bluuebunny/crossref_metadata_2025 huggingface dataset:
Distribution of H2CO Absorption at 4.8 GHz towards M17
Authors: Gardner F. F. , Whiteoak J. B.
Published: July 2016

The complex consisting of the bright HII region M17 (G15.0-0.7) and its associated molecular cloud is well known as a region of active star formation which contains an abundance of many different molecules (see e.g. Lada 1976). For H2CO, observations of the 110 – 111 transition at 4.8 GHz towards the HII region show an intense narrow absorption feature with a radial velocity near + 24 km s−1 superimposed on weak absorption which extends to below +10 km s−1 (Whiteoak and Gardner 1970). According to Whiteoak and Gardner (1974) the latter consists of several features centred at the velocities of +4.7, + 10.4, + 17.9 and +20.3 km s−1. Lada and Chaisson (1975) mapped the absorption around M17 with a 6′ .5 arc beam and concluded that the broad component was associated with the obscuring dust cloud near the HII region while the narrow feature occurred in a foreground cloud. In this paper we present observations made with higher angular resolution and higher sensitivity; they define better the H2CO distribution and its relationship with the extended CO cloud near M17 (Elmegreen et al. 1979).
A CO Survey of the Southern Galactic Plane
Authors: McCutcheon W. H. , Robinson B. J. , Whiteoak J. B.
Published: July 2016

Millimetre-wave emission from the CO molecule has proven to be an extremely useful probe of the cold, dense clouds of molecular hydrogen in the Galaxy. Previous studies of the large-scale distribution of CO in the galactic plane (Scoville and Solomon 1975; Burton et al. 1975; Bash and Peters 1976; Burton and Gordon 1978; Solomon et al. 1979b; Cohen et al. 1980) have all been of the northern hemisphere and primarily at longitudes 0° ≤ l ≥ 80°. These studies have revealed the striking characteristic that the CO, and by implication molecular hydrogen clouds, are concentrated in a ring extending from 4 to 8 kpc from the galactic centre. This is in sharp contrast to the atomic hydrogen distribution, which is fairly constant over the extended region from 4 to 13 kpc but correlates well with other Population I indicators.
Survey of NH3 in the Southern Hemisphere
Authors: Scalise E. , Schaal R. E. , Bakor Y. , Boas J. W. Vilas , Myers P. C.
Published: July 2016

Ammonia was searched in the direction of 46 sources placed in the southern hemisphere where H2CO or H2O was detected previously. Observations were carried out at Itapetinga Radio Observatory, Atibaia, Brazil using a 13.7 m paraboloid. The receiver used for these observations had a K-band ruby travelling wave maser as a preamplifier and the system temperature ranged from 250 to 300K. All sources were observed at least twice, each observation lasting for 30 minutes. The filter bank used consisted of 47 contiguous channels with 100 kHz bandwidth. Results are presented on Table 1 — Positive results and Table 2 — Negative results.
Temperature Effect in Zero-Point Drift
Authors: Kviz Z.
Published: July 2016

The relationship between the observed magnitude of a star and the air-mass takes the shape of a loop. These loops are caused by the zero-point drift of the photometer in use and by the variations of the atmospheric extinction taking place during the observation (Kviz 1979). From observations where the temperature drift of the photometer and of the photomultiplier were recorded, it is evident that the sense of the loops is correlated with the physical temperature of the photo-multiplier. Measurements have been made with the Swiss telescope and the 7-colour Geneva photometer P 7 using pulse counting with PM tube EMI9798 — described in Burnet (1976) and Burnet, Rufener (1979) — at La Silla, Chile.
Environs of HII Regions
Authors: Roger R. S.
Published: July 2016

It is generally agreed that early-type stars, and hence their HII regions, appear to develop preferentially in dense concentrations within molecular clouds. These parent molecular clouds owe their existence in two ways to the dust grains in the interstellar gas, a component which comprises about 1% by mass. First, dust grains provide stable surfaces upon which hydrogen atoms can come together to form molecules. Then, once formed, the molecules are protected in cloud interiors by dust absorption of the dissociating ultraviolet radiation which pervades the low-density interstellar medium.
The Influence of the Magnetic Boundary Conditions on the Nature of Astrophysical Convection
Authors: Lopez J. M. , Murphy J. O.
Published: July 2016

