bluuebunny/crossref_metadata_2025 huggingface dataset:
Elliptic Polarization of Synchrotron Radiation
Authors: Legg M. P. C. , Westfold K. C.
Published: July 2016

Although the synchrotron emission from a single electron moving with an ultrarelativistic velocity βc in a magnetic field B0 is elliptically polarized, the characteristics of the polarization ellipse being determined by the position of the direction of observation n relative to the cone swept out by the direction u of the velocity vector about the direction of B0, the resultant emission from a distribution of such gyrating electrons is, to a first approximation, linearly polarized in the direction perpendicular to the projection of B0 on to the plane transverse to n. The reasons for this are that for a single electron the emission is effectively confined to within a small angular distance O(ξ) of u, where ξ = √ (1 −β2) ≪ 1 and that (i) the fourth Stokes parameter is to this approximation an odd function of the angle ip between n and u at its closest approach, and (ii) the number of electrons passing within equal angular distances ψ = ±O(ξ) are equal. It follows that if ξ is large enough it is possible for the next approximation to the fourth Stokes parameter for a distribution of electrons to be significant, so that the resultant emission is elliptically polarized.
Planetary Modulation of Solar Activity
Authors: Bigg E. K. , Mulhall P. S.
Published: July 2016

It has recently been shown that the planet Mercury exerts a small control on relative sunspot numbers, the degree of control depending on the positions of the other planets.

This paper describes the results of extending the work to include all the planets.

As a working hypothesis we have assumed that gravitational tidal forces induced on the Sun by the planets may modulate solar activity and have accordingly calculated relative equilibrium ‘high tide’ displacements of the solar surface for each day from the positions, masses and distances of the first six planets. Although the tides are very slight, the mass of displaced material is appreciable and varies over the very wide range of nearly 5 to 1.
The Anglo-Australian 150-Inch Telescope
Authors: Bowen E.G.
Published: July 2016

In April of this year agreement was reached between the British and the Australian Governments to build a 150-inch telescope for observations of the southern sky.

The agreement specified that:

(i) the telescope would be built at the Australian National University’s present site at Siding Spring Observatory;

(ii) the expected cost was $11 million and the telescope would be built and operated on a 50-50 basis as between the two Governments;

(iii) the telescope would be virtually a copy of the existing Kitt Peak 150-inch design. This was intended to save the time usually needed for the design of a new telescope and, as we shall see, it might lead to considerable savings in cost.
Preliminary Observations of the Sun at 80 MHz with the Culgoora Radioheliograph
Authors: Kai K. , Mclean D.J. , Payten W. J. , Sheridan K.V. , Wild J.P.
Published: July 2016

This paper describes a preliminary series of observations of the Sun made at a frequency of 80 MHz with the 3 km radioheliograph of the Culgoora Observatory. The instrument records, at one-second intervals, pictures of the solar image in the form of 60 (E-W) × 48 (N-S) points, each separated in angle by half the Rayleigh limit (2’ arc in the zenith). At the time of the present observations the instrument was incomplete in three main respects : (a) the facilities for recording opposite senses of circular polarization were not available; (b) the automatic image compensation for zenith-angle foreshortening was not available—hence the optical disk of the Sun appears elliptical; and (c) the phase and amplitude calibration procedures had not been fully established, resulting in a higher sidelobe level than that specified in the design—the effects are sometimes evident in the pictures as spoke-like brightenings.
The Manganese Star HD 1909
Authors: Buscombe W. , Chambliss C.R. , Kennedy Pamela M.
Published: July 2016

A coudé spectrogram of dispersion 150 µ/Å, exposed at the 74-inch reflector by D. S. Mathewson, reveals very many unusually sharp absorption lines due to ionized metals in the atmosphere of the B9 star HD 1909.
Finite-amplitude Adiabatic Oscillations of Super-massive Stars
Authors: Borght R. Van Der
Published: July 2016

As shown recently by Y. Osaki super-massive stars with mass M < 3.5 × 105M⊙ can, in the absence of rotation, reach the hydrogen-burning main sequence before the onset of general relativistic instability. Such objects are then pulsationally unstable. A considerable simplification is introduced if one considers only very massive stars, for which the relative amplitude of the fundamental mode of oscillation is practically constant. This sets a lower limit of 104M⊙ to the mass that can be considered. The upper limit is also reduced to 2 × 105M⊙ if one neglects the relativistic correction. One necessary step in the study of non-linear oscillations of massive stars is to derive a differential equation for the adiabatic pulsations. The relativistic correction could be taken into account in the following way.
Neutrino-Electron Interactions and Stellar Evolution
Authors: Campbell J.A.
Published: July 2016

A large part of the energy lost from interiors of evolving stars at temperatures greater than about 5 × 108°K is carried away by neutrinos. Three neutrino-producing reactions which have been incorporated in various evolutionary models are the photoneutrino process:

direct annihilation of electron-positron pairs:

and the plasma process:
Frequency Redistribution during Scattering
Authors: Argyros J.D.
Published: July 2016

A photon with frequency in the range v to v + dv travelling in a direction n̂ within the solid angle dΩ is written (v, n̂).

