα to Balmer line ratio is larger than at lower density.
Infrared [FeII] and H2 Line Emission in Active Galactic Nuclei
Authors: Moorwood A.F.M. , Oliva E.
Published: June 2019

Infrared spectra around [FeII](1.644μm), H2 (v = 1-0 S(1) at 2.121μm) and Brγ (H 7-4 at 2.167μm) have been obtained of 35 emission line nuclei whose optical spectra range from pure HII regionlike to Seyfert 1. All three emission lines have been detected in a large fraction of those nuclei exhibiting starburst activity but not in “pure” Seyferts. The highest detection frequency, however, was found for composite nuclei showing evidence for both starburst and Seyfert activity. Several arguments suggest that both the [FeII] and H2 are shock excited and could be largely attributed to supernova remnants. The fact that the [FeII]/Brγ and H2/Brγ ratios tend to be somewhat larger in composite than in pure starburst nuclei, however, plus significant spatial displacements between the [FeII] and H2 emitting regions found recently during follow-up observations of selected galaxies suggest that large scale phenomena, e.g. SN winds or mass outflows from AGN, may also be important.
Optical and Far-Infrared Properties of UM Survey Emission-Line Galaxies
Authors: MacAlpine Gordon M. , Salzer John J.
Published: June 2019

For the University of Michigan (UM) survey, the Curtis Schmidt telescope at CTIO is used with Kodak IIIa-J plates and the 1.°8 objective prism to detect emission-line galaxies (ELGs) and quasars. Line emission is the primary selection criterion. The quasar sample has been investigated by Lewis, MacAlpine, and Weedman (1979) and by MacAlpine and Feldman (1982) while a study of the ELGs was begun by Lewis (1983). Here, we report on a more extensive analysis of the 172 ELG candidates in the UM Lists IV (MacAlpine and Lewis 1978) and V (MacAlpine and Williams 1981) areas.
Infrared Emission from Radio Galaxies
Authors: Impey C. D. , Wynn-Williams C. G. , Becklin E. E.
Published: June 2019

Observations with the IRTF and IRAS indicate that there are at least two different mechanisms for the generation of infrared emission from radio galaxies.
The Origin of the 25 μm Emission in Seyfert 2 Galaxies
Authors: Dultzin-Hacyan D. , Moles M. , Masegosa J.
Published: June 2019

We have made a statistical study of the optical and far-IR properties of all the Seyfert 2 galaxies in the catalog by Véron-Cetty and Véron (1987; hereafter VCV). Nuclear spectroscopic data were compiled from the literature and IR fluxes from the Catalogued Galaxies and Quasars Observed in the IRAS Survey (1985); we used only those IR fluxes not flagged as limits or uncertain values. We have used for comparison four more lists of objects with IRAS fluxes: one of Seyfert 1 galaxies given by Rodríguez Espinosa, Rudy and Jones (1987), a list of LINERs compiled from the literature, a sample of “normal” spirals (those labeled H in Keel, 1983), and finally the galaxies catalogued as Starburst nuclei galaxies in VCV.
The Twin-Nucleus Merging Galaxy MKN 266
Authors: Hutchings J.B. , Neff S.G. , van Gorkom J.H.
Published: June 2019

We present results of observations of the double-nucleus galaxy Markarian 266 (NGC 5256) from 3 principal sources. These are

1:

CCD imaging with the Canada-France-Hawaii telescope in broad and narrow bands. These indicate that the galaxy has extended, complex, faint outer plumes which indicate that a recent merger has occurred. The narrow-band images reveal remarkable knotty structure of the [O III] emitting gas, extending over the whole central part of the galaxy. This is not seen in Hα (see figure 1).

2:

21cm imaging with the VLA, covering velocity space near that of the optical nuclei. The continuum image reveals resolved triple structure, with the two outer peaks coincident with the optical nuclei. The 21cm velocity profiles indicate the presence of considerable H I absorption near the optical emission line velocities.

3:

Spatially resolved optical spectroscopy with the DAO 1.8m telescope. These data reveal the details of the [O III] velocity field and some of the physical parameters of the gas. The complexity and extended nature of the gas explains some conflicting redshift measurements in the literature. Together with the imaging data, we derive estimates of nuclear reddening and luminosity.
Color Maps of A 1795 and A 2597 - Cooling Flow Cluster Central Galaxies with Active Nuclei
Authors: Romanishin W.
Published: June 2019

The subject of cooling flows in clusters of galaxies remains a controversial one, primarily because many clusters which have large x-ray derived mass inflow rates do not show any optical manifestation of the inflow or of the final fate of the gas. However, a handful of cooling flow clusters do show extended blue continuum regions indicative of current star formation which may be caused by the cooling flows (Romanishin 1987, Romanishin and Hintzen 1988), while another group show spectral evidence of star formation (O'Connell and McNamara 1988). Most of the cluster galaxies which show evidence of star formation also show nuclear activity, in the form of radio emission.
Gas Disks in Radio Galaxies
Authors: Simkin S. M. , Sadler Elaine M.
Published: June 2019

