bluuebunny/crossref_metadata_2025 huggingface dataset:
II. — Chili
Authors: Stock J.
Published: July 2016

I believe it is very difficult to make any recommendations or give any advice for site survey expeditions except of a very general nature. When you start out anew, then, as Dr. Scorer has already stressed very strongly, the first thing you have to do is to contact the meteorological office or the local meteorologist. There is no need to go into detail for I think you all realize that the statistics presented by the weather bureau do not serve our purpose. They are made for a different purpose than ours, and you will always have to go back to the original records and pull out from them the data that may be useful. Suppose you have done this, and you have located either on a world-wide scale the country that is the most promising, or within the country the most promising place as far as cloudiness is concerned. Then what are the next steps ?
Space distribution of 156 galactic star clusters and of 61 HII regions
Authors: Becker W.
Published: July 2016

The galactic star clusters are today the only objects whose individual distances and ages can be determined rather precisely. Therefore the space distribution as a function of time can be studied. In case they form a spiral structure, the lifetime of such a structure can be studied too.
The Scorpio–Centaurus association
Authors: Blaauw A.
Published: July 2016

The Scorpio–Centaurus association extends from about lII=356°, bII=+20° towards lower longitudes over about 90° of the southern sky. Between lII=312 and 356° it is located between latitudes +10 and +25°, and appears well detached from the more distant B-star population at lower latitudes. At longitudes below 312° it approaches and crosses the galactic plane and is seen projected against the general low latitude B-star population from which it is more difficult to separate. These features are clearly brought out by Figures 5 and 6 of the author's thesis (1946) and had been recognized earlier by others (e.g. Kapteyn 1914).
The hydrogen lines as luminosity criteria in early-type stars
Authors: Graham J. A.
Published: July 2016

In this short paper, the calibration procedure for the absolute magnitudes derived from the Hβ indices will be discussed. These Hβ indices have been measured for the distant OB-type stars in our studies of galactic structure and are discussed in the paper by Bok which is found elsewhere in this volume (Paper 36).
Large-scale structure and kinematics of the Galactic System
Authors: Lindblad B.
Published: July 2016

It is, I believe, of fundamental importance to find out how far the structure and motions in the galaxies can be explained by gravitational theory. This does not deny that hydrodynamic and electromagnetic forces may play an important part. The special point which I have in mind is the possibility, from the standpoint of gravitational theory, for the spiral structure to be a kind of quasi-steady state of comparatively long lifetime.
Non-circular motions in the galaxy as exhibited by very young stars
Authors: Weaver H. F.
Published: July 2016

I. Expansion of the Gaseous and Stellar Components of the Galaxy

If the gaseous component of the Galaxy is expanding as observed by Rougoor and Oort in the centre of the Galaxy and as postulated by Kerr in his early interpretation of spiral structure, the expansion must represent a phenomenon of fundamental importance in the Galaxy which has, in all probability, been operative for a significant fraction of the age of the Galaxy. Presumably, very young stars formed from this gas and having ages less than 1 % of the age of the Galaxy might be expected to retain in their motions the general character of the large-scale expansion of the gas from which they originated.
A high-resolution study of M31
Authors: Burke B. F. , Turner K. C. , Tuve M. A.
Published: July 2016

The great nebula in Andromeda, M31, is a particularly interesting external galaxy, since it is a giant spiral system, presumably much like our own Galaxy, and is close enough to be resolved with existing radio telescopes. During parts of November 1962, and from December 5, 1962, to January 20, 1963, the 300-foot transit telescope of the N.R.A.O. at Green Bank, W. Va., was used in conjunction with the Carnegie multichannel H-line spectrograph to study M31. The following is a preliminary account of these first observations.
Large HI clouds in the Galaxy
Authors: McGee R. X.
Published: July 2016

van de Hulst (1958), in giving representative sizes of the structural details of the interstellar medium, lists the dimensions of a typical cloud, seen in 21-cm emission, as 20–70 pc but warns that we should not be surprised to find different “sizes of interstellar clouds” determined from different sets of data.
A large high velocity cloud at lII = 41°, bII = −15°
Authors: Oort J. H.
Published: July 2016

In a study made by Miss Gail Smith at Leiden a cloud was found with a rather exceptional velocity and a large velocity spread. The cloud is elongated, with a ratio of length to breadth of about 3 : 1. Its length is about 10°. The average velocity relative to the local standard of rest is +90 km/sec; the width of the profiles is considerable, corresponding to a halfwidth of about 30 km/sec. The mass can be estimated only if we know the distance. Taking 200 pc as a reasonable estimate of the minimum distance of the cloud the minimum mass is about 200 solar masses. The computed mass varies as the square of the distance.
Radial velocities as a guide to spiral structure
Authors: Thackeray A. D.
Published: July 2016

Four main methods of delineating spiral structure in the Galaxy have been developed in the past 10 years.
On the comparison of spiral structure as delineated by gas and by stars
Authors: Weaver H. F.
Published: July 2016