Considering a mass of gas which is stationary relative to an observer and whose atoms are in continuous random thermal motion, then a redistribution function
The Variability of Centaurus XR-2
Authors: Francey R. J. , Fenton A.G. , Harries J.R. , McCracken K. G.
Published: July 2016

This paper presents results from a series of rocket flights which have yielded the first unambiguous evidence for the variability of a cosmic X-ray source. The evidence rests primarily on three flights, the first two of which were conducted from Woomera by a joint Universities of Adelaide and Tasmania (UAT) team, and the third from Hawaii by the Lawrence Radiation Laboratories (LRL) of California. Data from two additional flights, one by LRL and the other by the University of Leicester, support this evidence.
Observations of Ionospheric Movements by the Use of a Large Aerial Array
Authors: Briggs B. H.
Published: July 2016

The ionosphere does not behave like a smooth mirror for radio waves, but more like an irregular diffracting screen. When a radio wave is reflected from it, a random diffraction pattern is formed over the ground. Simple arguments can be used to show that this pattern will move over the ground with a velocity which is twice the horizontal velocity of the ionosphere. This phenomenon can be used for the detection of movements taking place in the ionosphere.
Resistive Instabilities and Solar Flares
Authors: Lister G. G.
Published: July 2016

The study of plasma instabilities described by the inclusion of a finite conductivity in the hydromagnetic equations has aroused considerable interest since the initial work of Furth, Killeen and Rosenbluth for a two-dimensional geometry. In particular, the so-called ‘tearing’ mode, which has been observed in laboratory plasmas, has been suggested as a possible source of energy for solar flares.
The f-Numbers of Fe III
Authors: Baker S. C.
Published: July 2016

The present knowledge of atomic spectra is quite impressive but is far from satisfying all needs in fields such as astronomy. The first and second spectra of many elements have been analysed into energy levels but the spectra of the rare earths and many highly ionized atoms are largely unexplored. However the spectra of Fe I, II and III are now fairly well analysed.
The LMC Clusters NGC 2010 and NGC 2136
Authors: Gascoigne S. C. B. , Hearnshaw J. B.
Published: July 2016

Clusters containing cepheids, and especially clusters containing more than one cepheid, provide information on the advanced evolutionary stages of massive stars, and on the factors which influence the period-frequency relations and lifetimes of cepheids. NGC 1866, in the LMC, is already well known in this respect. NGC 2010 was found by Hodge to contain two cepheids. Two more variables have been found in this cluster which, from their magnitudes and colours, are almost certainly cepheids, though we do not yet have periods for them. We noticed also that two known cepheids, HV 2868 and HV 2870, are associated with NGC 2136.
Interstellar: The Galactic Magnetic Field
Authors: Mathewson D. S.
Published: July 2016

Over a period of one year from March 1967, the 24-inch rotatable telescope at Siding Spring Observatory was used to make polarization measurements for about 1400 stars, most of which were within 400 pc of the Sun. It was found that the E vectors of the polarization formed quite definite patterns on the sky which could only be produced if the magnetic field has a helical structure. Results of model-making showed that the magnetic lines of force form tightly wound right-handed helices of pitch angle 7°. They lie on the surface of tubes which have elliptical cross-sections of axial-ratio 3 with semi-major axes parallel to the galactic plane.
A New X-ray Object at High Galactic Latitude
Authors: Barnden L. R. , Francey R. J.
Published: July 2016

This paper presents evidence for the existence of a previously unobserved X-ray source in the constellation Cetus. The astronomical significance of an intense X-ray object located so far from the galactic disk has prompted this preliminary report.
Instrumental and Data Processing: Correction of High-resolution Solar Scans
Authors: Peterson C. E.
Published: July 2016

Correlation radiotelescopes have become increasingly important in the last few years in all types of astronomical observations. These instruments operate by multiplying (correlating) the outputs of two separate aerials in order to provide a composite antenna with a range of aerial spacings and orientations. As a general rule this range of spacings is truncated at both the largest and smallest spacings, the largest spacing being determined by the area available or by the cost of the system, and the lowest spacing by either cross coupling between the multiplying elements (as in the Mills Cross type) or by the geometrical size of the elements (as in the compound interferometer type).
High-Dispersion Spectroscopy and the Interpretation of Stellar Atmospheres
Authors: Aller L. H.
Published: July 2016

The atmosphere of a star presents a real challenge to the astronomer or physicist. We can observe but the thinnest skin of the star; yet from the information obtained therefrom we must deduce the star’s temperature, chemical composition, its rotation (if any), the state of agitation in its outer layers, and eventually the surface gravity, total luminosity, mass, and evolutionary stage.
Non-L.T.E. Analysis of Spectral Lines
Authors: Mugglestone D.
Published: July 2016