Spectroscopic observations have shown that strong radio galaxies contain extra–nuclear gas which is rapidly rotating (Simkin 1979, Heckman et al. 1985). In addition, weak spiral-like structure has been observed in the inner regions of several strong radio galaxies classified as DE or E (Simkin and Michel 1986, Beichman et al. 1985, Hansen et al. 1987, Baum et al. 1988).
Morphology and Luminosity Distribution of Seyfert Galaxies
Authors: Pastoriza M. G. , Mediavilla E. , Battaner E.
Published: June 2019

V and I CCD images for 13 Seyfert galaxies have been obtained at the Cassegrain focus of the JKT at the Roque de los Muchachos Observatory, Canary Islands. Integrated V and I magnitudes were obtained sampling the intensity of each galaxy in a circular area, up to a radial distance R at which the V surface brightness is 24 mag/sq arcsec. Mean luminosities MV = −21.89 and MI = −22.92 have been calculated adopting the galaxian radial velocities given by Adams (1977) and Ho = 55 kms−1 Mpc−1. By using elliptically averaged V and I luminosity profiles and the most outstanding morphological features from isophote maps we can distinguish two groups: 1) Galaxies with prominent bulge (Mk 50, Mk 124, Mk 348 and 3C227) where almost the entire profile is fitted by an r−1/4 law and no evidence for an exponential disk is found; some have a very diffuse external structure, like Mk 50 and Mk 348; and 2) Spiral galaxies (Mk 9, Mk 10, Mk 79, Mk 110, Mk 352, Mk 358 and Mk 618) showing spiral arms and exponential disks; most of them have also a prominent bar. Mk 42, whose luminosity profiles are strongly disturbed by a bright external ring, and NGC 985 a galaxy with a single arm, were both included in this group.
Optical Spectra of Low Flux Radio Sources
Authors: Koo D. C. , Kron R. G. , Windhorst R. A.
Published: June 2019

Low flux radio sources are important for a variety of reasons. In principle, a 1 mJy survey that is over 1000 times fainter than the 3CR allows us to reach objects 20 times more distant, almost literally to the edge of the universe, or to detect much less luminous sources at the same distances. We can hope to detect primeval galaxies, to check the idea that objects with redshifts z greater than 3 or 4 are optically hidden by dust, to detect new populations of radio objects, to possess pointers to distant clusters and galaxies, as well as to understand better the AGN phenomenon.
VLA Observations of an Optically Deep Sample of Molonglo Quasars: Aspect Dependence of the Optical Continuum
Authors: Kapahi V.K. , Subrahmanya C.R. , D'Silva S.
Published: June 2019

Quasars found in low frequency radio surveys are often assumed to have their jet axes randomly oriented in the sky because relativistically beamed radio cores rarely contribute significantly to the total flux density at metrewaves. But an orientation bias can still arise from the optical magnitude limit of the sample (Kapahi & Shastri 1987) if radio beaming is accompanied by an enhancement of the optical continuum as well (due to beaming or other effects). Such a bias can explain the finding (de Ruiter et al. 1986) that the typical value of R (ratio of core to extended flux density at 5 GHz) for the magnitude limited Bologna sample is about 5 times larger than for 3CR quasars, eventhough both samples are from low frequency surveys. It is thus consistent with the unified scheme for quasars (Orr & Browne 1982; Kapahi & Saikia 1982), which in fact requires an aspect dependence of the optical continuum (eg. Browne & Wright 1985; Browne & Murphy 1987).
Planetary Nebulae in the Magellanic Clouds
Authors: Webster B. Louise
Published: June 2019

Selection effects in the search for planetary nebulae in the Magellanic Clouds have not seriously distorted the observed space distribution, but have affected the apparent excitation classes. A difference between the properties of the SMC and LMC planetaries remains. A group of high-excitation nebulae with strong lines of He and N has been isolated. If these are excluded, the helium abundance appears to be normal in each Cloud. The oxygen abundance in LMC planetaries is about half the Orion value and may be even lower in the SMC objects. The significance of the abundances, excitation classes and space distribution is briefly discussed.
Emissivities of Fe III and Fe VI and Iron Abundances in Planetary Nebulae
Authors: Garstang R.H. , Robb W. Derek
Published: June 2019

We have calculated electron impact excitation cross sections between most of the low metastable levels of the 3d6 configuration in Fe III and of the 3d3 configuration in Fe VI have also been computed. The statistical equilibrium equations have been solved for a range of electron temperatures and electron densities, and the resulting level populations used to calculate emissivities for the forbidden lines of Fe III and Fe VI. Comparisons with observed line intensities and abundance determinations in planetary nebulae are in progress. (Paper submitted to The Astrophysical Journal.)
Optical Histories of Some Possible Embryonic Planetary Nebulae
Authors: Feldman P.A. , Purton C.R.
Published: June 2019

From the list of stellar emission-line objects which exhibit radio spectra characteristic of uniform radial mass outflow, we have selected those objects which might be considered possible embryonic planetary nebulae. Our criterion was to choose those mass outflow objects with exciting stars of the types'characteristic of central stars of non-stellar (i.e., normal) planetary nebulae. These objects are Hb 12, Hen 1044, HD 167362, and possible M2-9, Vy 2-2, and Hl-23.
The "Butterfly" Nebula M2-9: Its Possible Relation to B[e] Stars and Proto-Planetaries
Authors: Andrillat Y. , Swings J.P.
Published: June 2019

