bluuebunny/crossref_metadata_2025 huggingface dataset:
Qantization Errors in the Digital Implementation of “CLEAN”
Authors: Chen C. F.
Published: July 2016

Since its introduction by Högbom (1974), ‘clean’ has been widely used to restore images from the aperture synthesis techniques of radio astronomy. The method iteratively subtracts from the maximum deflection of the image the point source response and so deconvolves it with some loop gain;

where yn = residue image.

xn = deconvolving beam derived by matching the peak of the beam to where yn has the maximum deflection and band-limiting the size of beam within the image,

An = a scalar in accordance with the loop gain applied to the residue image, and

n = iteration.

Ideally, the residue image converges to noise level. In digital processing, the method is implemented with special purpose hardware, general purpose computer, or array processor. In all cases the image to be restored (the ‘dirty’ map), the space-invariant beam used to deconvolve the image (the ‘dirty’ antenna pattern) and the loop gain are stored in binary format in memories and registers with finite wordlength. (Wordlength is an economic factor both in hardware and software implementations).
18-25 GHz low-noise Line Receiver for the Tidbinbilla 64-m Antenna
Authors: Jauncey D. L. , Batty M. J. , Gay G. J. , Moore C. R. , Batelaan P. J. , Clauss R. , Dickinson D. , Gulkis S. , Klein M. , Kuiper T. , Morris G. , Neff D. , Ricketts W. B. , Swanson P.
Published: July 2016

A K-band (18-25 GHz) reflected-wave ruby maser (Moore and Clauss 1979) has been borrowed from the National Radio Astronomy Observatory for radio astronomy use on the NASA 64-m antenna of the Deep Space Network at the Tidbinbilla Tracking Station, near Canberra. The purpose of the installation is to provide additional sensitive spectral line, continuum, and VLBI capabilities in the southern hemisphere. Previous measurements at 22.3 GHz (λ = 13.5 mm) determined that the Tidbinbilla 64-m antenna has a peak aperture efficiency of ˜22%, a well-behaved beam shape and consistent pointing (Fourikis and Jauncey 1979). Before installing the maser on the antenna a cooled (circulator) switch was added to provide a beam-switching capability, and a spectral line receiver following the maser was incorporated. The system was assembled and tested at JPL in late 1980 and installed at Tidbinbilla early in 1981. We give here a brief description and present some of the first line observations made in February and March 1981. Extensive line and continuum observations are planned with the present system and a program is under way to determine the telescope pointing characteristics.
Time-Dependent Thermal Convection
Authors: Lopez J. M. , Murphy J. O.
Published: July 2016

The temporal behaviour of Rayleigh-Benard convection has attracted considerable attention in recent years, both from an experimental and theoretical point of view. Experiments (eg. Gollub and Benson 1980) have demonstrated a complicated array of non-linear behaviour, as well as the need for a model which will at least qualitatively describe what is observed.
Eruptive Prominences and Long-Delay Geomagnetic Storms
Authors: Wright C. S.
Published: July 2016

During recent years a firm relationship has been established between disappearing solar fragments and geomagnetic disturbances (Joselyn and McIntosh 1981; McNamara and Wright 1982; Wright and McNamara 1983). Wright and McNamara (1983) showed that the average magnitude and delay of the geomagnetic disturbance depended upon the size of the filament.
Disappearing Solar Filaments and Interplanetary Shock Waves
Authors: Wright C. S.
Published: July 2016

The close association between flare events having metric radio type II and type IV bursts and the subsequent occurrence of sudden commencement geomagnetic storms is well known. In such cases it has been amply demonstrated (e.g. Malitson et al. 1973; Cane et al. 1982) that the sudden commencement (SC) is caused by the same magnetohydrodynamic shock which originates near the Sun and which produces the type II burst. Recently, a study of geomagnetic storms thought to be associated with the disappearance of filaments from quiet regions of the Sun (Joselyn and McIntosh 1981) showed that several of these storms began with marked sudden commencements.
A Radio Polarimeter-Spectrometer
Authors: Hall P.J. , Hamilton P.A. , McCulloch P.M.
Published: July 2016

The polarization characteristics of celestial radio signals are a major part of the observable nature of the radiation. Stokes polarimeters, instruments for measuring the complete polarization properties of radiation, are usually narrowband devices in order to minimise depolarization effects originating in the source or in the medium through which the radiation propagates. To measure the broadband polarization behaviour of a source, a Stokes polarimeter-spectrometer is required. Such an instrument allows the frequency dependence of each Stokes parameter to be deduced, making it possible to apply corrections to each parameter to account for known forms of polarization distortion (e.g. Faraday rotation). It is also possible to remove delay distortion from impulsive sources such as pulsars by processing the spectrometer data according to the usual de-dispersion algorithms. In some studies observation of distortion phenomena may be the major aim and a polarimeter spectrometer greatly facilitates measurements of these effects.
HYDRA — The New Observing Environment at the Parkes Radio Telescope
Authors: Argyros J.D. , Brown D. , Deane J.F. , Firth M. , Haynes R.F. , Henderson A. , Hunt A.J. , Lee P.Y. , May H. , Mulhall P.S. , Rayner P.T. , Willing M.
Published: July 2016