At a previous meeting of the Society I well remember Paul Wild saying, in a humorous vein of course, that until recently he had always thought that an H-R diagram was a plot of H against R. It occurs to me that the same kind of vagueness, although perhaps not to the same degree, might be present with astronomers not directly concerned with the theory of stellar atmospheres in regard to ‘L.T.E.’ and ‘Non-L.T.E.’ analysis of spectral lines. In the present paper, I would like to point out some of the important features of non-L.T.E. analysis, to indicate how the basic theory may be developed, and to show what effect this has on the theoretically produced absorption lines. I will make particular reference to the solar atmosphere and here we take the ‘model atmosphere’ approach where all the physical parameters such as gas pressure, electron pressure, temperature etc., are all specified as functions of optical depth.
Radio Evidence for the Propagation of Magnetohydrodynamic Waves along Curved Paths in the Solar Corona
Authors: Smerd S. F.
Published: July 2016

In this paper 80 MHz heliograph observations are described of a remarkable solar outburst on 1969 March 30 initiated by a flare on the invisible hemisphere of the Sun. The event raises several questions of theoretical interest, in particular the implication that the magnetohydrodynamic waves responsible for certain type II bursts must travel along curved paths.
Observations of Centaurus A at 80 MHz
Authors: Lockhart I. A. , Sheridan K. V.
Published: July 2016

We present observations made at 80 MHz with the Culgoora radioheliograph of the compact central components of the radio source Centaurus A, which is associated with the peculiar galaxy NGC 5128.
Variations in the Secular Motions of the Pole
Authors: Abraham H. J. M.
Published: July 2016

The object of this paper is to show that librations of the Earth follow conditions that are prescribed by nutations. The poles of rotation, excitation and inertia are treated as moving within a system that has approximately constant speed and direction relative to the Conventional International Origin. Applied excitations are presumed to cause other excitations, part forming at once and part forming progressively.
Population I Helium Burning Red Giants. Observations
Authors: Cannon R. D.
Published: July 2016

The basic observational evidence for helium-burning red giants in open clusters has been given elsewhere, and I shall give here only a summary and then describe in more detail new results for one cluster, NGC 2477.
Population I Helium Burning Red Giants. Theory
Authors: Faulkner D. J.
Published: July 2016

In the preceding paper, Cannon has outlined the observational evidence for the existence of a distinct concentration of stars near the base of the red giant branch in intermediate-age galactic clusters, which he tentatively identifies with the core helium burning phase of evolution occurring after the helium flash. This paper reports preliminary results of evolutionary calculations to test this identification.

Since the computation of hydrogen shell-burning evolution up the red giant branch is extremely time-consuming, the present calculations have been commenced at the stage immediately following the helium flash. It is assumed that no overall mixing occurs at the flash, so that the composition discontinuity at the hydrogen-burning shell remains sharp. The initial stellar composition was set at (X, Y, Z) = (0.68, 0.30, 0.02), corresponding to Population I material.
Determination of Interatomic Potentials
Authors: Dyne R. J.
Published: July 2016

In the atmosphere of the Sun, most spectral lines are broadened by collisions between the radiating atom and neutral particles. The interaction between two atoms is usually represented by the multipole expansion of the total interaction potential. For two neutral atoms, the first non-zero term in this expansion arises from induced dipole-induced dipole forces and is proportional to r-6. Most calculations of broadening due to neutral atoms have assumed this van der Waals interaction, V(r) = —C6 r-6, between the atoms. Such an assumption is only valid if the interatomic separation is much greater than the sum of the radii of the two atoms so that no overlap occurs and only the leading term of the multipole expansion need be considered. However, in fitting the wings of solar line profiles, O’Mara found that the value of the van der Waals constant, C6, had to be increased by up to a factor of ten in order to obtain agreement between theoretical and observed profiles.
Broadening of the Solar Sodium D-Lines by Atomic Hydrogen
Authors: Mcnamara L. F.
Published: July 2016

It is well known that the wings of the solar sodium D-lines cannot be predicted successfully using present line-broadening theories and elemental abundances derived from an equivalent-width analysis of the weak lines. By far the most important cause of broadening of the D-lines is collision broadening by neutral hydrogen.
A Coronal Disturbance Observed Simultaneously with a White-Light Coronameter and the 80 MHz Culgoora Radioheliograph
Authors: Hansen R. T. , Garcia C. J. , Grognard R. J.-M. , Sheridan K. V.
Published: July 2016

Observations on 1970 August 11 and 12 at Mauna Loa (Hawaii) of the white-light corona revealed a rare solar event in the form of a short-lived coronal brightening off the eastern limb of the Sun. The intensity of this region, as measured at a distance ρ = 1.5 (where ρ = R/R⊙), more than doubled over a period of five hours and then fell very abruptly (~10 min) to below its initial brightness. A complex radio event in the same region was observed simultaneously with the 80 MHz radioheliograph at Culgoora (Australia). Associations between the optical and radio events will be described and the physical implications briefly discussed.
Evolution of a Jet-like Structure in the Late Phase of a Complex Solar Outburst
Authors: Riddle A. C. , Sheridan K. V.
Published: July 2016

A new feature in the form of a jet formed by close juxtaposition of a number of highly polarized, separately resolved 80 MHz sources was observed as the late phase of a very complex outburst on 1971 January 25. We present here a source model which, we think, can explain the observed source properties. The early phase, also complex and involving numerous moving sources, will be described first.
Coronal Broadening of the Crab Nebula 1969-71: Interpretation
Authors: Dennison P. A. , Blesing R. G.
Published: July 2016