M2-9 is not a bona fide planetary, nor simply a star: it most probably is a planetary nebula in the formative stages. High densities, the presence of [01], Fell and [Fell] emission lines, and prominent infrared continua are characteristic of such objects. There is a striking progression of their spectra from B[e] stars such as HD45677 to M2-9 itself; Merrill's class of objects intermediate between Be stars and planetary nebulae is represented e.g. by MWC 645, HD 51585, V 1016 Cygni, HM Sagittae, and MIVC 349. Remarkable similarities exist between the spectra of the latter objects and that of M2-9, especially in the recently covered region between 8000 and 11000 Å which is rich in emission lines of the Paschen series, of Hel, 01, [SIII], Fell and [Fell] (Andrillat and Swings, 1977, in preparation).
Origin of protogalactic eddies
Authors: Chernin A. D.
Published: June 2019

A highly excited state of the cosmic medium might develop in the isotropic Big Bang starting with weak irrotational perturbations that were likely to be of entropy type. Supersonic matter currents are an indispensable feature of this state. Initial irrotational gas motions become vortical when they become supersonic. One can expect that this may provide a clue in galactic cosmogony (1970, Nature, 226, 440).
Personal View - the Large Scale Structure of the Universe
Authors: Longair M. S.
Published: June 2019

I should explain at once that I very much regret that it is the Chairman of the Scientific Organising Committee who has been press-ganged by his Committee into giving the concluding remarks at this symposium. I obviously cannot take an unbiassed view of the proceedings. I have therefore refrained from calling this a “survey” or “concluding remarks” - it is a personal view of those aspects of this symposium which have struck me as particularly interesting - I will make no attempt to provide a complete survey of the last five days.
Recent Observations of Organic Molecules in Nearby Cold, Dark Interstellar Clouds
Authors: Suzuki H. , Ohishi M. , Morimoto M. , Kaifu N. , Friberg P. , Irvine W. M. , Matthews H. E. , Saito S.
Published: June 2019

We report recent investigations of the organic chemistry of relatively nearby cold, dark interstellar clouds. Specifically, we confirm the presence of interstellar tricarbon monoxide (C3O) in Taurus Molecular Cloud1 (TMC-1); report the first detection in such regions of acetaldehyde (CH3CHO), the most complex oxygen-containing organic molecule yet found in dark clouds; report the first astronomical detection of several molecular rotational transitions, including the J=18−17 and 14−13 transitions of cyanodiacetylene (HC5N), the 101−000 transition of acetaldehyde, and the J=5−4 transition of C3O; and set a significant upper limit on the abundance of cyanocarbene (HCCN) as a result of the first reported interstellar search for this molecule.
Panspermia - A Modern Astrophysical and Biological Approach
Authors: Greenberg J. Mayo , Weber Peter
Published: June 2019

For the first time a laboratory simulation of the effect of the interstellar environment has been used to provide quantitative estimates of bacterial spore survival in the space between the stars. In the diffuse regions between clouds ten percent survival is limited to at most hundreds of years although one in ten thousand may survive for several thousand years. Within common dense clouds the ten percent life expectancy is extended to tens of millions of years because of the severely reduced ultraviolet within these clouds as well as because of the accretion of ultraviolet absorbing mantles on the spores. The random motion of molecular clouds is shown to provide a possible vehicle for transport of spores from one solar system to another. The most hazardous times in such a journey are at the start and finish and, although the requirements for survival during these periods are quantified here, the possibility or probability of their being satisfied remains pure conjecture.
No Valid Evidence Exists for Interstellar Proteins, Bacteria, etc.
Authors: Davies R. E. , Delluva A. M. , Koch R. H.
Published: June 2019

The claims for large biological molecules and for prokaryotic and eukaryotic organisms in the interstellar medium are summarized. These claims are compared with new UV laboratory spectra of numerous specimens. The results are incompatible with these claims.
Astronomical Sources of Circularly Polarized Light and Their Role in Determining Molecular Chirality on Earth
Authors: Wolstencroft Ramon D.
Published: June 2019

The major source of circularly polarized flux potentially capable of inducing asymmetric photolysis of a racemic mixture of chiral molecules on the primitive Earth is the daytime sky. The degree of circular polarization (q) depends on the slope and orientation of the local terrain which obscures part of the sky. After allowance for dilution by direct sunlight values of |q| range between about 10−4 and 10−5. The rates of (1) asymmetric photolysis, (2) chiral selection by the electro-weak process and (3) racemization are not yet well enough known for the relative importance of these processes to be definitely established.
Universal Aspects of Biological Evolution
Authors: Ball John A.
Published: June 2019

Which biological laws, if any, might be universal?
Search for Strongly Polarized Radio Emission from E.T.I., and an Optimist Approach to the Great Silence (Fermi's Paradox)
Authors: Vallée J.P.
Published: June 2019

A summary is made of a program to scan slowly a band of sky in search of strongly linearly polarized radio signals from E.T.I. communication relays. Despite this and numerous other observational searches, no signals have been found. An optimist approach to this great silence (Fermi's Paradox) is developed.
On the Inevitability and the Possible Structures of Supercivilizations
Authors: Kardashev Nikolai S.
Published: June 2019