After 21 years the Parkes radio telescope has undergone a major refit. A new VAX-11/750 running VMS has replaced the aged Digital Equipment Corporation PDP-9 computer. Other new equipment includes two systems not previously available — the Mk II RING communication system (Willing and Abies 1983) and the ‘observer workstations’.
Multi-Mode Study of Time-Dependent Thermal Convection With Hexagonal Planforms
Authors: Lopez J. M. , Murphy J. O.
Published: July 2016

Truncated modal expansions have provided a powerful, reasonably accurate and flexible approach to the problem of non-linear thermal convection. They permit tractable numerical solutions of three-dimensional cellular motions, as well as readily accommodating large density variations, time dependence, rotation and magnetic fields.
Evolutionary Calculations for Planetary Nebula Nuclei with Continuing Mass Loss and Realistic Starting Conditions
Authors: Faulkner D. J. , Wood P. R.
Published: July 2016

The mechanism by which planetary nebula (PN) shells are ejected is still subject to considerable uncertainty. It is generally assumed that the precursors of these objects are low mass (M< 5 M⊙) asymptotic giant branch (AGB) stars, and that the nucleus of a planetary nebula (NPN) is undergoing a final gravitational contraction to the white dwarf state. The shell consists of some or all of the remaining unburnt (though not necessarily uncontaminated), hydrogen-rich material out of which the star was originally formed.
Ultra-High Energy γ-Ray Astronomy using an EAS Array: Search for Emission From 100 MeV Sources
Authors: Protheroe R. J. , Clay R. W.
Published: July 2016

Recently, a new branch of astronomy has emerged following the detection of ultra-high energy (UHE) γ-ray emission from Cygnus X-3 by Samorski and Stamm (1983). This discovery was made using the extensive air shower (EAS) array of the University of Kiel, Germany. Such arrays are designed to detect EAS, the cascades of secondary particles (mainly electrons and protons), which are generated in the atmosphere by the interaction of cosmic ray nuclei of energy greater than ˜ 1015 eV. These arrays are also sensitive to EAS initiated by primary γ-rays and, depending on their design, have angular resolutions as good as the SAS-II and COS-B γ-ray telescopes which operated at ˜ 100 MeV energies. At present, there is no effective way to veto proton or nucleus-initiated EAS and so one must look for a significant excess of EAS from within a cone of resolution centred on a suspected source direction.
The Parkes-Tidbinbilla Interferometer
Authors: Norris R. P. , Batty Michael J. , Kesteven M. J. , Wellington K. J.
Published: July 2016

We report the development of a radio-linked interferometer which uses the 64-m telescope at Parkes, NSW, and one of the NASA antennas (64-m or 34-m) at Tidbinbilla, ACT. With a baseline of approximately 275 km, this is the world’s longest real-time interferometer; it will be usable at frequencies of 1.6, 2.3, 8.4, and 22 GHz to give angular resolutions of 0.13, 0.09, 0.03, and 0.01 arcsec respectively. The interferometer has already operated successfully in a limited mode and is expected to become fully operational in its initial configuration by September 1985. Operation at a range of frequencies and with progressive enhancements is planned up to the commissioning of the Australia Telescope in 1988.
An Optical and X-ray study of the Radio Source 3C75
Authors: Caganoff S. , Bicknel G. V. , Carter D.
Published: July 2016

3C75 consists of a pair of twin-jetted radio galaxies near the centre of the cluster Abell 400 which is a strong extended X-ray source. Fibre spectroscopy from the AAT, combined with number counts of the galaxies in Abell 400 give the gravitational potential of the cluster which is used to model the X-ray source. The inferred pressure of the X-ray gas suggests that the lobes of the radio source are probably confined. Evidence of excess X-ray emission near the centre of the cluster is also found.
Modelling Clusters of Galaxies
Authors: Teague P. F. , Carter D.
Published: July 2016

Thorough investigation of clusters of galaxies involves the complete modelling of their dynamics and structure. Presented here is a description of such a substantial project utilizing a sample of several rich southern clusters of galaxies. Incorporating results from radial velocity analyses of cluster galaxies and X-ray images of the clusters into rigorously constructed models of the cluster potential well and atmosphere will enable the dynamics, structure and evolution of clusters to be tied down.
Physical Structure of a Sequence of Two Zone Polytropic Stellar Models
Authors: Murphy J. O. , Fiedler R.
Published: July 2016

Expressions for the physical structure of a sequence of two zone polytropic stellar models, based on composite analytical solutions of the Lane-Emden equation with indices n = 1 and n = 5, hâve been determined. The coefficients of vibrational stability for radial oscillations of this sequence of models have also been calculated and it is found that increasing the extent of the n = 5 outer zone has a stabilizing effect.
Time Dependent Multimode Hexagonal Magnetoconvection
Authors: Lopez J. M. , Murphy J. O.
Published: July 2016

The time dependent multimode equations for magnetoconvection have been solved numerically for a range of parameter values and cell sizes. The solutions demonstrate the nonlinear interactions between the different scales of motion and how the induced magnetic field is concentrated into the smaller length scale. The generation of mean kinetic and magnetic helicity occurs at low Prandtl number which has significant physical interpretations in the solar situation.
Culgoora Catalogue of Solar Radio Noise Storms, 1973 to 1984
Authors: Stewart R. T. , Eason Helen M. C. , Heisler L. H.
Published: July 2016