The relevance of the results for the total heat energy transported across a fluid layer by convective motions, obtained from the time integrations of the set of non-linear partial differential equations for hydromagnetic convection, has already been designated in a previous contribution (Lopez and Murphy 1982). Some differences in the form of the boundary conditions adopted for the magnetic field disturbance, H, have been noted in other publications where the interaction of convection and a magnetic field has also been considered. The solutions of the time-dependent equations, referenced above, illustrate that the magnetic boundary conditions have a determining role in the resultant convective state for some ranges of values in parameter space.
The Space Density of Hot White Dwarfs
Authors: Reid Neill , Wickramasinghe D.T. , Bessell M.S.
Published: July 2016

The space density of degenerate stars is an important parameter in Galactic Structure studies, not only because white dwarfs represent a significant fraction of the local mass density, but also because they act as tracers of the history of star formation (see e.g., Bessell 1978). Combining the present day luminosity function with theoretical cooling tracks allows constraints to be set on the birth rate of main sequence progenitors. However, since white dwarfs are intrinsically low luminosity objects, observational studies are hampered by difficulties in defining complete samples large enough to have statistical significance. This paper discusses preliminary results from one method of tackling this problem.
The Elliptical/Spiral Pair of Galaxies NGC 5090/5091
Authors: Smith R.M. , Bicknell G.V.
Published: July 2016

PKS 1318-43 was first identified with the elliptical galaxy NGC 5090 by Ekers (1969) in the Parkes catalogue. Schilizzi and McAdam (1975) mapped the source with 2.9 arcmin resolution at 408 MHz using the Mills Cross, resolving the source into an extended double structure approximately 15 arcmin in extent at p.a. 36°. Schilizzi (1975) also noted a possible optical link with an edge-on spiral (NGC 5091) ~75 arcsec to the south-east. Figure 1 shows a print of the two galaxies taken from the UK Schmidt J survey film. During 1980, in collaboration with K. J. Wellington, RMS mapped the source at 1415 MHz with the Fleurs Synthesis Telescope (FST, Christiansen 1973).
Illuminating Incidents in Antipodean Astronomy: The Mysterious Tasmanian Comet of December 1883
Authors: Orchiston Wayne
Published: July 2016

Australian astronomers have a proud history of comet-discovery, beginning with Rumker of Parramatta Observatory in 1824 (Baracchi 1914), and culminating with the outstanding achievements of Bill Bradfield of Adelaide. In the intervening one hundred and fifty years there have been a number of other notable comet-hunters and comet-observers, the most successful being John Tebbutt (see Orchiston 1981, 1982a, 1982b), Walter Gale, David Ross, and J. F. Skjellerup. Comets discovered by these Australian astronomers, and others, are listed in Marsden’s 1982 Catalogue of Cometary Orbits.
A Catalogue of Symbiotic Stars
Authors: Allen David A.
Published: July 2016

Mare than 100 symbiotic stars are now known. A catalogue of them, complete to 1984 January 1, is presented. Finding charts are given for all examples, and optical spectra for the majority. A table summarises the observational material at X-ray, ultraviolet, infrared and radio wavelengths.
Megalithic Observatories in Britain: Real or Imagined?
Authors: Norris R. P.
Published: July 2016

Over the last two decades there has been an accumulation of exciting evidence that appears to show that, as early as 5000 years ago, people in Britain were making precise observations of the Sun, Moon, and stars, and studying small perturbations in the lunar motion. Structures such as Stonehenge, and the s thousands of other megalithic sites in Britain, are then seen as prehistoric observations. Within these, data would be (accumulated to enable the prediction of celestial phenomena such as eclipses, and allow the construction of a calendar. Recently however a small number of rigorous statistical studies of the sites have cast doubt on the astronomical hypotheses, and have posed the question of whether some of the support for these hypotheses has been generated by well-intentioned but over-enthusiastic selections of chance alignments. In this review, the arguments and counter arguments are presented and examined, and we see what can be salvaged from the astronomical hypotheses after the statistical smoke has cleared.
Two-Photon Cyclotron Emission in Accretion Columns
Authors: Kirk J. G. , Melrose D. B. , Peters J. G.
Published: July 2016