In the preceding paper, observations of the coronal broadening of the Crab Nebula during 1969-71 were described. The basic parameters, radial and tangential broadening, and their relation to previous work were discussed. Whereas previous observations have utilized two or three interferometers only, so that the degree of broadening along any particular axis could only be obtained under the assumption of a particular form (e.g. Gaussian) for the angular power spectrum, the present work has enabled complete sampling of the two-dimensional brightness distribution of the broadened source. It is therefore possible, and of considerable interest, to compare the observed distributions to those computed on the basis of various theoretical models for the scattering process.
The Development of a Black Hole—The Oppenheimer-Snyder Dust Cloud
Authors: Szekeres P.
Published: July 2016

When a star of mass ≳ 2M⊙ collapses there does not appear to exist any physical mechanism to prevent total gravitational collapse, unless in some miraculous way the star always manages to blow off enough mass for it to settle down into a stable neutron star or white dwarf configuration. General relativity is needed in order to handle the ultimate situation, and the theory predicts a critical radius ρ = 2m (in units such that G = c = 1) at which the coordinates in the Schwarzschild solution

become invalid.
Pairs of Spherical Mirrors as Prime Focus Correctors for the Anglo-Australian Telescope
Authors: Rumsey N. J.
Published: July 2016

Last year I described pairs of spherical mirrors that remove the coma and astigmatism in the image formed by a paraboloid mirror and leave the spherical aberration corrected. The investigation can be extended to deal with other shapes of primary mirror, for example the hyperboloid primary of the Anglo-Australian Telescope. The algebraic analysis becomes more complicated than for a paraboloid; but it still has the feature that at an early stage a cubic equation has to be solved, each real root of which gives rise to a second cubic. Thus in principle the mathematics could lead to nine solutions. However, it again turns out that not all the roots are real; and even for the real roots not all the solutions are physically useful, because in some cases the final image is virtual, and in others the tertiary mirror lies behind the secondary where light can not reach it. When the primary is a paraboloid, there are three useable solutions all with the property that the field corrector (consisting of the pair of spherical mirrors) can simply be scaled up or down at the user’s pleasure according to the diameter of the field he wishes to photograph. When the primary is of any other shape this is no longer possible.
Galactic Spiral Arms and Evolution
Authors: Piddington J. H.
Published: July 2016

It is more than 120 years since the discovery of spiral galaxies, and naturally there has been much speculation on their origin. The vital clue is the composition of the arms, and it is now known that the arms are patterns of newly formed, and hence very luminous, stars. Thus the problem of spiral arms is only part of the broader problem of the origin of stellar systems in general. The various galactic forms of the Hubble morphological classification are differentiated by their different stellar systems, and so the problem of spiral arms is part of the basic problem of the origin of the Hubble types. For this reason the potential significance of any theory of spiral arms is vastly extended.
Relaxation Oscillations in Red-Giant Envelopes and the Symbiotic Stars
Authors: Wood P. R.
Published: July 2016

The spectrum of a symbiotic star consists of an M-type absorption spectrum, a B-type shell spectrum and nebula emission lines, the relative contributions of these three components varying with time. The light curves of the symbiotic stars vary with a semi-regular period typically 200-800 days while larger eruptions occur on a timescale of ~ 3.5 years. Some suggestions which have been advanced to explain the combination spectrum, variability and eruptive behaviour of the symbiotic stars are:

(a)

the symbiotic stars are binaries consisting of a hot and cool component.

(b)

the symbiotic stars consist of a single hot star surrounded by a large optically thick envelope giving the appearance of a hot continuum with the absorption spectrum of a cool star superimposed on it.

(c)

the symbiotic stars are single stars surrounded by a shock wave heated chromosphere.

Although some of the symbiotic stars are undoubtedly binaries (for example, T Coronae Borealis), observatienal evidence suggests that others may be explained by hypothesis (c) above. The calculations described below provide an explanation of the symbiotic stars in conjunction with hypothesis (c).
Microturbulent Velocities of Southern F-type Supergiants
Authors: Castley J. C.
Published: July 2016

Coudé spectra were obtained for a selection of giant and supergiant stars having spectral types in the range A9 to F2 to determine their atmospheric characteristics. The 12 members of Table 1 were compiled from The Catalogue of Bright Stars. This group of stars includes all known supergiants south of declination −15° and brighter than mv = 5.0 with spectral type between F5 and A5. Delta Canis Majoris (F81a) which has been the subject of many detailed investigations, was also observed to check for possible systematic errors in our equivalent widths. The spectra were obtained using the Coudé spectrograph of the 40 cm reflector at the University of Tasmania Observatory. Linear dispersions of 1.8Å mm−1 (0.12Å resolution) in the range 3600 to 4000Å and 2.4Åmm−1 (0.18Å resolution) in the range 4000 to 5000Å were used for stars brighter than third magnitude; 9Å mm−1 (0.4Å resolution) was used for stars fainter than third magnitude. The classification of 196 Car. was observed to be later (F8III) than the listed value and the spectrum of this star was not analysed further.
A Theory of Type I Solar Radio Bursts
Authors: Sy W. N. -C.
Published: July 2016