A unique data set of 160 MHz solar noise storm positions and polarizations covering a complete sunspot cycle interval from the Skylab period of 1973 through the Solar Maximum intervals of 1980 and 1984 is presented in the form of 27.28-day synoptic plots.
Uranus after Voyager 2 and the Origin of the Solar System
Authors: Prentice A. J. R.
Published: July 2016

The discoveries made by the Voyager 2 spacecraft at Uranus in January 1986 are discussed in the light of the modern Laplacian theory for the formation of the solar system. Various accounts of this theory, which has as its basis the concept of supersonic convective turbulence, have been presented at previous meetings of the ASA (Prentice 1977, 1979, 1981a). The most important confirmation by Voyager was the discovery of 2 new satellite groups near orbital radii 2½ RUand 3½ RU(RU= Uranus’ equatorial radius = 26, 200 km), as first predicted in 1977. The discovery that the densities of the Uranian satellites are consistent with these bodies having condensed in a single compositional class, consisting of anhydrous rock, NH3ice and CH4.6H2O clathrate hydrate in normal solar proportions, confirms the hypothesis that the chemistry of all planetary/regular satellite systems are accounted for by a single choice of the turbulence parameter, namely β = 0.107 ±0.001. The implication of the Voyager data for the origin of comets is also discussed.
A Southern Hemisphere Ammonia Survey
Authors: Peters W. L. , Forster J. R. , Gardner F. F. , Whiteoak J. B. , Kuiper T. B. H.
Published: July 2016

A spectral line survey for interstellar NH3 is being carried out using the 64-m telescopes at Parkes and Tidbinbilla. Both telescopes are equipped with K-band maser receivers yielding system temperatures below 100 K. The preliminary survey is being made with the Parkes antenna (beam = 1.35 arcmin), with follow-up mapping of the more interesting sources at Tidbinbilla (beam = 0.9 arcmin). The selected sources have in general been HII regions from the H2CO surveys made at Parkes. Statistical results from initial observations of the (1, 1), (2, 2), and (3, 3) lines in the preliminary survey are presented.
Adult Classes in Astronomy at Sydney University (1976-1986)
Authors: O’Byrne J. W. , White Graeme L. , Harnett J. I. , Biggs J. D.
Published: July 2016

Adult education classes in astronomy have been conducted in Sydney for many years. The University of Sydney has been especially prominent in this field, holding classes in conjunction with the Sydney WEA prior to 1983, and independently since then. In the last 11 years, most of these courses have been conducted by postgraduate students from the Astrophysics and Astronomy departments in the University’s School of Physics. This paper describes these courses and points out some future possibilities in the teaching of astronomy to adult classes.
International Ultraviolet Explorer and The Interstellar Medium
Authors: Dopita M. A.
Published: July 2016

J. Rahe of Bamberg reported on IUE observations of comets Sargent (1978) and Bradfield (1980).
The University of Tasmania 1.04 M Telescope
Authors: Waterworth M. D.
Published: July 2016

The 1.04 m telescope and auxiliary instrumentation conceived some ten years ago, are now operational and starting to produce results. Whilst the original purpose of the telescope was high dispersion spectroscopy alone at Coudé focus, access to a folded Cassegrain focus has been added to enable photometric observations to be made.
A Fast, Real-Time Processor for Speckle Interferometry
Authors: Cole T. W.
Published: July 2016

Speckle interferometry (Labeyrie 1970, 1976) is one way of overcoming the blurring effect of the atmosphere in optical astronomy. When a short exposure is taken of an image, the seeing disc (typically several seconds of arc across) is seen to contain structure (speckles) down to the resolution limit of the telescope (0″.03 arc for the Anglo-Australian telescope). A second exposure 10 or so milliseconds later will show a different pattern of structure because the atmospheric irregularities will have changed. Multiple stars or source components within the same angular range of atmospheric irregularity (i.e. isoplanatic patch several seconds of arc across) will produce similar but displaced speckle patterns, and geometrical details of the components can be obtained from an autocorrelation analysis of the speckle pattern (Dainty 1975).
A New Type of One-Bit Digital Correlator
Authors: Cole T. W.
Published: July 2016

Given an ordered set of samples {ai} of some function, then the autocorrelation of that function is the mean lagged product of these samples.
The Influence of the Rayleigh and Prandtl Numbers on Convective Heat Transport in Stars
Authors: Murphy J. O.
Published: July 2016

The two important parameters which essentially determine the nature of the convective regime, and consequently the total heat transported by convective processes, across an unstable layer in a star are the Rayleigh and Prandtl numbers defined by (Chandrasekhar 1961)

where ν is the coefficient of kinematic viscosity, x is the coefficient of thermal diffusivity and α, g, d, ΔT are respectively the coefficient of thermal expansion, acceleration due to gravity, depth of the fluid layer and temperature difference across the layer. In addition, the horizontal scale of the convection cell is determined by the horizontal wave number a and for convection to be established R must be greater than the critical value at marginal stability, Rc, which is a function of a, given by

when the free boundary conditions apply.
A Numerical Investigation of Rotational Instabilities in Differentially Rotating Polytropes
Authors: Lorimer G. S. , Monaghan J. J.
Published: July 2016