In an earlier article* it was pointed out that the galactic radial motions ΔE (R, l) of the very young stars did not show the uniformity of motion to be expected from a smooth regular expansion of the Galaxy. Instead, the very young stars were found to show large-scale regional peculiar motions; these regional peculiar motions are displayed in Figure 1. In addition to regional peculiar motions and the space distribution of stars, Figure 1 also shows the spiral structure delineated by neutral hydrogen gas. As is customary in such diagrams, the space distribution of gas and the space distribution of the stars are not in good agreement. As various investigators have mentioned, stars and gas appear to define different spiral arms. However, such a conclusion is not warranted by data such as those employed in construction of Figure 1. In Figure 1 (as is invariably the case in earlier published diagrams of the same sort) two distance scales have been employed in the construction of the diagram. The distances of the stars have been derived from photometric data; the distances of concentrations of neutral hydrogen gas have been derived from measured hydrogen gas radial velocities and a galactic rotation curve. It should therefore come as no surprise if there are disagreements between hydrogen spiral arms and star spiral arms. Any regional peculiar motion of a gas concentration directly becomes an error in the inferred distance of the gas concentration.
An infrared survey of the Southern Milky Way
Authors: Westerlund B. E.
Published: July 2016

The determination by optical means of the galactic structure at great distances from the Sun is becoming more and more important. Most optical investigations, using ordinary techniques — objective-prism survey in the blue spectral region + UBV photometry — do not reach very far out owing to the heavy obscuration in most directions in the galactic plane. Only a few very luminous OB stars and some rare supergiants have been identified in some selected regions at distances exceeding 4 kpc.
Reconnaissance d'etoiles appartenant au Grand Nuage de Magellan a l'aide d'un prisme objectif a champ normal
Authors: Duflot M. , Duflot A. , Fehrenbach C.
Published: July 2016

La méthode de mesure des vitesses radiales au prisme objectif à champ normal que nous employons à l'Observatoire de Haute Provence depuis de nombreuses années (Fehrenbach 1947, 1948, 1955) est la méthode idéale pour la recherche des étoiles de grande luminosité, membres des Grand et Petit Nuages de Magellan.
The surface distribution clusters, planetary nebulae, supergiant M stars, and carbon stars in the Large Magellanic Cloud
Authors: Westerlund B. E.
Published: July 2016

Some years ago the plates used for the extended Uppsala–Mount Stromlo Atlas of the Magellanic Clouds were searched for clusters in order to compare the optical extension of the Large Cloud with the one defined by the radio-astronomical observations of neutral hydrogen. Slightly over 150 clusters were identified and good agreement between the radio and optical boundaries was noted (Westerlund, unpublished data).
A cluster of intermediate age in the Large Magellanic Cloud
Authors: Woolley Richard
Published: July 2016

Some years ago (1960) I discussed the HR diagram of the variable star field investigated at Herstmonceux as the result of Drs. Sandage and Eggen's visit to Pretoria, and found colour-luminosity arrays showing mainly very blue giant stars; and later (1961) I suggested that a second and older population could be seen in the same area of the LMC, showing a rather different x,y distribution. Recently Miss Epps has assisted me to make further investigations into the matter. We are now discussing stars fainter than V = 14 · 5 and therefore too faint for us to determine their proper motions. In order to get rid of foreground stars which obscure the HR diagram we have had to make use of the x, y distribution to discriminate between LMC members and foreground stars. Firstly, we examined an open cluster which appears as a faint object on the 74-inch Pretoria plates. It is away from the main lane occupied by the bright blue objects, and its appearance on the B and V plates showed it not to be excessively blue. On a Radcliffe plate (74 in. stopped to 44 in.) with an exposure of 20 min, 29 stars can be seen within a circle of diameter of 1′ of arc. We have been able to determine V accurately for only 15 of these stars, one of which proved to be a variable of period 4–75 days. The HR diagram shows a gap between B – V = 0 · 2 and B – V = 1 · 0, the variable being in this gap. It is comparable with those of NGC 129, NGC 2287, and NGC 6067, and, by analogy with these objects, the open cluster now described probably has an age of about 108 years. The object is of course very different from the young or blue (but tight) cluster NGC 1818 not far away from it.
Energy distribution in globular star clusters
Authors: Aller L. H. , Faulkner D. J.
Published: July 2016

The present investigation is concerned with the energy distributions in globular clusters. In a sense, energy-distribution measurements are comparable with multi-colour photometry. The chief advantage is that narrower band-passes may be used and the entire spectrum traced, whereas in multi-colour photometry one is limited to effective wavelengths determined by the filter and a rather broad band-pass. On the other hand, broad band-pass photometry often permits one to cover a broader spectral range, and to work much faster. Since the time required for a single observation is much shorter, the observer is less at the mercy of the sky transparency. Hence a greater accuracy can be obtained.
Short-period variables in the Magellanic Clouds
Authors: Thackeray A. D.
Published: July 2016

Our knowledge of short-period variables in the Magellanic Clouds remains rather meagre despite the considerable effort that has been put into discovering them. Original failures to detect RR Lyrae variables at the expected magnitude of 17 · 5 led to a temporary belief that perhaps the Clouds contained virtually no Population II. However, the Radcliffe discoveries of RR Lyrae variables in the globular clusters NGC 121 (3), 1466 (44), 1978 (2), and 2257 (17 + 8), put the existence of a Population II component in both Clouds beyond doubt. Moreover, the published light curves and periods of variables in NGC 121 (Thackeray 1958) and NGC 2257 (Alexander 1960) showed the typical characteristics of Bailey types a, b, and c. Thus the comparison, so far as it goes, between the Population II of the Magellanic Clouds and the Galaxy shows no outstanding difference.
Multivariate analysis as a tool in spectral classification
Authors: Jones D. H. P.
Published: July 2016