Since civilizations face always problems that require continuously greater activity, it is likely that supercivilizations will undertake activities and construct structures of a very large scale. Properties and means of detections of such superstructures and activities are discussed. We also examine six possible scenarios on the evolution of civilizations.
An Infrared Search in our Solar System as Part of a More Flexible Search Strategy
Authors: Papagiannis Michael D.
Published: June 2019

One of several explanations for the Fermi Paradox is that the whole Galaxy, including our Solar System, has already been colonized, but that for a variety of reasons the extraterrestrials have chosen not to reveal their presence. In a universal search for extraterrestrial intelligence, it seems prudent to check-out also our own backyard. IRAS has obtained a large volume of infrared data at 12, 25, 60 and 100 microns from which a special working group at JPL, of which the author is a member, is trying to establish a special catalogue of Solar System objects, the vast majority of which are asteroids. A careful search through this data bank for objects with peculiar infrared spectra would be the first step in the search for major artificial objects, such as space stations or materials processing plants, in our Solar System. The asteroid belt is an ideal source of raw materials for space colonies, which could have easily escaped detection lost among the many thousands of natural asteroids. Checking them out for excesses in the infrared is an ideal screening test for artificial objects in our Solar System.
Dynamical Evolution of Multi-Component Clusters
Authors: Inagaki Shogo
Published: June 2019

Presence of stars with disparate masses causes great differences in the dynamical evolution of star clusters from the evolution of single component clusters. One remarkable effect is acceleration of the evolution. Another effect is destabilization or stabilization. In two-component clusters equipartition at the cluster centre is nearly achieved if Spitzer's (1969) condition is satisfied. In multi-component clusters equipartition at the cluster centre is achieved if either the range of stellar mass is very narrow or the mass spectrum is very steep. Global equipartition is never achieved. Post-collapse evolution of multi-component clusters is discussed briefly and some remained problems are presented.
Gravothermal Oscillations
Authors: Bettwieser Erich
Published: June 2019

Stellardynamical systems are modelled by gaseous spheres. The properties of an isothermal equilibrium configuration with a central singularity are discussed in the context of post-collapse evolution. For the numerical calculations heating effects are taken into account. Evolution towards the equilibrium configuration is monotonically only if much energy is delivered from hardening processes of binary stars. Since the equilibrium configuration is gravo-thermally unstable a minute emission of energy is sufficient to turn gravothermal contraction into gravothermal expansion. In such case equilibrium is approached by oscillations of the core.
Binary Formation and Interactions with Field Stars
Authors: Hut Piet
Published: June 2019

Binaries provide an energy source in dense stellar systems. Exothermic gravitational interactions in star clusters can play a role similar to that of nuclear reactions in single stars. These gravitational interactions can be modeled in a laboratory setting, in the form of numerical binary-single star and binary-binary scattering experiments. Gravitational cross sections obtained this way can be applied to model star cluster evolution, just as nuclear cross sections are used as input data in stellar evolution calculations. References are given to detailed descriptions of gravitational cross sections, and a useful new example of an application is given: the rate at which hard binaries form in a homogeneous stellar background, as the solution of an integral equation describing the combined effects of creation, destruction, hardening and softening of binaries.
Why are Stellar Systems Anisotropic?
Authors: Bettwieser E. , Fricke K. J. , Spurzem R.
Published: June 2019

Spherical stellar systems show during their secular evolution the development of velocity anisotropy in their halo (cf. e.g. Hénon, 1971). The present study examines the general reasons for generation of anisotropy in stellar systems by means of a gaseous star cluster model including anisotropy. Moment equations of the Boltzmann equation are considered for spherical symmetry in coordinate space but not in velocity space closed in third order by a heat flux equation. The coefficient of heat conductivity is tailored to describe the flux of energy due to the cumulative effect of distant gravitative encounters and generalized to include effects of anisotropy and external gravitation by a massive central object (Bettwieser et al., 1984).
Post-Newtonian treatise on the rotational motion of a finite body
Authors: Fukushima T.
Published: June 2019

The definition of the angular momentum of a finite body is given in the post-Newtonian framework. The non-rotating and the rigidly rotating proper reference frame(PRF)s attached to the body are introduced as the basic coordinate systems. The rigid body in the post-Newtonian framework is defined as the body resting in a rigidly rotating PRF of the body. The feasibility of this rigidity is assured by assuming suitable functional forms of the density and the stress tensor of the body. The evaluation of the time variation of the angular momentum in the above two coordinate systems leads to the post-Newtonian Euler's equation of motion of a rigid body. The distinctive feature of this equation is that both the moment of inertia and the torque are functions of the angular velocity and the angular acceleration. The obtained equation is solved for a homogeneous spheroid suffering no torque. The post-Newtonian correction to the Newtonian free precession is a linear combination of the second, fourth and sixth harmonics of the precessional frequency. The relative magnitude of the correction is so small as of order of 10−23 in the case of the Earth.
Algebraic manipulations on computers for lunar and planetary theories
Authors: Henrard Jacques
Published: June 2019

A new software to handle the large expressions involved in high accuracy analytical theories has been developped by H. Claes, M. Moons, J.M. Zune and J. Henrard. The main ideas on which this software is based are described here.
Numerical planetary and lunar ephemerides: present status, precision and accuracies
Authors: Standish E. Myles
Published: June 2019

The Ephemeris Development Program has been in existence for nearly 20 years at JPL, providing high precision present-day knowledge of the positions of the moon and major planets. The resultant ephemerides are used extensively in the navigation of spacecraft and in the reduction of astrometric observations. They also provide a key element in the testing of various theories of gravitation and a means for the determination of various relevant astronomical constants. The ephemerides and the process of creating them are both shown to be viable tools for the measurement of various gravitational effects which govern the motions of the objects in the solar system.