All studies of circulation in stars have been based on a linear perturbation analysis (e.g. Sung 1975). This analysis establishes criteria for the onset of circulation and, if the perturbations remain weak, allows the circulation pattern to be determined. (For a survey see Tassoul 1978).
A Canonical Ensemble Description of Three-body Disruption
Authors: Monaghan J. J.
Published: July 2016

The statistical theory of strong three-body interactions (Monaghan 1976a, b, Nash and Monaghan 1978) is based on the assumption that the motion of the system in phase space is ergodic, and that the energy and angular momentum are the only isolating integrals. The a priori phase space is infinite because the system is not confined by walls, but this is only a formal difficulty since the numerical calculations show that the motion takes place in a finite region of ordinary space and this fact can be incorporated in the statistical description. The probability density of the system in phase space is essentially Gibb’s Micro-Canonical ensemble.
Radio Evidence for Electron Acceleration by Transverse Shock Waves in Herringbone Type II Solar Bursts
Authors: Stewart R. T. , Magun A.
Published: July 2016

Perhaps the most direct evidence to date for shock wave acceleration of electrons in the solar corona is provided by radio observations of Type II bursts containing herringbone structure (Roberts 1959). On spectral records the herringbones appear to resemble miniature forward and reverse drift Type III bursts extending above and below the Type II backbone.
Pulsar Observations with Microsecond Resolution
Authors: Allen R. K.
Published: July 2016

Observations of pulsar radio-emission at high time resolutions are severely constrained by interstellar dispersion.
Spot Modelling of AB Dor, 1980-1991
Authors: Anders G.J. , Coates D.W. , Thompson K.
Published: July 2016

Some results of spot modelling for 18 light curves of AB Dor are presented, covering the period 1980-1992. Using the technique of Budding and Zeilik (1987) to determine spot parameters, it is shown that photospheric spots on this star tend to form in one of two longitude belts separated by approximately 180 degrees. This can be compared to the similar active longitudes proposed by Zeilik et al.(1988, 1989) for the RS CVn stars SV Cam and RT And. The change in overall light level of AB Dor over the past 12 years indicates the possibility of a solar-type spot cycle although more photometric observations will be needed to confirm this.
Curvature Emission and Absorption: Single Particle Treatment
Authors: Luo Q. , Melrose D. B.
Published: July 2016

The absorption counterpart of curvature emission is reexamined based on the Landau-Lifshitz approach. Early derivations led to the conclusion that maser emission is not possible, but these early derivations neglected a drift effect which was first discussed by Zheleznyakov and Shaposhnikov. When the drift effect is included, the derivation implies that curvature maser emission is possible. It is shown that for maser emission to be possible, the Lorentz factor needs to satisfy γ ≳ 103 for radius of curvature of the magnetic field lines RB ≈ 106 to 109cm and frequency ω ≈ 107 to 1011 s−1. Possible application to pulsars is discussed.
IRIS: What can it do tor you?
Authors: Allen David
Published: July 2016

Described here is the new infrared camera/spectrograph, IRIS, that was brought into operation at the Anglo-Australian Telescope early in 1991. A number of scientific discoveries are used to demonstrate the capabilities of the instrument.
The Magnetic Fields of Pulsars, Electrons and the Sun
Authors: Cole K. D.
Published: July 2016

An apparent connection is reported between the magnetic field strengths inside an electron, in newly born pulsars, and the sun. It is argued that the upper limit to the strength of magnetic field which seems to exist is that which would permit emission of a photon at the non-relativistic electron gyrofrequency, with energy of the order of the electron rest mass. The strongest magnetic fields at the surface of polar regions of pulsars conform to this. By equating approximately the rest mass of an electron to its magnetic energy, the same magnetic field is found inside the electron. It is proposed that magnetic field building ‘blocks’ called M-particles are formed by a variant of the electron-positron spin-zero annihilation. The particles become as tightly stacked as possible to form the macroscopic magnetic field of the newly born pulsar. The sun’s present magnetic moment is described by a pulsar-sized object at its centre, with the maximum packing of M-particles. The hypothesis may have a bearing on the formation of magnetic fields in celestial bodies, and on the secular variation of the magnetic fields of the sun and the Earth.
Numerical Modelling of Star Formation in GMCs
Authors: Lattanzio John C. , Monaghan J.J.
Published: July 2016

Although stars can be approximated very satisfactorily by spherical models, it is clear from observations of star forming regions that the break-up of molecular gas to form proto-stars is a highly complex process that cannot be approximated simply. As a consequence, the theoretical picture of fragmentation, which is based on assuming that fragmentation occurs in uniform, static, isothermal clouds, is too crude to provide a guide to the star formation process. The alternative is to simulate the fragmentation process numerically with the ultimate aim of evolving the gas to proto-stars. The difficulties involved with this procedure are discussed in this paper. We also discuss our proposed solution to this problem, together with a very preliminary calculation.
A Catalogue of ‘Southern’ Radio Sources with Accurate Positions
Authors: White Graeme L.
Published: July 2016