1.Multivariate analysis.Suppose that one is attempting to set up a classification scheme for a set ofnstars and thatpparameters have been estimated on each plate. The estimates can be arranged in ap×narraywhere each column denotes an individual star and each row an individual parameter estimated. Consider first the simple case where all the parameters are linearly interrelated. Two stars will suffice to calculate the coefficients and subsequently it will be sufficient to specify the first parameter for any star, the rest being uniquely implied. Thus the stars can be placed on a one-dimensional sequence. Geometrically this simple case is that ofnpoints inpspace, all collinear; where one co-ordinate serves to fix the rest and the points are uniquely ordered.
Chromospheric activity as a function of age in main-sequence stars
Authors: Wilson O. C. , Skumanich A.
Published: July 2016

Evidence previously presented by one of the authors (1) suggests strongly that chromospheric activity decreases with age in main sequence stars. This tentative conclusion rests principally upon a comparison of the members of large clusters (Hyades, Praesepe, Pleiades) with non-cluster objects in the general field, including the Sun. It is at least conceivable, however, that cluster and non-cluster stars might differ in some fundamental fashion which could influence the degree of chromospheric activity, and that the observed differences in chromospheric activity would then be attributable to the circumstances of stellar origin rather than to age.
Factors influencing the quality of objective-prism spectra
Authors: Hardie R. H.
Published: July 2016

The definition and clarity of spectral features in objective-prism spectra are determined largely by the telescope's image quality and the seeing conditions. Over the past 3 years, a systematic attempt has been carried out to identify and minimize all relevant factors which would tend to limit the image quality of spectra taken with the Seyfert 24-inch telescope in the Baker Corrector-Reflector arrangement. Both the inherent image quality and the seeing conditions have been brought up to a high degree of perfection.
A comparison of the classification systems of luminous stars in the northern Milky Way II and IV, for stars assigned two-dimensional spectral types from objective-prism plates
Authors: Stephenson C. B.
Published: July 2016

For some years a survey for early-type luminous stars in the northern Milky Way has been underway at the Warner and Swasey Observatory and the Hamburg Observatory, as a joint project by the two institutions (1). With the aid of ultraviolet-transmitting objective prisms (Schott UBK7 glass), it has been possible at both institutions to recognize OB stars at a dispersion of about 600Å/mm. Moreover, the appearance of the Balmer discontinuity at low dispersion affords a valuable aid to two-dimensional classification of stars of late B to late F types (2, 3). These two-dimensional classifications, which are based essentially upon the appearance of the continuum (especially the Balmer discontinuity), the hydrogen lines, the K line, and the G band, are assigned in the MK classification nomenclature since they are well correlated with classifications made by means of the real MK classification criteria. The quality of the correlation depends upon location in the HR diagram, but the random probable error appears to be upward of one MK luminosity class and about a quarter of a full letter division in temperature class, except that luminosity class IV is nowhere well distinguished from class V, and class Iab is not really well distinguished from Ia and Ib.

The present Cleveland system of assigning two-dimensional spectral types to stars from ultraviolet-included objective-prism plates tends to assign lower luminosities than those of the LS II (–LS I?) system. This fact alone accounts for certainly most of the difference between the numbers of stars assigned two-dimensional spectral types in LS II and in LS IV. The origin of this systematic difference of over a luminosity class is not well explained, but the difference is hardly alarming. The numbers of OB stars in the two catalogues are quite comparable and this is consistent with the fact that no classification system difference for OB stars is known to exist between these two catalogues.

Slit spectrograms so far available support the belief that LS IV agrees better in the mean with the MK system than does LS II, though LS IV may also be slightly overluminous in the mean. There is one factor always tending to confuse the transformation from this objective-prism system to MK spectral types: stars having abnormally strong Balmer discontinuities will usually be included in our catalogues with some kind of MK classification, While those with abnormally weak Balmer discontinuities will more often be excluded or assigned to the OB group. This problem is by no means so serious as to detract significantly from the desirability of making objective-prism surveys that pay special heed to the Balmer discontinuity.
Narrow-band photometry at the Cambridge Observatories
Authors: Redman R. O.
Published: July 2016

Narrow-band photoelectric photometry has been carried on at the Cambridge Observatories for 6 or 7 years, using a variety of spectrometers at the coudé focus of the 36-inch reflector. Measurements have been made of the Hαand Hγlines in O and B stars; the diffuse interstellar bands at 4430Å and 6185Å; and of a number of Fraunhofer lines to study luminescence on the Moon. But the greatest effort has gone into measuring numerous features of K-type spectra and these measurements are the subject of this talk, which should be regarded as a progress report, since observations are still being made and a good deal more analysis of the results is still required. The observational procedure has been described in published papers.
Statistical analysis of classification
Authors: Deeming T. J.
Published: July 2016

If we make a set of measurements, such as narrow-band or multicolour photo-electric measurements, which are designed to improve a scheme of classification, and in particular if they are designed to extend the number of dimensions of classification, i.e. the number of classification parameters, then some important problems of analytical procedure arise. First, it is important not to reproduce the errors of the classification scheme which we are trying to improve. Second, when trying to extend the number of dimensions of classification we have little or nothing with which to test the validity of the new parameters.