Type I radio bursts, as distinct from the continuum component frequently associated with them in a solar storm, are short-lived (0.1-2 s), narrow-band (2-10 MHz) bursts with frequency drift rates from 0 to 20 MHz s−1. They come from coronal regions close to the corresponding plasma levels, i.e. the frequency of radiation ω is close to the local plasma frequency ωp. They occur more frequently at frequencies above ~100 MHz but at times extend to frequencies as low as 20 MHz. Their observed equivalent brightness temperatures are usually about 109 K but they can reach 1011 K or higher. Except for an average decrease in polarization towards the limb and except for initial stages of a storm, type I bursts are strongly circularly polarized (approaching 100 per cent) in the sense of the O-mode.
Unusual Absorption of a Solar Type II Burst by ‘Shadow’ Type III Bursts
Authors: Kai K.
Published: July 2016

A Hα flare (12°N., 49°W.) on 1968 August 23d23h45m was followed by a short-lived type II burst whose dynamic spectrum, as recorded with the Culgoora radio-spectrograph, is shown in Figure 1. The type II burst had split-band structure; the upper band drifted from 130 MHz to 80 MHz, the lower band from 100 MHz to below 80 MHz (at the time the 25-74 MHz band of the spectrograph was less sensitive than the 74-220 MHz). Unusual spectral features can be seen in each split band. The most remarkable one is an absorption feature between 23h52m02s and 23h52m 10s – the depression in the bright type II emission along an ‘inverted U’ (between 120 and 85 MHz). Several other similar, though less marked, absorption features can be found between 23h51m45s and 23h52m30s.
On the Polarization Characteristics of Moving Type IV Solar Radio Bursts
Authors: Robinson R. D.
Published: July 2016

Any theory dealing with type IV solar radio bursts must explain the observed evolution of their brightness temperature and polarization. The behaviour of isolated, moving type IV sources is characterized by a long period of constant and low polarization during the major part of their lifetime, followed by a substantial increase in the degree of circular polarization during the declining phase. This behaviour puts severe constraints on and gives valuable clues as to the evolution of the physical conditions within the source.
The Temperature Structure of a Stellar Atmosphere Heated by Soft X-Rays
Authors: Wickramasinghe D. T.
Published: July 2016

In this paper we obtain an approximate expression for the temperature structure of a stellar atmosphere heated by an external flux of soft X-rays. Allowance is made for reradiation in both the soft X-ray and optical regions. As may be expected our results indicate that the temperature structure will be drastically changed from the grey T-T relation, particularly at low optical depths. The stronger lines should appear in emission with the possibility of a central absorption in certain circumstances. The present results are in general agreement with those of Strittmatter (1974).
Cosmic Ray Particle Diffusion and the Fokker-Planck Equation
Authors: Urch I. H.
Published: July 2016

The Fokker-Planck equation has been used by a number of authors (Jokipii 1966, 1971; Hall and Sturrock 1967; Hasselmann and Wibberentz 1968; Roelof 1968) to deduce the diffusion coefficients of cosmic-ray particles in the interplanetary magnetic field. However, these calculations suggest that the diffusion of particles perpendicular to the mean magnetic field is implausibly large; so large that the validity of a Fokker-Planck approach as applied to the interplanetary medium must be doubted.
Early-Type Emission Line Radio Stars
Authors: Wright A.E.
Published: July 2016

During the last few years, a new type of radio object has appeared in the literature: this is the Early Type Emission Line Star, or ETELS for short. These objects are possibly the most interesting radio object discovered since the pulsars. They are certainly more easily understood, since an explanation of their emission processes probably does not involve any ‘strange’ physics but only simple gas dynamics and thermal bremsstrahlung.
The Galactic Distribution and Kinematics of OH Stars (A Preliminary Discussion)
Authors: Bowers P.F.
Published: July 2016

The majority of OH/IR stars have been identified as M-type Mira variables, but there are a few cases where the stars have been identified as M supergiants or late-type semi-regular variables. A large number of OH sources have also been discovered with the 1612 MHz OH characteristics of OH/IR stars but no apparent optical or infrared counterparts. In several cases the velocities of these unidentified sources (OH stars) have been outside the velocity range of the neutral hydrogen distribution, suggesting that some of these sources may represent a population with a higher velocity dispersion than Population I objects (Kerr and Bowers 1974a, b). The lack of infrared and optical counterparts may indicate that the sources are quite distant, since identified OH/IR stars are often bright infrared objects. A large-scale 1612 MHz sky survey has therefore been initiated to study the galactic distribution and kinematics of the OH stars and to investigate the possibility that they may represent an older population of stars (Bowers et al. 1974).
Plans for the Australian Synthesis Telescope
Authors: Wellington K. J.
Published: July 2016

A major requirement of modern radio astronomy is the attainment of the highest possible angular resolution. This high angular resolution should be matched by a high sensitivity and by spectral and polarization capabilities. Study and experience have shown that no form of telescope is more effective in this respect than the aperture synthesis type. The past few years have seen a growing realization amongst astronomers, both here and overseas, of the need for a new synthesis telescope able to observe the full southern sky. This realization has been stimulated by several factors:
The Dynamics of the Magellanic Stream
Authors: Wright Alan E.
Published: July 2016

In this talk I shall describe briefly some of the theoretical ideas of the origin of the Magellanic Stream and then give a more personal view of the results of model fitting.