A list of 901 radio sources with positional accuracies better than 0.5 arcseconds has been prepared from seventeen lists of radio source positions found in the literature. This compilation includes all such sources south of declination + 48° (the northern declination limit of the Compact Array of the Australia Telescope National Facility). Where available, optical identifications, optical magnitudes and redshifts are given as well as total-power flux densities.
Radar Studies of the Orbits of Small Meteoroids
Authors: Baggaley W. J. , Bennett R. G. T. , Steel D. I. , Taylor A. D.
Published: July 2016

A description is given of a radar facility operating in New Zealand which measures the atmospheric trajectories and hence heliocentric orbits of earth-impacting meteoroids having radiants with declinations +5° < δ < −30° down to a limiting radar meteor magnitude of +13 (corresponding to particle sizes of ~100 μm, masses ~10−6 g). The data handling capacity of the facility permits recording, orbit reduction and efficient presentation of orbital data using graphical packages to be carried out on a routine basis. The daily yield is ~1500 individual orbits with >3×105 secured to date; this is greater than the number determined in all previous meteoroid orbit surveys combined and forms a major southern hemisphere database for dynamical studies of the solar system meteoroid population.
Regression Model for the 22-year Hale Solar Cycle Derived from High Altitude Tree-ring Data
Authors: Murphy J. O. , Sampson H. , Veblen T. T. , Villalba R.
Published: July 2016

Initially some simple analytical properties based on the annual Zürich relative sunspot number are established for the 22-year Hale solar magnetic cycle. Since about AD1850, successive maximum sunspot numbers in a Hale cycle are highly correlated. Also, a regression model for the reconstruction of the 22-year Hale cycle has been formulated from proxy tree-ring data, obtained from spruce trees growing at a high altitude site in White River National Forest in Colorado. Over a considerable fraction of the past 300 years to AD1986, the ring-index time series power spectrum exhibits a strong 22-year periodicity, and more recently a significant spectral peak (at the 95% confidence level) at approximately 11 years. The model shows that the greatest variation in ‘amplitude’ in the magnetic cycle occurs over the early decades of the eighteenth century, when the sample size is small. Thereafter, a nearly constant amplitude is maintained until about AD1880 when a break occurs in both phase correspondence and amplitude, extending over the next three cycles. From AD1950 the signal recovers phase with the solar cycle, with reduced but increasing amplitude.
Magnetic Braking in Single and Binary Stars
Authors: Li Jianke
Published: July 2016

We discuss the basic concept and the problems of magnetic braking via magnetically controlled hot plasmas in late-type stars. We investigate the magnetic braking process in special magnetic field structures in both single stars and binaries. We find that in single solar-type stars, the high-order component of the observed complicated fields can account for the braking rate of the present Sun. However, this component cannot account for the braking rate of young solar-type stars, even though this field is much stronger than the simple (monopolar or dipolar) field usually adopted in braking models. For magnetically interacting cataclysmic binaries, the magnetic fields of the white dwarf greatly change the magnetic fields on the main-sequence secondaries. In particular, in synchronously rotating magnetic CVs (AM Herculis systems) magnetic braking may even turn off if the white dwarf magnetic field is sufficiently strong. These results suggest that the magnetic field structure has a crucial effect on magnetic braking.
Is SN 1987A Entering a New Phase of Evolution?
Authors: Stathakis R. A. , Cannon R. D. , Spyromilio J.
Published: July 2016

Optical spectra of the ejecta of SN 1987A taken at the AAT now cover seven years of evolution. In recent years, SN 1987A has been in a phase known as freeze-out. The timescales for recombination have exceeded those of energy deposition, and the ionisation structure has become fixed. During this phase, cooling is slow and the optical spectrum has been extremely stable. Our latest spectrum, however, shows significant change. [FeI] and [FeII] emission from iron-rich clumps has dominated the optical emission from the supernova over the last four years. All the [FeII] features have disappeared in our latest spectrum from December 1993 and model fits of [FeI] features indicate that these clumps have cooled to the critical temperature of 1000 K. They may be entering a phase of rapid cooling known as the infrared catastrophe. In addition, emission at high velocities has strengthened, in line with the predictions of freeze-out. SN 1987A may be entering a new, and previously unobserved, phase in supernova evolution.
The Classification of M 1-78
Authors: Gussie G. T.
Published: July 2016

The published properties of M1-78 are discussed with the purpose of resolving the object’s classification as either a planetary nebula or an ultracompact HII region. A classification as a planetary nebula is rejected primarily because of the high luminosity of the object, but because of the chemical composition and expansion velocity of the nebula, a novel classification is proposed instead: that of an ultracompact HII region with a post-main sequence central star (possibly a WN star). It must therefore follow that observable ultracompact HII regions persist beyond the main sequence lifetimes of at least some massive stars, and so cannot be transient phenomena that are seen only during pre-main sequence or early main sequence evolution.
Deep Survey of the Radio Continuum Emission along the Southern Galactic Plane at 2·4 GHz
Authors: Duncan A. R. , Stewart R. T. , Haynes R. F. , Jones K. L.
Published: July 2016