Problems similar to these have occurred in other areas of scientific research (notably psychology and education) and the branch of Statistics called Multivariate Analysis has been developed to deal with them. The techniques of this subject are largely unknown to astronomers, but, if carefully applied, they should at the very least ensure that the astronomer gets the maximum amount of information out of his data and does not waste his time looking for information which is not there. More optimistically, these techniques are potentially capable of indicating the number of classification parameters necessary and giving specific formulas for computing them, as well as pinpointing those particular measurements which are most crucial for determining the classification parameters.
Potential improvements in photometric accuracy
Authors: Hardie R. H.
Published: July 2016

Photometric methods and techniques have reached a point at which a high degree of reliability can be achieved in principle. In actual practice, good photometric accuracy (in transfer work) can be characterized by accidental errors of the order of 0·01 to 0·02 magnitude and systematic errors less than 0·01 magnitude. The chief factors requiring critical attention for high-accuracy photometry (apart from uncompromising instrumental excellence) are: (i) thorough matching of the natural to the standard system (1), (ii) thorough calibration of the residual differences between the natural and standard systems (transformations and color equations), and (iii) thorough allowance for extinction effects, including their color dependences. These requirements are demanded no less in photographic than in photo-electric work if highly dependable and reliable results are sought.
Multiple colorimetry of the Sun
Authors: Kron G. E.
Published: July 2016

In spite of the importance of knowing the color of the Sun on a modern standard photo-electric system, only two efforts have been made during recent times to measure this quantity. These are by Stebbins and Kron (1) who measured the Sun on the six-color system of Stebbins and Whitford, and by Louis Gallouët (2) who measured the Sun on theUBVsystem of Johnson and Morgan. Stebbins and Kron compared the light from the Sun after it had been dimmed with a special “reducing” device with the light from a tungsten ribbon filament standard lamp, which, in turn, had been compared with the light of distant stars. Gallouët, on the other hand, measured both the Sun and stars by means of an extremely ingenious optical instrument that acted as a light gatherer when used on the distant stars, and as a light reducer when used in its inverted optical sense on the Sun. Gallouët also measured the magnitude of the Sun, as well as the color and magnitude of the full Moon.
Seven-colour photometry at the Geneva Observatory
Authors: Golay M.
Published: July 2016

During the last 5 years, we have developed a seven-colour photometry at the Geneva Observatory. Our multicolour photo-electric system is of a wide-band type; the bandwidth being about 500Å for four filters. The three others are similar to theUBVsystem. In Table 1 we give the filter combinations used in our photometry (1).
List of spectrophotometric standards in use at the Institut d'Astrophysique of Paris
Authors: Divan L. , Chalonge D.
Published: July 2016

The stars of Table 1 have been accurately related to each other over the spectral range 6100–3150Å, and the values of logare given in Table 2. Among them isαLyr for which an absolute energy distribution has been adopted by Code. A new absolute calibration for the stars of Table 1, entirely independent of that ofαLyr, is being completed in Paris.
A spectral survey of southern Milky Way regions
Authors: Lodén L. O.
Published: July 2016

A great spectral survey of the southern Milky Way, initially planned by B. Lindblad, is being carried out at the Stockholm Observatory since 1956. The observations have been performed at the Boyden Observatory in South Africa. The purpose of the investigation is in the first instance an extension and a completing of present lists of high-luminosity stars, stars of rare spectral types, galactic clusters, associations, and nebulae for the southern hemisphere. Within the framework of the principal project a series of partial investigations are to be performed. To a large extent the present programme will also constitute a preparation for continued work at the European Southern Observatory in Chile.
Three-colour photometry of faint stars in galactic and high latitude fields
Authors: Becker W.
Published: July 2016

The classification which is called “Three-Colour-Photometry” belongs to a group of classifications which are developed for extended applications. One of the proper fields are the faint stars, far below the limit of spectral classification. Some years ago we started a programme of three-colour-photometry in small fields at the galactic Equator and at higher latitudes. I would like to show you some observational results which, as far as I can see, illustrate in a convincing way the efficiency of the method in this particular field of application.
M stars in the region of the Pleiades
Authors: McCarthy M. F. , Treanor P. J.
Published: July 2016

An objective-prism survey in the infrared of a region 4°6, square centred on the Pleiades has been made with the Vatican Schmidt and its 2°5 prism in a search for M dwarf members of this cluster. One hundred and twenty-five stars have been classified into four natural groups which correspond to possible dwarfs in the spectral ranges M2-M3, M0-M1, K7-K9 and to non-member field giants of types M0-M4. Provisional blue magnitudes have been obtained by photographic interpolation from photo-electricBmagnitudes of Johnson and Mitchell using an electronic reduction programme by Bertiau which incorporates a sky background correction. Positional, photometric, proper motion and spectral data are provided in a catalogue which is supplemented by individual identification charts. An analysis of the surface distribution, magnitudes and proper motions of the stars indicates that the first three groups contain many cluster members. A select list contains 27 stars mostly fainter thanB= 16 which are considered probable cluster members. The material is discussed in relation to the evolutionary status of the cluster. Our results show that a well-populated main sequence of early M stars is present down toB= 17.
Classification of red stars on Michigan-Mount Wilson southern Hα survey plates
Authors: Henize K. G.
Published: July 2016