This paper gives an outline of the least-squares adjustment of the ephemerides to the observations, the present physical (dynamical) model, the present observations to which the ephemerides are fit, the expected accuracies of various ephemeris elements, recent and future observations and features of the solar system which are poorly determined (and thereby place limits upon the accuracies). Recent comparisons with similar work at the Center for Astrophysics (formerly at MIT) are serving as valuable independent checks on formulations and procedures used at each institution; they also lend insight toward what are the realistic accuracies being attained. The export procedure, by which an outside user may obtain and use the JPL ephemerides, is described.
The theory of the motion of Halley Comet
Authors: Akim E.L. , Koljuka Ju.F. , Savtchenko V.V. , Stepanianz V.A. , Ivanov N.M. , Tikhonov V.F.
Published: June 2019

The theory of the motion of Halley comet has been built using ground optical positional observations of 1682, 1759, 1835, 1910 and 1982–84. The orbital elements of the comet and two coefficients characterizing non-gravitational perturbations were determined precisely as a result of the statistical treatment of the observations. The estimations of the accuracy of the theory and the data describing its agreement with the observations are presented. The theory has been applied to ballistic-navigational calculations for the Soviet Vega project.
Systematic differences between planetary observations and ephemerides
Authors: Seidelmann P. K. , Santoro E. J. , Pulkkinen K. F.
Published: June 2019

This paper is a summary of the referenced complete paper which includes figures and references.
Predictions of occultations by minor planets as a test of accuracy
Authors: Kristensen Leif Kahl
Published: June 2019

Predictions of tracks of occultations of stars by minor planets give a strong test of the accuracy of observations, star places, and dynamical theories. A critical discussion of the 1983 September 11 occultation of 14 Piscium by (51) Nemausa shows that the systematic regional errors of fundamental stars introduce errors in the long-term predictions of occultations that are larger than relativistic effects.
Relativistic effects included in the apparent positions of fundamental stars (APFS)
Authors: Lederle T. , Schwan H.
Published: June 2019

The relativistic effects included in the APFS from 1984 onwards are described. They are discussed in comparison with the accuracy available with modern techniques of observation.
The motion of a geosynchronous satellite
Authors: Bhatnagar K. B.
Published: June 2019

The motion of a geosynchronous satellite has been studied under the combined gravitational effects of the oblate Earth (including its equatorial ellipticity), the Sun, the Moon and the solar-radiation pressure. It is observed that the orbital plane rotates with an angular velocity the maximum value of which is 0.058°/yr. and regresses with a period which increases both as the orbital inclination and the altitude increase. The effect of earth's equatorial ellipticity on the regression period is oscillatory whereas that of Solar-radiation pressure is to decrease it.

The synchronism is achieved when the angular velocity of the satellite is equal to the difference between the spin-rate of the Earth and the regression rate of the orbital plane. With this angular velocity of the satellite, the ground trace is in the shape of figure eight, though its size and position relative to the Earth change as the time elapses. The major effect of earth's equatorial ellipticity is to produce a change in the relative angular position of the satellite as seen from the Earth. If the satellite is allowed to execute large angle oscillations the mid-point of oscillation would be at the position of the minor axis of the earth's equatorial section. The oscillatory period T has been determined in terms of the amplitude Γ and the tesseral harmonic J2(2). From this result we can determine the value of J2(2) as T and Γ can be observed accurately.
Does the energy density of the vacuum influence planetary motions?
Authors: Shubert R.
Published: June 2019

New cosmological and quantum mechanical evidence for the existence of an ether has made it appropriate to investigate again the effect of such a medium upon the motions of planets and satellites within the solar system. The properties of a medium of this kind are as yet unknown except that it may be the ultimate origin of inertia and therefore that it may have a fundamental link to the gravitational force.
Luminous Blue Stars: Distribution and Numbers
Authors: Garmany Catharine D.
Published: June 2019

Because the term “luminous blue stars” is relative, let me begin by delineating what region of the H-R diagram I am considering. For the purpose of this talk, I will discuss primarily 0-type stars, with Teff > 30,000 K and Mbol > − 7, but I will also mention their evolved descendants the B supergiants with 30,000 K > Teff > 10,000 K and Mbol > −8, and their even later evolutionary form, the Wolf-Rayet (W-R) stars with Teff > 30,000 K and uncertain Mbol. Although these stars are not among the visually brightest stars, they are the bolo-metrically most luminous as well as the hottest stars. They are also the most massive. They are an important channel in the metal enrichment in a galaxy through the action of mass loss via stellar winds and their ultimate disruption as supernovae (Maeder 1981). They also contribute in a major way to the energy balance of the interstellar medium (Abbott 1982).
The Light Variations of the Red Supergiant Mu Cephei
Authors: Mantegazza Luciano
Published: June 2019