We have just completed the observational stage of a 2·4 GHz survey of the Southern Galactic Plane, using the Parkes radiotelescope, between 238° ≤ l ≤ 365° and with a latitude range of at least |b| ≤ 5° (beamwidth ~9 arcmin). The survey details both continuum emission and linear polarisation down to rms noises of approximately 12 and 4 mJy/beam respectively. It is the most sensitive survey to date of the southern plane at this frequency and should nicely complement the Effelsberg northern plane surveys in addition to the recent southern surveys such as the 843 MHz MOST survey and the 5 GHz PMN survey. The total-power maps are now completed, and reduction of the polarisation data is still in progress. In addition to compact HII regions and extragalactic sources, we are detecting on our total-power images a considerable amount of large-scale structure, and a significant number of new SNR candidates and spur-like features.
Induced Three-wave Interactions in Eclipsing Pulsars
Authors: Luo Qinghuan , Melrose D. B.
Published: July 2016

Three-wave interactions involving two high-frequency waves (in the same mode) and a low-frequency wave are discussed and applied to pulsar eclipses. When the magnetic field is taken into account, the low-frequency waves can be the ω-mode (the low-frequency branch of the ordinary mode) or the z-mode (the low-frequency branch of the extraordinary mode). It is shown that in the cold plasma approximation, effective growth of the low-frequency waves due to an anisotropic photon beam can occur only for z-mode waves near the resonance frequency. In the application to pulsar eclipses, the cold plasma approximation may not be adequate and we suggest that when thermal effects are included, three-wave interaction involving low-frequency cyclotron waves (e.g. Bernstein modes) is a plausible candidate for pulsar eclipses
Seeing Degradation within the Anglo-Australian Telescope Dome
Authors: Ryan Sean G. , Wood Peter R.
Published: July 2016

Recent seeing measurements at the Anglo-Australian Telescope (AAT) point towards the thermal characteristics of the telescope itself, in particular the temperature difference between the mirror and the dome air, as the most important factor degrading the seeing, more so than the temperature difference between the inside and outside air. We present the findings, propose clarifying experiments, and discuss possible remedies. We set the realistic target for the AAT to achieve median seeing of 1·5″ rather than the current 1·8″.
HI in the Dusty Elliptical Galaxy NGC 5266
Authors: Morganti R. , Pizzella A. , Sadler E. M. , Bertola F.
Published: July 2016

Recent observations with the Australia Telescope Compact Array show that the elliptical galaxy NGC 5266 has a disk of neutral hydrogen extending to almost 10Re. This HI disk lies along the galaxy’s major axis, at right angles to the inner minor-axis dust lane. The geometry and kinematics of the gas will allow us to determine both the intrinsic shape of the stellar galaxy and the mass distribution. The mass-to-light ratio M/LB rises from about 2 in the central regions to ~12 at 9Re (H0 = 50km s−1 Mpc−1).
On the Statistics of AM Herculis Binaries
Authors: Wu Kinwah , Wickramasinghe Dayal T. , Li Jianke
Published: July 2016

The magnetic field and orbital period distributions of AM Herculis binaries are investigated. Our study shows that (i) there is a significant lack of very-high-field magnetic white dwarfs in binaries when compared with isolated white dwarfs, and (ii) the difference between the period distributions of AM Herculis binaries and other cataclysmic variable subclasses is statistically significant. These results imply that the evolution and the birth of AM Herculis binaries are different from those of other cataclysmic variables.
A Speculation into the Origin of Neutral Globules in Planetary Nebulae: Could the Helix’s Comets Really be Comets?
Authors: Gussie Grant
Published: July 2016

A novel explanation for the origin of the cometary globules within NGC 7293 (the ‘Helix’ planetary nebula) is examined, namely that these globules originate as massive cometary bodies at large astrocentric radii. The masses of such hypothetical cometary bodies would have to be several orders of magnitude larger than those of any such bodies observed in our solar system in order to supply the observed mass of neutral gas. It is, however, shown that comets at ‘outer Oort cloud’ distances are likely to survive past the red giant and asymptotic giant branch evolutionary phases of the central star, allowing them to survive until the formation of the planetary nebula. Some observational tests of this hypothesis are proposed.
Snapshot Imaging with the Australia Telescope Compact Array
Authors: Burgess A. M. , Hunstead R. W.
Published: July 2016

Radio snapshot imaging is an efficient observing method which allows several sources to be observed in the one session. Snapshot observing with the Australia Telescope Compact Array (ATCA) involves special difficulties, as the small number of antennas combined with the short total integration time leads to high sidelobe levels in the raw images. The images can be improved markedly by standard deconvolution techniques, but more care is required in their use because of the difficulty in distinguishing real emission from artefacts. This study, based on a set of snapshot observations of strong sources at 5 GHz, gives guidance on both the planning of observations and the data reduction. We show that snapshot imaging with the 6 km ATCA can achieve a dynamic range of 100–200:1 provided certain conditions are met, namely a peak flux density > 100 mJy, an angular size ≤ 30″ and an hour-angle coverage spanning at least six well-separated 5-minute cuts. When observing weak sources it is essential for calibration sources to be selected carefully and observed frequently.
Making the Figaro Data Reduction System Portable
Authors: Shortridge K. , Meatheringham S. J. , Carter B. D. , Ashley M. C. B.
Published: July 2016