During the years 1949–51 the author conducted a survey of the southern sky for stars and nebulae showing emission lines at Hα(1). This survey was conducted at the Lamont-Hussey Observatory of the University of Michigan in Bloemfontein, South Africa, using the 10-inch objective-prism camera designed and constructed at Mount Wilson Observatory specifically for this type of survey. The plates taken with this camera have a dispersion of 450Å/mm at Hαand produce spectra in good definition fromλ5500 toλ6700. The southern survey plates reach a limiting magnitude of 10·5 and cover the entire sky in duplicate south of declination − 25°. Although they are intended primarily for the detection of stars and nebulae showing Hαemission, they also contain much information concerning stars of spectral types M, S, and C.
Spectrophotometry and multicolour photometry at the Royal Observatory, Edinburgh
Authors: Guthrie B. N. G. , Lawrence L. C. , Nandy K. , Pratt N. M. , Reddish V. C.
Published: July 2016

During the past 2 years, the 16, 24, 60-inch Schmidt telescope of the Royal Observatory, Edinburgh, has been used intensively on programmes of multicolour photometry and objective-prism spectrophotometry. The objectives of these programmes are concerned broadly with how, when, and where stars form, and may be classified as follows:

(a) To make a detailed examination of the wavelength dependence of interstellar obscuration, at different distances, and in different galactic longitudes. This will make an essential contribution to the distance determinations in (b) and (c); it is of importance to the study of the physics of interstellar matter and hence also perhaps of star formation; it is a necessary part of the information on which a choice of wavebands for multicolour photometry must be based.

(b) To contribute to the determination of the ages, absolute magnitudes and distances of early-type stars, and the distribution of obscuring matter in selected regions of the Galaxy. This will give information on the rate of formation of stars, as a function of time, in various regions.

(c) To contribute to the determination of the luminosity functions and ages of stars in open clusters and associations.
Some Scattering Problems of Interstellar Grains
Authors: Greenberg J. Mayo
Published: July 2016

Some general effects of size, shape, and material on the scattering properties of small particles are considered with a view to determining their relative importance to interstellar dust interpreatations.
The U, B, V, R, and I Extinctions in Four Areas of the Southern Coalsack
Authors: Tapia S.
Published: July 2016

From star counts the extinctions in five spectral bands were determined for four areas of the Southern Coalsack. The wavelength dependence of the extinction values follows the Whitford curve. Minimum masses for six globules are given.
A Surface Polarization Survey of the Milky Way and the Zodiacal Light
Authors: Staude J. , Wolf K. , Schmidt Th.
Published: July 2016

An elliptical Surface polarimetry of the Night Sky has been carried out at the Boyden Observatory, South Africa. The Milky Way is linearly polarized by p = 1 to 2 % (Figure 1); 11 regions also show a circular polarized light contribution (Table I).

The amounts of circular polarization near v ≈ 0.1 % or less, observed within the Zodiacal Light, are generally not exceeding twice the error of measurement: see Staude and Schmidt (1972). (v > 0 is defined by clockwise rotation, looking against the light source).
Interstellar Circular Polarization and the Composition of Interstellar Dust
Authors: Martin P. G.
Published: July 2016

This paper shows that optical observations of circular polarization produced by aligned interstellar grains could yield valuable information about the grain material. The interstellar medium is known to be linearly dichroic from observations of interstellar linear polarization; many different grain models using a large variety of compositions can be found to reproduce these observations. Since the same aligned grains make the medium linearly birefringent, a small component of circular polarization can result from incident linearly polarized light if the position angle of the linear polarization does not coincide with either principal axis of the medium. Here calculations are presented to demonstrate that the wavelength of the circular polarization is sensitive to the imaginary part of the complex refractive index of the grain material. This provides an opportunity of investigating whether the grains are characteristically dielectric or metallic. Some possible observations are suggested.
A Search for Infrared Polarization in the Galactic Center
Authors: Maihara T. , Okuda H. , Sato S.
Published: July 2016

Observations of infrared polarization have been tried in the galactic center. A preliminary result is that the polarization at K-band (2.2 μ) is less than 5 %, much less than that expected from interstellar polarization.
The Differential Polarization of Starlight as a Function of Distance
Authors: Lloyd Stephen , Harwit Martin O.
Published: July 2016

We have plotted the differential polarization as a function of distance and galactic longitude for 1732 stars between galactic latitudes −5° and +5°. The data were obtained from several published sources. A fairly clearcut distinction is seen between the effects of spiral arms and inter-arm regions indicating that starlight is systematically polarized only when passing through spiral arms.
Polarization of Light by Dust in Galaxies
Authors: Elvius Aina
Published: July 2016