The causes of light variations in red supergiants are still discussed. In particular it is not clear if these variations result from deterministic or narrow-band stochastic (pseudo-periodic) processes or from a mixture of both types.
Simulations of the Brightest Stars in Galaxies as Distance Indicators
Authors: Greggio Laura
Published: June 2019

The brightest stars in galaxies have been often considered useful as distance indicators. However, one may expect that the absolute magnitude of the brightest stars in galaxies should depend on the IMF and on the present SFR, and that statistical effects may be important, although different in different photometric bands, due to the different numbers of objects effectively sampled.
The dependence of the stellar rate of mass loss on effective temperature and velocity
Authors: de Jager C. , Nieuwenhuijzen H. , van der Hucht K.A.
Published: June 2019

From the existing literature data have been collected on the stellar rate of mass loss for 189 stars with known or derived values of the effective temperature Teff and luminosity L. It appears that Ṁ depends only on Teff and L for the O- through M-type stars brighter that about 3 × 103 L⊙. This is shown in Figure 1, where we have plotted for each star the value of - log(-Ṁ) with Ṁ expressed in solar masses per year. An interpolation formula has been derived for the Ṁ(Teff, L) dependence. If we define X = log Teff-4, and Y = log(L/L⊙-5, then
The Mass Loss Rate of SK 80 (07Iaf) in the Small Magellanic Cloud
Authors: Willis A J , Howarth I D , Nandy K , Morgan D H
Published: June 2019

The star SK 80 in the SMC is classified as 07Iaf by Walborn (1976) who notes that it is the only confirmed Of star in that Galaxy known to date. A knowledge of the mass loss properties of OB stars in the Magellanic Clouds is of interest because of the recent evidence that such stars show reduced mass loss properties than their galactic counterparts (Hutchings 1980) and for Of stars because of the possible link between such stars and Pop I transition WNL stars (Conti 1976).

We have secured HIRES IUE and optical spectra of SK 80 and have attempted to derive the mass loss rate from these data.
Physical Processes in Massive Star Formation
Authors: Silk Joseph
Published: June 2019

The gravitational fragmentation theory of star formation is reviewed. Theoretical arguments are presented which suggest that the lower stellar mass cut-off to the IMF in giant HII regions may be as high as 10 M⊙. Mechanisms for bimodal star formation are described in the context of a coagulation model for formation of the giant molecular clouds, and application is made to starbursting galaxies.
Systems of Stellar Associations in Galaxies
Authors: Hodge Paul
Published: June 2019

This paper begins with an attempt to examine the problem of identifying stellar associations in galaxies in a consistent way, so that meaningful physical comparisons can be made for the population of stellar associations of different galaxies. A compilation of the existing data on associations in other galaxies is given and their properties compared. Questions relating to star formation in stellar associations are discussed, and then the issue of the initial mass function of core clusters, especially those located in giant HII regions, is briefly examined.
The Distribution of Bright Stars in the SMC Clusters
Authors: Kontizas E. , Theodosiou E. , Kontizas M.
Published: June 2019

Star counts can be used to investigate radial distribution of stars of different mass. Relaxation through stellar encounters is a mechanism that does make a distrinction between stellar masses, so systems that have undergone such relaxation should show differences in distribution between stars of high and low mass. That does not happen for systems that have undergone an initial violent relaxation since this type of relaxation treats all masses equally.
Kinematics of the Galactic Inner Spheroid
Authors: Gilmore G. , Wyse R.
Published: June 2019

Analysis of the detailed photometric, kinematic and chemical properties of stellar populations constrains the formation history of the Galaxy. We have completed a photometric survey and initiated a spectroscopic survey, obtaining radial velocities and abundances for volume complete samples of spheroid dwarfs in situ, to distances of a few kpc. Three fields under study are those for which Chiu (Ap. J. Suppl. 1980) obtained proper motions - SA 57 (NGP), SA51 (anticenter field) and SA68. Two of these fields are on the sun - Galactic center meridional plane (SA57 and SA51) so that (U,V) and (V,W) components of space motion respectively may be derived on the basis of the proper motions alone, once distances have been obtained. Our initial distance estimates are from Chiu's photometry and population classes, which are based on the position of the star on the reduced proper motion diagram.
A Search for Gravitational Lensing
Authors: Hewitt J. N. , Langston G. I. , Mahoney J. H. , Burke B. F. , Turner E. L. , Lawrence C. R. , Bennett C. L.
Published: June 2019

Gravitational interactions allow one to investigate the nature of matter in the universe independent of the properties that make it luminous. Much as studies of the dynamics of galaxies and clusters of galaxies have indicated the presence of dark matter, gravitational lensing provides an independent probe of the large scale distribution of dark matter in the universe.
An Upper Limit on the Masses of Galaxies in Clusters
Authors: Merritt David , White Simon D. M.
Published: June 2019