The Figaro data reduction system was originally written for DEC VAXes running VMS, and little attention was paid to making it portable. Recently, however, a cooperative effort between the AAO, MSSSO, UNSW, the UK Starlink network and Caltech has resulted in a version for UNIX. This new version has been run under VMS and three different versions of UNIX. The files produced by any version may be read directly by any other version, although Figaro has a particularly complex file format which contains an extensible, self-defining, hierarchical structure of data items. This complexity has allowed the addition of error and quality data, as well as specific structures used, for example, for echelle data. Figaro is written mainly in Fortran (with numerous DEC extensions) but there is also a significant use of C. While C and Fortran are reasonably portable, the way one is called from the other is less portable and needs careful handling. Ports to other systems are possible, with effort; a Macintosh version is being considered.
The Astrophysical Value of Continuous Photometric Monitoring from the Antarctic Plateau
Authors: Viotti Roberto , Vignato Agostino , Nanni Domenico , Maceroni Carla , Badiali Massimo
Published: July 2016

Among the astrophysical researches which will largely benefit from observation from the Antarctic Plateau, we consider those which require high-quality, continuous, daylight, uninterrupted observation in the optical–near-IR region. The systematic study of the stellar micro-oscillations and surface activity of individual objects, as well as of stellar associations extended for periods of weeks, will make a fundamental contribution to our knowledge of stellar structure and will ultimately provide the physical parameters of the stars. A similar consideration applies for the short-period (a few hours to a few days) binaries, which include the W UMa contact binaries. These objects are subject to continuously varying light curves associated with surface activity and secular effects, which cannot be adequately studied from the currently available ground telescopes. Finally, the exceptional seeing and low background will allow the systematic search for and study of supernovae in clusters of galaxies at cosmological distances, which will improve our knowledge of the geometry of the Universe at z ~ 0·7–1.
Infrared Site Testing in Antarctica
Authors: Valenziano L.
Published: July 2016

Site testing campaigns in the mid-IR wavelength range have been carried out in Antarctica in the last two southern summer seasons. A description of the experimental apparatus and some preliminary results are presented in this work. Future plans are also discussed.
Sydney Observatory and Astronomy Teaching in the 90s
Authors: Lomb Nick
Published: July 2016

Computers and the Internet have created a revolution in the way astronomy can be communicated to the public. At Sydney Observatory we make full use of these recent developments. In our lecture room a variety of sophisticated computer programs can show, with the help of a projection TV system, the appearance and motion of the sky at any place, date or time. The latest HST images obtained from the Internet can be shown, as can images taken through our own Meade 16 in telescope. This recently installed computer-controlled telescope, with its accurate pointing, is an ideal instrument for a light-polluted site such as ours.
Millimetre Astronomy and Antarctica
Authors: Burton Michael
Published: July 2016

The thermal emission from a cold, dense molecular cloud peaks in the far IR, and the spectrum is rich in molecular lines in the submillimetre and millimetre bands. Observation of these bands is hindered, however, by atmospheric water vapour, which absorbs the incoming radiation. Ground-based mm observations from Australia, where the atmospheric water vapour content typically contains ~10 mm precipitable (ppt) H2O, can only probe a few of the molecular transitions from the heavier molecules, such as CO, CS, HCO+ and HCN. Sub-mm observations would enable the higher rotational lines from many of these molecules to be studied, and open up other spectral features to scrutiny, such as the lines from hydrides (e.g. CaH, NH, SH) and neutral carbon at 370 and 610 μm. However, they cannot be made from Australia. While sites such as Mauna Kea, which has ~1 mm ppt H2O on the best days, open the sub-mm band to partial viewing, their utility is limited in comparison to the opportunities possible from the Antarctic Plateau. Here the column of H2O drops to 100–250 μm.
Chemical Abundances and Isotope Ratios in Molecular Clouds
Authors: Hunt M. R.
Published: July 2016

A program to observe millimetre-wave molecular transitions in a number of southern-sky molecular clouds is under way. Molecular clouds in both the Galaxy and the Magellanic Clouds are included in the sample. The aim of the program is to build a body of observational data which can be used to derive molecular abundances in southern-sky molecular clouds.
Gravitational Lensing of Millisecond Pulsars
Authors: Walker Mark A.
Published: July 2016

Gravitational lensing can significantly magnify the images of astrophysical sources, but only if the source lies within the Einstein ring of the lens. In consequence the chance of any Galactic star magnifying a more distant source is extremely small—much less than one in a million. However, the extra light travel time (‘Shapiro delay’) introduced by the presence of a lens can be large even when there is negligible effect on the image magnification, and as the relative positions of source and lens change so does the delay. In this paper we quantify these changes and the corresponding influence on apparent timing properties of pulsars. While the total Shapiro delay can be large, it is the temporal variations in this quantity which are measurable with pulsar timing. We find that the magnitude of the expected delay variations is too small to be detectable except during strong lensing events, which are extremely rare. Even in the case of a high-velocity pulsar in the Galactic Plane, the stochastic Shapiro delay is typically expected not to have a substantial influence on the timing properties. In consequence the viability of a pulsar-based time standard is not adversely affected by gravitational lensing.
The Parkes 21 cm Multibeam Receiver
Authors: Staveley-Smith L. , Wilson W. E. , Bird T. S. , Disney M. J. , Ekers R. D. , Freeman K. C. , Haynes R. F. , Sinclair M. W. , Vaile R. A. , Webster R. L. , Wright A. E.
Published: July 2016