Several galaxies were observed for polarization during April and May 1972. Preliminary results are presented concerning those galaxies where polarization can be expected because of selective extinction or scattering of light by interstellar dust.
A Study of the Distribution of Interstellar Matter
Authors: Lodén Lars Olof
Published: July 2016

As a first step towards an empirical estimation of the minimum size of interstellar dust formation units (clouds etc.) the correlation between angular separation and difference in colour excess has been studied for a selection of close star couples with coinciding magnitude and spectral type. Principally, the result indicates that there is no palpable correlation between the difference in colour excess and the lateral separation of the stars. This and other properties speak in favour of the conception that obscuring matter in the Milky Way is concentrated in extremely small units of high density.
Galactic Dust Distribution in the Solar Neighborhood
Authors: Cahn J. H. , Nosek R.D.
Published: July 2016

Using the Shklovsky-Minkowski-Aller constant mass method of distances to planetary nebulae, a model of the Galactic dust distribution in the vicinity of the Sun has been determined. Distances are determined in part from extinctions derived from radio continuum to Hβ flux ratios for an assumed electron temperature of 7000 K. The distance scale is based on the brightness of planetary nebulae in the Magellanic Clouds (Seaton, 1968).
On the Genetic Relation Between Interstellar Clouds and Dust Clouds
Authors: Shu Frank H.
Published: July 2016

We propose that many of the denser dust clouds represent transient stages between the initiation of gravitational collapse of ordinary interstellar clouds by passage through a spiral galactic shock and the appearance of a stellar association. The interstellar gas is not processed at too rapid a rate (1) because the time spent between galactic shocks is appreciably longer than the free-fall collapse time of a typical dust cloud, and (2) because only a small fraction of the total mass of gas of a given collapsing cloud is converted into stars – the rest is presumably redispersed by various dynamical processes which accompany the formation of massive stars. We note that the residue of atomic hydrogen observed to exist in dark dust clouds is compatible with the interpretation that they are transient objects whose lifetimes are not longer than ~ 107 yr.
Molecular Distributions in Galactic Sources
Authors: Dickel Hélène R.
Published: July 2016

The 4830 MHz absorption line of formaldehyde has been observed in the SNR complex W44 and the H ii region complex W3. The results are presented as maps of apparent optical depth. The formaldehyde is concentrated toward the eastern edge of the shell and reaches a maximum apparent optical depth of 1.5 compared with 0.2 for OH; furthermore the centers of the H2CO and OH concentrations are displaced by about 6′. The velocities of the H2CO and OH agree and both molecular lines have the same velocity gradient across the source.

The H2CO absorption profiles for W3 (IC 1795) exhibit at least two narrow components whose average velocity becomes more negative toward the NE. The greatest optical depth occurs where the optical obscurration is high but not at the position of maximum Av. A general agreement between the velocities of other molecules and the H2CO values is indicated.
Optical Measurements on Solids of Possible Interstellar Importance
Authors: Huffman Donald R. , Stapp James L.
Published: July 2016

Optical constants of olivine – (Mg, Fe)2SiO4 and magnetite – Fe3O4 are presented for the wavelength range from near infrared to far ultraviolet. A feature occurs in the optical constants of olivine at about 1460 Å, but no structure that could give rise to a 2200 Å interstellar feature is found. The most peculiar characteristic of the magnetite results is the large change of optical properties with temperature in the infrared.
Spectroscopic Simulation of Diffuse Interstellar Lines and a Laboratory Model for Interstellar Chemical Synthesis
Authors: Johnson F. M. , Bailey D. T. , Wegner P. A.
Published: July 2016

The interstellar existence of dipyridyl magnesium tetrabenzporphin (I) is supported by the spectroscopic coincidence of laboratory generated and astronomically observed diffuse interstellar lines. A potential route for the synthesis of I in space from molecules which exist or are expected to exist there will be discussed.
Ejection of Grains from Cool Stars
Authors: Wickramasinghe N. C.
Published: July 2016

Dust grains expelled from cool stars are injected into interstellar clouds with typical velocities of ~ 103 km s–1. The interaction of such high-speed grains with gas is discussed. Grains are preferentially stopped within clouds of number density nH ≈ 10–30 cm–3. Collisions of grains with gas atoms could lead to heating and ionization of clouds and to the production of displacement defects in grains.
Cyanoacetylene: New Lines and Sources in the Galaxy
Authors: Morris M. , Palmer Patrick , Turner B. E. , Zuckerman B.
Published: July 2016

Microwave emission from the J = 8 → 7 through the J = 11 → 10 rotational transitions of HC3N has been detected in the directions of Sgr(NH3A), Sgr B2, and Orion A. A map of the J = 8 → 7 emission around Sgr B2 shows that the emitting region extends at least 2′ in galactic longitude and 3′ in galactic latitude. Column densities may be comparable to those of HCN in some sources. This molecule is thus more abundant in the interstellar medium than would be expected from its complexity, and may provide clues to formation processes where it is found.