Clusters of galaxies are believed to be dominated by dark matter. Some of this matter is presumably bound to galaxies in the form of massive halos, while the rest moves freely in the cluster potential well. The exact fraction of dark matter bound to galaxies is an important datum for models of cluster evolution, since time scales for orbital decay, merging, stripping, etc. are sensitive functions of galaxy mass. In this study we attempt to put a firm upper limit on the amount of dark matter associated with galaxies in clusters, by calculating the response of a galaxy with an initially massive halo to the mean tidal field produced by the overall cluster potential well. If the velocity dispersions of galactic halos are roughly equal to those of luminous galaxies, σg, it is easy to show that the truncated mass of a spherical galaxy orbiting near the center of a cluster is roughly mg ≈ G−1σg3σc−1Rc ≈ 4 × 1011M⊙, where σc and Rc are the cluster velocity dispersion and core radius. The precise value of mg must depend on the orbital geometry, as well as the number of pericenter passages since cluster formation, among other factors.
Self-Gravitating Polar Ring Models
Authors: Sparke Linda S.
Published: June 2019

In a number of SO galaxies, rings of gas, dust and stars are observed to lie roughly perpendicular to the galactic disc (e.g. Whitmore, these proceedings). The material sometimes forms a fairly broad annulus, and the ring appears nearly flat. Simple estimates suggest that differential precession will destroy a polar ring in much less than a Hubble time, implying that the observed structures have been formed only recently. It is then surprising that some of them are so regular, unless something acts to prevent their disruption.
Possible Constituents of Halos
Authors: Rees Martin J.
Published: June 2019

There still seem to be three serious contenders for the dark matter in galactic halos and groups of galaxies: (i) very low mass stars, (ii) black hole remnants of very massive stars or (iii) some species of particle (e.g. axions, photinos, etc.) surviving from the big bang. There are genuine prospects of detecting individual objects in all three of these categories, and thereby narrowing down the present range of options. If the Universe has the critical density (Ω = 1), rather than the lower value (Ω = 0.1–0.2) inferred from dynamical evidence, then the galaxies must be more clustered than the overall distribution even on scales 10–20 Mpc. “Biased” galaxy formation could account for this.
A fiber-optic three-channel photometer for simultaneous UBVRI measurements - improved design and new results
Authors: Barwig H. , Schoembs R.
Published: June 2019

A modern photometer designed for variable star observation should meet the following specifications: 1. Simultaneous measurements of object, comparison star and sky in order to allow compensation of changing atmospheric transparency and background radiation. 2. Simultaneous multicolor measurements of each channel yielding high efficiency and accurate colors. 3. Coverage of a large wavelength region (U-I) with high time resolution. A photometer, fitting these requirements has been designed at the Universitäts-Sternwarte München. In principle light from three sources in the focal plane of a telescope is guided through optical fibers to three spectrographs, each splitting the incoming signal into five wavelength regions. The resulting 15 output channels are linked to photon counting detectors. Their signals finally are processed in a microcomputer.
A twin reflecting astrograph
Authors: Tomita K. , Takahashi K.
Published: June 2019

A newly developed catadioptric optical system and a modified york-type equatorial mounting were designed and constructed. This telescope will be installed at Saipan Island for observing Comet Halley in Feb.-Apr. 1986.
Contact binaries
Authors: Ruciński S.M.
Published: June 2019

The most promising mechanism for the formation of contact binaries involves the orbital angular momentum loss (AML) and the resulting orbital decay of detached but close synchronized binaries. The efficiency of magnetic wind braking should abruptly decrease upon formation of a contact binary because of the transformation into a system of earlier spectral type and (possibly) of longer orbital period. The new primary of the contact system should have convective zone thinner than indicated by the surface temperature of the common envelope. The decrease in the coronal (X-rays and radio) activity of contact binaries, which is indeed observed, is used as an agrument that the AML efficiency in contact is relatively low and that the contact stage is considerably prolonged relative to adjacent stages. This small modification to the AML models is capable of explaining why many different contact binaries are observed in old systems like NGC188. The AML evolution is not the only mechanism leading to formation of contact binaries; some of them may have originated via Algol-like evolution. Thus, the observed contact binaries are probably a mixture of systems formed in different ways.
EX Hydrae timing data
Authors: Hill K. M. , Sharma D. P. , Watson R. D.
Published: June 2019

The 98 min eclipsing cataclysmic variable EX Hya possesses a strong 67 min modulation in its light. This has led to a discussion of EX Hya in the context of intermediate polar variables. The observed P/Ṗ of the 67 min modulation provides a useful constraint on EX Hya models. Here we report additional timing data obtained over the interval 1982 to 1985 which bears on this matter.
Spectroscopic observations of visual double stars
Authors: Batten A. H.
Published: June 2019

Observations of visual binaries made with the 1.2-m telescope and coudé spectrograph at Victoria are described, with particular emphasis on their value as tests of evolutionary calculations.
Temperature and brightness variations on Betelgeuse
Authors: Gaustad John E.
Published: June 2019

Changes in Ti0 band strengths correlate well with the brightness changes of α Orionis, thus supporting the hypothesis of Schwarzschild that the irregular luminosity variations of red giants are due to temperature changes in a few extremely large convective elements on their surface.
Absorption Spectrum of Atomic Chlorine 95.0 nm to 61.0 nm
Authors: Parkinson W. H. , Cantú A.M.
Published: June 2019

The experimental study of atomic chlorine absorption spectra using a flash-pyrolysis system and a 2-m normal incidence spectrograph in the wavelength region 95 nm to 61 nm has produced photoabsorption cross sections, wavelength measurements, and line series identification involving the 3P, 1D and 1S limits. Absorption spectra originating from both levels ( and ) of the ground state have been produced by this method.
A 28kHz-Resolution Acousto-Optic Spectrometer
Authors: Wang J-S. , Robinson B.J. , Huang G-C. , Otrupcek R.E.
Published: June 2019