Several extragalactic HI surveys using a λ21 cm 13-beam focal plane array will begin in early 1997 using the Parkes 64 m telescope. These surveys are designed to detect efficiently nearby galaxies that have failed to be identified optically because of low optical surface brightness or high optical extinction. We discuss scientific and technical aspects of the multibeam receiver, including astronomical objectives, feed, receiver and correlator design and data acquisition. A comparison with other telescopes shows that the Parkes multibeam receiver has significant speed advantages for any large-area λ21 cm galaxy survey in the velocity range range 0–14000 km s−1.
William Edwin James: Designer and Maker of Astronomical Optics
Authors: Bolton H. C. , Coates D. W.
Published: July 2016

We give an account of the life and work of William James, including his many contributions to astronomy in Australia mainly through his skill in designing, figuring and testing aspheric surfaces.
Time-Dependent Magneto-Convection with Hexagonal Planform
Authors: Lopez J.M. , Murphy J.O.
Published: July 2016

High-resolution observations indicate that very strong, small scale magnetic fields in the solar photosphere are concentrated into ropes which emerge through it. The scale of these ropes is only a few hundred kilometres across (Stenflo 1976) and their strength is estimated to vary between 1,000 and 2,000 G (Harvey 1977). These features are closely related to photospheric granular convection. The flux is observed as X-ray bright spots and sheet-like crinkles in the dark intergranular lanes, and is buffeted and shifted about by the granules (Dunn and Zirker 1973). Further, the crinkles can be resolved into separate features which outline small micropores as though a flux sheet at the end of a convection cell has separated into several isolated tubes (Galloway and Weiss 1981).
Recent Optical Observations of the X-Ray Source H0139-68; an AM-Herculis Type Binary System
Authors: Pickles A.J. , Visvanathan N.
Published: July 2016

The soft X-ray source HO 139-68 was originally detected with the low energy detectors of the HEAO A-2 experiment, and confirmed by later IPC observations (Agarwal et al. 1981). The X-ray observations show flux variations in the 0.15 – 0.4 keV band of a factor of two, or timescales of a few hours, with evidence for short time-scale flickering. Following communication of the source position to us by Agarwal and Riegler, we obtained time-resolved optical spectrophotometry of a star close to the X-ray position, using the IDPCA on the MSO 1.9m telescope. The spectrophotometry and later polarisation observations confirm the optical identification and that the source is an AM-Herculis type binary system, with a late type dwarf secondary overflowing its Roche lobe in a magnetically constrained funnel onto a magnetic white dwarf (WD) primary (Visvanathan and Pickles 1982).
A Timeless, Boundless, Equilibrium Universe
Authors: Reber Grote
Published: July 2016

For more than half a century the theory that the universe is expanding has dominated cosmology. All current cosmological theories, from the various Big Bang models to the various Steady State models, explicitly assume an expanding universe. The evidence in favour of an expanding universe is purely circumstantial, and is based on a “sheer assumption”, (Hubble 1936a) that red-shifts in the light received by an observer on Earth from distant objects are caused by relative motion and hence may be interpreted as Doppler shifts. Hubble (1936b) continues: “…the ever expanding model … seems rather dubious”, and “On the other hand, if the recession factor is dropped, if red-shifts are not primarily velocity-shifts, the picture is simple and plausible. There is no evidence of expansion and no restriction of time-scale, no trace of spatial curvature and no limitations of spatial dimensions.” (Hubble 1936c). These statements are as true today as they were in 1936.
Solar Flares: Implications of the Circuit Model (Invited Paper)
Authors: Melrose D. B.
Published: July 2016

A review is given of recent developments in the interpretation of the structure and heating of the solar corona, and of solar flares. An electric circuit model for a flaring magnetic loop is introduced, and used to discuss the closure of the current pattern. It is argued that cross-field current flow cannot be set up after a flux tube has emerged above the photosphere. The energy dissipated in a flare is attributed to a change in the inductance of the flaring loop, with the current remaining approximately constant. Emphasis is placed on the value of the resistance of the flaring loop, and on the associated inductive timescale.
The Galactic Force Law
Authors: Flynn Chris
Published: July 2016

We describe a survey of metal rich K-giants at the SGP, and show how they can be used as a simple isothermal tracing population to derive the local density of matter and the component of acceleration Kz perpendicular to the galactic plane.
TV Rate Readout Unit for Two-dimensional CCDs
Authors: Mitchell P. , Ollier E.
Published: July 2016

A simple circuit has been designed for reading out at TV rate the two-dimensional CCD on the Automated Patrol Telescope. Because it is controlled by a programmable Cathode Ray Tube Controller integrated circuit it is very flexible and applicable to frame transfer CCDs having a wide range of formats.
A Search for 43.122 GHz SiO Emission from Symbiotic Stars
Authors: Hall P. J. , Wark Robin M. , Wright Alan E.
Published: July 2016

During the second half of 1986 tests were made of a new Q-band (43 GHz) receiver designed for the Parkes radio telescope. As part of the trial observation program 12 symbiotic stars were examined for SiO maser emission. No significant new emission was detected from any of the candidates, although several previously known SiO sources (including one symbiotic star) were confirmed. We conclude that potential SiO maser action near the Mira star in most symbiotic systems is prevented by the presence of the hot companion star.