With a reasonable model for excitation of the rotational levels, we have used the ratio of antenna temperatures of these 2 lines to derive a value for the molecular density in the region where the lines originate. For Sgr B2, this yields NH2 ≈ 106, and for Sgr(NH3A), NH2 ≈ 6 × 104.
Chemical Evolution of Dense Clouds
Authors: Chapelle E. W. , Donn B. D. , Payne W. A. , Stief L. J.
Published: July 2016

Thermal reactions largely determine the chemical evolution of interstellar molecules during various phases associated with the evolution of interstellar clouds. A similar mechanism may be the source of the array of observed polyatomic molecules. If astronomical time scales are comparable to or less than chemical time scales, thermodynamic equilibrium will not be attained. Other factors also affect the validity of thermodynamic calculations of molecular composition. An experimental investigation of thermal reactions in a simplified system is under way. Preliminary results of the HCN–H2 reaction at 1000 K indicate reaction times of several hours. These have been extrapolated to lower temperatures and fitted to models of the primordial solar nebula, proto stars and red giants. In these situations equilibrium would generally not be attained and reaction products would freeze out at temperatures near 700 K or greater.
Low Resolution Spectrum of the Orion Nebula in the 60–300 μ Range
Authors: Swift C. D. , Witteborn F. C. , Erickson E. F. , Caroff L. J. , Augason G. C. , Mord A. J. , Kunz L. W. , Giver L. P.
Published: July 2016

Airborne observations of the Trapezium region of the Orion Nebula in the 60–300 μ range have been made from 13.7 km altitude using a Michelson interferometer with the Rice University 12-in. Flying Infrared Telescope. Fourier analysis of five interferometer scans provided spectra with resolution ranging from 7 cm–1 to 20 cm–1. These spectra were compared with lunar spectra taken with the same instrument at the same altitude to correct for instrumental and atmospheric effects. A weighted combination of these scans provides a low resolution spectrum. The radiation per unit frequency interval at 190 μ was found to be at least 40% of that measured between 75 and 90 μ. Neglecting possible features in the spectrum, its general shape is consistent with a blackbody near 70 K. The resolution is inadequate to resolve spectral lines.
Radiative Transfer in Circumstellar Dust Clouds
Authors: Code A. D.
Published: July 2016

Radiative transfer methods are used to show how and to what extent the usual techniques relating color excess to optical depth through circumstellar material are not applicable.
Spin Evolution of the Progenitors of Binary and Millisecond Pulsars
Authors: Ghosh Pranab
Published: July 2016

In this symposium, I have been given the task of summarizing our current understanding of the evolutionary history of spin periods of the neutron stars that we now see as binary and millisecond pulsars, i.e., recycled pulsars. We believe that a newborn, fast-spinning neutron star (with a rather high magnetic field ∼1011–1013 G) in a binary system first operates as a spin-powered pulsar, subsequently as an accretion-powered pulsar when accretion begins after the pulsar has been spun down adequately, and finally as a spin-powered pulsar for the second time after having been recycled to become a very fast-rotating neutron star (with a rather low magnetic field ∼108–1011 G) (see Ghosh 1994a, b, hereafter G94a, b).
The Ecology of Magnetic Rotators
Authors: Lipunov V.M.
Published: July 2016

A review is given concerning the current state of the theory of evolution of magnetic compact stars. The intrinsic evolution of the magnetized compact star is shown, both theoretically and numerically, to be the decisive factor in explaining observable properties, and in predicting yet unknown properties of high-energy radiation sources in our and other galaxies. The main results are given of recent evolutionary scenario simulations (Scenario Machine) by the Monte-Carlo method.
The Formation and Evolution of Black-Hole Binaries
Authors: Romani Roger W.
Published: July 2016

The presence of accreting black holes (BH) among the X-ray binaries has been recognized for many years. Traditionally, Cyg X-1 and the handful of other candidates have been thought of as cousins of the HMXB neutron star systems. Recent studies of the soft X-ray transients such as A 0620-00 have, however, shown that the dynamical evidence makes these low-mass systems very strong black-hole candidates. Further, analysis of the eventual end-states of various high-mass X-ray binaries suggest that some could end as observable BH-pulsar binaries, although the first such system is yet to be discovered.
Type II Supernovae in Binary Systems
Authors: Joss P.C.
Published: July 2016

The presence of a close binary companion can affect the evolution of a massive star through one or more episodes of mass transfer, or by merger in a common-envelope phase. Monte Carlo calculations indicate that ∼20–35% of all massive supernovae are affected by such processes, and that a substantial fraction of these events will be supernovae of type II. The properties of the progenitor star, the distribution of circumstellar material, the peak supernova luminosity, the shape of the supernova light curve, and other observable features of the supernova event can be affected by prior binary membership. Binary interactions may be the cause of much of the variability among type II supernova light curves. In particular, many of the peculiarities of SN 1987A and SN 1993J may well have resulted from the prior duplicity of the progenitors.
Gravitational Waves from Compact Bodies
Authors: Thorne Kip S.
Published: July 2016

According to general relativity theory, compact concentrations of energy (e.g., neutron stars and black holes) should warp spacetime strongly, and whenever such an energy concentration changes shape, it should create a dynamically changing spacetime warpage that propagates out through the Universe at the speed of light. This propagating warpage is called gravitational radiation — a name that arises from general relativity's description of gravity as a consequence of spacetime warpage.
Periastron Observations of the PSR B1259-63/SS 2883 Binary System
Authors: Johnston Simon
Published: July 2016