A 28kHz resolution acousto-optic spectrometer has been established. The modulator is a TeO2 cell with off-axis acoustic slow shear wave. The convolution between the profiles of the modulator and the photodiode array was considered. Its velocity resolution is 0.07 kms−1 for 115 GHz CO molecular lines. The test observations were made by association with the 4-m mm-wave telescope in Australia. Some features of the CO lines in dark clouds have been seen more in detail.
Radio and Millimetre Observations of Larger Molecules
Authors: Avery L. W.
Published: June 2019

The number of known interstellar molecules has increased steadily since 1970 and stands presently at 68. of the molecules discovered in recent years more than half contain three or more heavy elements.

The number of sources where HC5N or HC3N has been detected now includes 21 dark clouds, four circumstellar shells, two bipolar nebulae, the line of sight to the Cas A supernova remnant, and possibly a comet. the more abundant large molecules are useful diagnostic probes, and preliminary statistical equilibrium calculations of the widespread new ring, C3H2, are presented which indicate its usefulness as an indicator of H2 density.
Theoretical Studies of Interstellar Isomers
Authors: DeFrees D. J.
Published: June 2019

Both observational and theoretical studies of molecular cloud chemistry are hindered by many difficulties which are partially circumvented by studying the relative abundances of isomers synthesized from a common set of chemical precursors. Theoretical studies aimed at understanding interstellar abundance ratios for the isomers HCN/HNC, HCO+/HOC+, CH3CN/CH3NC, and C3H2 have been performed.
Chemistry in Shocked Interstellar Gas
Authors: Mitchell George F.
Published: June 2019

In its passage through the interstellar gas, a shock imposes massive and irreversible changes on the chemical composition of the gas. The synthesis of molecules from atoms and atomic ions can be highly efficient behind non-dissociative (i.e. slow) shocks. Results of kinetic calculations behind non-dissociative shocks are reviewed here, with emphasis given to the dependence of the postshock molecular composition on initial cloud properties. It is shown that a dense cloud shock can convert essentially all neutral atoms into various molecules. Even in diffuse and unshielded regions, a variety of molecules can attain a high abundance behind shocks. The suggestion that the widespread diffuse cloud species CH+ is shock synthesized is critically examined in the light of new calculations.
Infrared Observations of Circumstellar Molecules
Authors: Betz Albert
Published: June 2019

This review presents an updated listing of infrared observations of circumstellar molecules. The compendium is restricted to the more abundant species with infrared spectra accessible to groundbased observations. No analysis is offered on the chemical importance of a particular species, and no attempt is made to correlate the infrared work with the much larger body of data available from radio frequency observations. Some discussions of these topics may be found in the more comprehensive reviews listed below. The observations described here include both the successful and the unrewarded efforts. Often the negative results from attempted observations are not widely disseminated, even though such results can sometimes be of significant theoretical value. Discussions of infrared stellar and circumstellar spectroscopy from other vantage points may be found in the following reviews. in 1979 Merrill and Ridgway surveyed the contributions of infrared spectroscopy to studies of stellar photospheres and the near circumstellar environment. The following year Zuckerman (1980) summarized the current state of knowledge on circumstellar molecular clouds with attention given to both infrared and microwave observations. Ridgway and Keady (1981) subsequently noted the importance of infrared spectroscopy for studies of circumstellar gas and dust in the star IRC + 10216. in 1983 Hinkle reviewed the high-resolution spectroscopy of late-type circumstellar shells in general but emphasized chemistry and kinematics. Finally, in the proceedings of the 1984 UCLA meeting on mass-loss, Omont (1985) reviewed the physical and chemical structure of circumstellar envelopes and IRC + 10216 in particular, and Wannier (1985) discussed the significance of infrared spectroscopy for studies of mass-loss in late-type stars.
Chemico-Physical Models of Cometary Atmospheres
Authors: Huebner W. F. , Keady J. J. , Boice D. C. , Schmidt H. U. , Wegmann R.
Published: June 2019

Sublimation (vaporization) of the icy component of a cometary nucleus determines the initial composition of the coma gas as it streams outward and escapes. Photolytic reactions in the inner coma, escape of fast, light species such as atomic and molecular hydrogen, and solar wind interaction in the outer coma alter the chemical composition and the physical nature of the coma gas. Models that describe these interactions must include (1) chemical kinetics, (2) coma energy balance, (3) multifluid flow for the rapidly escaping light components, the heavier bulk fluid, and the plasma with separate temperatures for electrons and the remainder of the gas, (4) transition from a collision dominated inner region to free molecular flow of neutrals in the outer region, (5) pickup of cometary ions by the solar wind, (6) counter and cross streaming of neutrals with respect to the plasma which outside of the contact surface also contains solar wind ions, and (7) magnetic fields carried by the solar wind. Progress on such models is described and results including velocity, temperature, and number density profiles for important chemical species are presented and compared with observations.
Investigation of the Spectra of Some Seyfert Galaxies
Authors: Denisjuk E.K.
Published: June 2019

The real and imaginary changes of shapes of emission lines in spectra of two Seyfert galaxies NGC1068 and MRK79 are examined.