The Magellanic Stream definitely seems to be an extragalactic feature: the apparent connection of the Stream to the Magellanic Clouds and the continuity of the radial velocity profiles make it highly implausible that the Stream is a local foreground feature.
High Angular Resolution Stellar Interferometry
Authors: Davis John
Published: July 2016

The history and achievements of interferometric angular diameter measurements have been reviewed recently by Hanbury Brown (1974) and only a brief outline will be given here. As the title is intended to imply, the present discussion will be limited to interferometry involving baselines in excess of telescope aperture diameters.
A Synthesis Telescope at Molonglo
Authors: Mills B. Y. , Little A. G. , Joss G. H.
Published: July 2016

The major programs at the Molonglo Radio Observatory are nearing completion. Much can still be done using the existing 1 mile Cross-type radio-telescope (Mills et al. 1963) but, to tackle properly many of the current problems in radio astronomy, a fundamental change is required from a transit to a trackable radio-telescope, combined with an increase in the operating frequency and the resolution.
Cosmic Ray Induced Photomultiplier Noise
Authors: Gregory A. G. , Clay R. W.
Published: July 2016

Cosmic rays produce a component of photomultiplier noise which often dominates the high amplitude region of the noise pulse height spectrum and which is not reduced by cooling the tube. The source of the noise is Cerenkov radiation produced by individual high energy cosmic rays in their passage through the glass envelope of the tube, principally in the glass faceplate on which the photocathode is deposited.
Can Spontaneously Emitted Langmuir Waves Account for Type III Solar Radio Bursts?
Authors: Melrose D. B.
Published: July 2016

One of the major problems in the theory of type III solar radio bursts concerns the development of the two-stream instability. On the one hand, Sturrock (1964) argued that one expects the instability to develop rapidly, and if it does it should prevent the stream from propagating through the corona, contrary to observation. On the other hand, one appears to require that the instability develop partially, in the sense that there is some significant amplified emission of Langmuir waves, in order to account for the observed emission.
Period Changes of SV Centauri
Authors: Kvíz Z.
Published: July 2016

SV Cen is an eclipsing variable of the Beta Lyrae type and is especially known by its rapid changes of period. The system was studied photometrically and spectroscopically by Irwin and Landolt (1972). According to the previous study by O’Connell (1951) the system exhibits a 34-year periodicity.
Intensity of Low Frequency Recombination Lines
Authors: Batty M.J.
Published: July 2016

Owing to the comparative lack of radio recombination line observations of southern HII regions, it has not been so far possible to make an overall interpretation of the data for these sources. However, observations of the H90α and H252α transitions by McGee et al. (1975) and Batty (1974) respectively have usefully extended the frequency range of observations to cover ∼ 0.4 to 8.9 GHz for a few southern HII regions.
Airborne Infrared Astronomy
Authors: Thomas J. A.
Published: July 2016

Infrared astronomical observations using ground-based equipment are confined to the few ‘windows’ or observation ports allowed by our absorbing atmosphere, the chief absorbing molecules being water vapour and CO2. The majority of such observations have been made using broadband filters defining the photometric J, H, K, L, M, N and O bands. Some narrow band and spectral work (essentially all photometric) has also been carried out, particularly in the 8-14 micron window. From a very few high altitude, cold, dry sites (where the integrated water vapour content of the atmosphere above the site is consistently less than 1mm), it is possible to make observations at 35 and 345 microns. In Australia, the integrated water vapour content above us is typically 15 mm, only rarely dropping below 7 mm, so that long wavelength IR measurements simply cannot be made using ground-based instruments in Australia. Water vapour is fortunately not well mixed in our atmosphere and by raising our observational platform to a high enough altitude we can in fact achieve quite high transmission for all wavelengths from 10 microns to 1 mm, where we link up with microwave observations using essentially radio techniques.
Deuterium in the Galaxy
Authors: Brown R. D.
Published: July 2016

There have been a number of attempts made in the last decade or two to observe deuterium in parts of the universe other than here in Earth. It is of interest merely to detect deuterium elsewhere just as it is to detect the occurrence of any nuclide. However in the case of deuterium there is a special interest because in big-bang cosmologies the great majority of deuterium in the universe is considered to have been formed in the initial fireball (Wagoner, 1973). Any observation of the present abundance of deuterium thus might give information about the very early stages of the creation of the universe. Detailed studies of nucleosynthesis during the early expansion of hot big-bang universes have however indicated a particular feature of deuterium production. (Fig. 1) The mass fraction produced X(D) is a very sensitive function of the size of the universe, as measured say by the present baryon density ϱb. Other nuclides that are mainly produced in the early expansion, such as 4He, have mass fractions less dependent on ϱb. Thus if we adopt the big-bang model for our universe we can determine ϱb from observations of X(D). Apart from any intrinsic interest in the present density of the’universe, there is considerable interest in whether the value is great enough for the present expansion to halt and go over to a collapse — or so small that the expansion of the universe will go on forever.
The Cassegrain Echelle Spectrograph at Mt John Observatory
Authors: Heamshaw J. B.
Published: July 2016