PSR B1259-63 is a 47-millisecond pulsar which was discovered in a high frequency survey of the galactic plane (Johnston et al. 1992a) and was subsequently found to be in a highly eccentric orbit with a main-sequence Be star known as SS 2883 (Johnston et al. 1992b). Radio observations of the pulsar led to a phase connected timing solution which predicted the epoch of periastron to be 1994 January 9 (MJD 49361.2); optical observations of the Be star led to a determination of its mass and of the size of its circumstellar disk (Johnston et al. 1994a): the star is of approximate spectral type B1e, with mass 10 M⊙ and radius 6 R⊙. If this mass is correct and the pulsar has a mass of 1.4 M⊙, then the inclination angle of the plane of the orbit with respect to the sky is 35°. This pulsar has an unusually flat radio spectrum compared to most pulsars, which makes it easily detectable up to 8.4 GHz. The narrow pulse permits dispersion and scattering measurements for studying the ionized plasma in the system. Moreover, the pulses are highly linearly polarized and permit determination of the rotation measure (RM), allowing measurements of the magnetic field along the line of sight. The 3.5-yr orbit of the pulsar around its companion thus provides us with an excellent probe of the stellar wind of the Be star over a wide frequency range.
High-Mass X-ray Binaries: Recent Developments
Authors: Nagase F.
Published: July 2016

There are about a dozen extensively investigated high-mass X-ray binaries (HMXBs), including LMC X-4, Cen X-3, 4U 1700-37, SMC X-1, Cyg X-1, and Vela X-1. Bhattacharya & Van den Heuvel (1991) compiled a list of “standard” HMXBs (see table 8 of their review article) and most of them, except for Cyg X-1 and 4U 1700-37, are accreting X-ray pulsars with an early-type or a Be star companion. Cyg X-3 was long considered to be a low-mass X-ray binary (LMXB). It was, however, recently revealed from infrared observations that the companion star has characteristics of a Wolf-Rayet star and it may be a fairly massive helium star (Van Kerkwijk et al. 1992; Van Kerkwijk 1993). I shall review here some recent progress in observational studies of the “standard” HMXBs and Cyg X-3.
ROSAT Observations of Soft X-ray Transients in Quiescence
Authors: Verbunt Frank
Published: July 2016

Four soft X-ray transients, two with a neutron star and two with a black hole, have been detected at quiescence with ROSAT. Blackbody fits to their spectra give temperatures of 160–300 eV, and surface areas of <1 km2. The small surface area suggests that the actual spectrum may be optically thin. The companion star does not contribute significantly to the X-ray luminosity, except perhaps in the case of A 0620-00. From the observation that accretion continues at luminosity levels of ∼1033 erg s−1 it is concluded that the neutron stars in Aql X-1 and Cen X-4 have a weak magnetic field and rotate rather slowly.
Discovery of a New X-ray Transient in Scorpius GRO J1655-40 ≡ X-ray Nova Scorpii 1994
Authors: Paciesas W.S. , Zhang S.N. , Rubin B.C. , Harmon B.A. , Wilson C.A. , Fishman G.J.
Published: July 2016

A bright transient X-ray source, GRO J1655-40 (X-ray Nova Scorpii 1994) was discovered with BATSE (the Burst and Transient Source Experiment) in late July 1994. More recently, the source also became a strong radio emitter, its rise in the radio being approximately anti-correlated with a decline in the hard X-ray intensity. High-resolution radio observations subsequent to this symposium showed evidence for superluminally expanding jets. Since the hard X-ray emission extends to at least 200 keV and we find no evidence of pulsations, we tentatively classify the source as a black-hole candidate. However, its hard X-ray spectrum is unusually steep (power-law photon index α ≃ −3) relative to most other black-hole candidates. In this regard, it resembles GRS 1915+105, the first galactic source to show superluminal radio jets.
Dynamics and Binary (Trans)formation in Globular Clusters
Authors: Hut Piet
Published: July 2016

Globular clusters form ideal laboratories for studying the interactions between stellar evolution and stellar dynamics. In the past, highly exceptional systems such as X-ray binaries and later millisecond pulsars have provided us with useful diagnostic tools. However, the fate of the bulk of the more normal stars has remained less clear. At present, rapid progress is being made in our understanding of the distributions of normal stars and primordial binaries, as well as their most abundant reaction products: blue stragglers and binaries that are produced through exchange encounters with other single stars or binaries. The complexity of the network of exchange reactions is illustrated through some specific examples, such as a formation scenario for the hierarchical triple system containing the millisecond pulsar PSR B1620-26 in M4, the first triple star system ever detected in a globular cluster.
Supersoft X-ray Sources in the LMC
Authors: Cowley A.P. , Schmidtke P.C. , Crampton D. , Hutchings J.B.
Published: July 2016

Data obtained with ROSAT have established the “supersoft” X-ray sources (SSS) as a separate class of objects. Their unique features include temperatures of ∼30 eV and luminosities of ∼1038 erg s−1. Hasinger (1994) has recently summarized the properties of the SSS presently known in the Galaxy and the Magellanic Clouds (cf., Kahabka & Trümper 1995). The six which are thought to be LMC members are listed in Table 1 and discussed individually, based primarily on optical data we have obtained at CTIO.