The standard formula for the resolving power R(= λ/Δλ) of an astronomical grating spectrograph is

Here L is the linear size of the grating, perpendicular to the direction of the grooves, θB is the blaze angle of the grating, θS is the angular size of the slit, projected back on to the sky, and D is the diameter of the telescope objective. The formula is valid for gratings used in the Littrow condition, when the angle of incidence α, and the angle of diffraction β, are both close to θB.
Balloon Observations of the X-ray Pulsar Vela XR-1
Authors: Duldig M. L. , Emery M. W. , Fenton A. G. , Fenton K. B. , Greenhill J. G. , Thomas R. M.
Published: July 2016

The initial flight of the University of Tasmania balloon-borne X-ray telescope was made from Parkes on Dec. 2, 1976. During the flight, enhanced X-ray emission was observed from the directions of 3U0900-40 (Vela XR-1), GX301-2 and the Galactic Centre. In this paper we report on the performance of the payload during the 11 hour flight and describe the preliminary results thus far obtained.
A new Pulsar Survey
Authors: Lyne A. G.
Published: July 2016

A new survey of the southern sky for pulsars is being carried out jointly by the University of Sydney and the CSIRO Division of Radiophysics. J. M. Durdin, M. I. Large and A. G. Little from Sydney University have been working with R. N. Manchester, J. H. Taylor and myself from Radiophysics. This paper provides a brief description of the experiment and an account of progress to date.
The Limiting Magnitude of the ESO-B and SRC-J Sky Survey
Authors: White G. L.
Published: July 2016

As part of an identification programme undertaken on the southern section of the Molonglo Deep Sky Survey of Radio Sources, the limiting magnitudes of some of the available ESO-B films and SRC-J films and plates in this area have been determined. The Molonglo Deep Sky Survey has been described by Robertson (1977). The southern section comprises a 45’ wide strip centred about declination -62° and stretching in an irregular fashion from 18h 25m to 00h 16m.
The 20keV Break in the Diffuse X-ray Background Spectrum
Authors: Hudson R. M. , Thomas R. M. , Duldig M. L.
Published: July 2016

In this paper we report an independent determination of the Location of the break (change in spectral index) in the spectrum of the diffuse X-ray background by applying a simple analysis technique to data already in the literature.
Coronal Magnetic Structure near the Source Region of a Type II Radio Burst
Authors: Stewart R. T.
Published: July 2016

The magnetic structure in the source region of a type II burst and along the path of the type II disturbance has remained an enigma despite over 20 years of radio observations of the Sun (see e.g. reviews by Wild and Smerd (1972) and McLean (1974)). This paper describes the first radioheliograph observations of a type II burst near coronal magnetic structures depicted by soft X-ray pictures. It will be shown that three separate lanes in a type II burst are associated with three separate source regions each located almost radially above a soft X-ray loop. To explain these observations a model is derived in which a wide-fronted m.h.d. disturbance travels from the flare explosion along magnetic field lines and then intersects successively with three coronal streamer structures each located above a soft X-ray loop. An estimate of the magnetic flux density along the soft X-ray loops is obtained from the velocity of the m.h.d. disturbance.
On the Feasibility of a Southern Cooperation
Authors: Kvíz Z.
Published: July 2016

Although the gap between the observational data from northern and southern hemisphere started recently to narrow, the long neglected southern hemisphere is still far behind the northern. I have especially in mind binary and variable stars. The systematic research in this field in the south is not satisfactory and many interesting objects still await to be properly observed and many to be discovered. We are now grateful to our predecessors who 70 years ago started the photographic patorl of northern sky so that we are now able to trace back the behaviour of many interesting objects such as X-ray sources; we may follow back the changes of light curves and derive important conclusions from the changes of periods.
Heliograph Observations of both Fast Drift (Type III) and Continuum (Type IV) Solar Emission from the one Source high above the Solar Limb
Authors: Duncan R. A.
Published: July 2016

Many authors (e.g. Magun et al. 1975) have debated the question ‘does solar type IV continuum emission arise through Langmuir wave conversion or through gyro-synchrotron emission?’ Culgoora radio spectrograph and heliograph observations of the late stages of a recent (7 September 1977) type II, IV event showed both type IV* (continuum) and transient type III (electron-beam) emission coming from the same source, high above the solar limb. These observations suggest that this particular type IV continuum arose through a mechanism similar to that of the type III, probably fundamental Langmuir-wave emission, in a corona with a tenfold enhancement of plasma density.
Circinus X-1 at 408 MHz
Authors: Little A. G.
Published: July 2016

The radio source associated with Circinus X-1 has been observed several times at Molonglo since 1970 and some of these observations have already been reported (Whelan et al. 1977). In 1977 the source was again observed, this time for 17 consecutive days and during these observations the position and flux of the reference source 1505-56.9 were more precisely determined. A few sporadic observations have also been made in 1978. This note brings together the new observations and all the old measurements which have been corrected on the basis of the new data for 1505-56.9 Other observations have been made which were not calibrated against this source but these have not been included in this note since they are less well calibrated.
The Time Scale of Decimetre Flux Density Variations
Authors: McAdam W. B.
Published: July 2016

One of the critical parameters for a theory of emission from QSOs is the time scale of the variations in this emission. For many sources, changes occur faster than the light travel time across the source disk size as determined by VLBI observations. If the decimetre flux density is assumed to come from a small core, appropriate to the time scale of its variations then the brightness temperature must be far greater than ~ 1012 K allowed by the incoherent synchrotron process. These difficulties have been examined (Jones and Burbidge 1973; Burbidge and Stein 1975) using the QSO 2251 + 158 (3C454.3) as an example against which to test the theory. In this paper, I examine the time scale of the variations in 46 sources and show that most of these vary significantly within 2 years. The most rapid changes are in the QSOs 0736 + 017 and 1504–166 which have changed 40% within a few months — an order of magnitude faster than 2251 + 158.
The Masses and Origin of Carbon Stars
Authors: Bessell M. S. , Wood P. R. , Evans T. Lloyd
Published: July 2016

Carbon stars have always been amongst the most intriguing of stars which show grossly non-solar abundances. All such stars raise the questions:

(a) at what stage of stellar evolution does this peculiar abundance phase occur?

(b) do all stars pass through this stage?

(c) is the phase significant in the overall picture of galactic nucleosynthesis?
Photometry and Spectroscopy of Long Period Variables in the Magellanic Clouds
Authors: Wood P. R. , Bessell M. S. , Fox M. W.
Published: July 2016

Many of the important events in the life of a star occur, or are thought to occur, during the red giant or supergiant phase of evolution. For example, in heavy and intermediate mass stars supernova explosions terminate normal evolutionary processes while in lower mass stars the stellar envelope is entirely removed giving rise to planetary nebulae and, subsequently, white dwarfs. Theoretical calculations suggest that before the onset of these rather drastic events, a significant amount of nucleosynthesis occurs, giving rise to enhanced surface abundances of He, C, N and s-process elements (e.g., Iben and Truran 1978; Renzini and Voli 1981); loss of the envelope material by stellar winds, planetary nebula ejection and supernova explosions produce overall galactic enrichment in these elements.
Physical Characteristics of a Polytrope Index 5 with Finite Radius
Authors: Murphy J. O.
Published: July 2016

In astrophysics the polytropic law with index n is commonly used as a means of imposing a simple and ordered physical structure on a gaseous (or smoothed discrete) system. In many instances it would be preferable to be able to introduce a polytropic density variation analytically into the basic theory rather than numerically at the computational phase. It is perhaps unfortunate that the three well known classical analytical E type solutions of the Lane-Emden equation for n = 0, 1 and 5 all have some constraining physical features; specifically, the polytrope n = 0 has uniform density and hence arbitrary radius, when n = 1 the mass and radius are independent of each other and the solution cannot be transformed homologically, and because the first zero ξ1 = ∞ for n = 5 the corresponding polytropic model has infinite extent and central condensation. In contrast, and unlike most stars, the two finite radius models have central condensations which ~ 1.
Magnetic Prandtl Number and Astrophysical Convection
Authors: Murphy J. O. , Lopez J. M.
Published: July 2016

In the astrophysical context, where the effects of a magnetic field on stellar convective processes have to be taken into account, we have ϰ > > η > > ν (Weiss 1977) where ϰ, η and ν are respectively the thermal, magnetic and viscous diffusivities.
Alpha Centauri
Authors: Bessell M. S.
Published: July 2016

The nearest star α Centauri is a triple system. The star α Cen, one of the pointers to the Southern Cross, is itself a −0.3 mag visual binary consisting of a α Cen A, a G2V star popularly considered to resemble the Sun, and α Cen B, a KOV star. The orbital period is 80.089 years, the semimajor axis is 23.5 AU, the distance 1.34 pc, the masses are 1.11 and 0.92 (±0.03) M⊙ (Kamper & Wesselink 1977). The third star, Proxima Cen (V645 Cen) is a faint common proper-motion companion separated from α Cen AB by about 2°. It is known to most people only by virtue of being slightly closer to the Sun than is α Cen A, and therefore actually the closest star.. This 11th mag flare star is undoubtedly coeval with a α Cen AB, but being the least massive by a considerable margin, may have been ejected from the system shortly after formation.
Two-Photon Absorption and the Cyclotron Line in Her X-1
Authors: Melrose D. B. , Parle A. J.
Published: July 2016

The cyclotron line in Her X-1 is a hard X-ray feature at ≈ 58 keV discovered by Trümper et al. (1977). A cyclotron emission line at about this energy had been predicted by Gnedin and Sunyaev (1974) and Basko and Sunyaev (1975). They developed a model for the infall of accreted matter onto a magnetized neutron star’s surface, and concluded that hot spots would form at the polar caps and radiate X-rays. They predicted that the optional depth for bremsstrahlung would be less than unity, that for Compton scattering greater than unity and that for cyclotron absorption much greater than unity. A cyclotron line is then implied due to the emission spectrum lying below the black-body spectrum except near the cyclotron energy where it rises up to the black-body limit. More recent developments of these background ideas have been reviewed by Börner (1980).