Cyclotron lines have been observed in the X-ray spectra of two pulsed sources: Her X-1 (Trümper et al. 1978) and 4U 0115 + 63 (Wheaton et al. 1979). The generally accepted model for these objects involves an accretion flow from a companion star in a close binary system onto small regions close to the magnetic poles of a strongly magnetized neutron star. Immediately above the surface, matter is confined in an accretion column by the magnetic field.
Dynamics of Clusters of Galaxies
Authors: Carter D. , Teague P. F.
Published: July 2016

Clusters of galaxies appear to contain much more mass than just that of the galaxies which provide most of their optical luminosity. There are two important ways to investigate the structure of their gravitational potential wells, firstly by an analysis of the radial velocities of the cluster galaxies, and secondly by a study of the X-ray emission from the hot gas which forms part of the intra cluster medium. We present new samples of radial velocity data for three clusters, and discuss some simple types of models of the X-ray sources.
An Analysis of the Distribution of Faint Galaxies at the South Galactic Pole
Authors: Dodd R. J. , MacGillivray H. T.
Published: July 2016

The distribution of faint galaxies in a deep sample, down to a limiting magnitude of B ~ 21.5 in a region of some 30 square degrees of sky at the South Galactic Pole, is investigated. The sample was obtained from objective measurements made with the COSMOS automatic plate-scanning machine. The two-point angular correlation function shows positive correlation on scales out to ~1.5° and thereafter positive correlations on scales ~ 2.5° and ~ 5° indicating the presence of clustering in this sample on linear scales out to ~ 8h-1 Mpc and at ~ 13h-1 and ~ 27h-1 Mpc. On application of an algorithm for the detection of filamentary structure in the distribution of the galaxies, a negative result is obtained.
IC4553: Masers Around an Active Galactic Nucleus
Authors: Norris R. P.
Published: July 2016

The galaxy IC4553 (Arp 220) is a peculiar galaxy having a redshift of 0.02. It has been variously described as consisting of a symbiotic pair of galaxies, as having a highly peculiar pair of nuclei, or as consisting of a nucleus bisected by a dust lane. In addition, it exhibits OH maser emission which is both the most intrinsically luminous (by four orders of magnitude) and the most distant yet detected. MERLIN observations of the continuum emission at 18 cm show a core-dominated triple structure, probably indicating jets about 500 pc in extent. The integrated OH maser emission has an identical spatial structure, but when this structure is examined as a function of frequency across the line it is found that each spatial component has its greatest intensity at a different frequency. This is interpreted as amplification of the radio continuum image by the OH masers. The change in spatial structure across the emission line is caused by the velocity structure of the OH gas. Measurements of the velocities of these masers therefore reveal the kinematics of the central part of the galaxy. Optical and infrared observations indicate that at the centre of the galaxy is a Seyfertlike active galactic nucleus, which appears double on optical plates only because of the dense dust lane which bisects the nuclear region. This indicates that IC4553 is an edge-on Seyfertlike galaxy. The OH maser radiation is a result of stimulation of the OH along the line of sight within the galactic plane by the strong far-infrared radiation from the nucleus. No abnormal conditions are required for this process, so IC4553 may not be unique, and we should search for OH maser emission in other edge-on active galaxies.
Steep-Spectrum Radio Sources in Clusters of Galaxies—The Southern Sample
Authors: Slee O. B. , Reynolds J. E.
Published: July 2016

It is well established (e.g. Slee et al. 1983) that radio galaxies near the centres of rich clusters of galaxies tend to have steeper radio spectra than field radio galaxies. The fact that the sources with the steepest spectra occur in clusters that are highly luminous X-ray emitters has generally been interpreted in terms of the confining influence of a hot (~108 K), relatively dense (10-2 to 10-3 electrons cm-3) intra-cluster gas; the confined relativistic plasma then preferentially loses its high-energy electrons through synchrotron and inverse Compton losses, resulting in a steepening of the radio spectrum. A more detailed review of the evidence for this process is given by Robertson (1983).
The Sensitivity of the V/VmTest to Uncertainties in Observed Parameters
Authors: White G. L.
Published: July 2016

Schmidt (1968) and Rowan-Robinson (1968) developed a simple and concise test for the uniformity of the distribution of quasars (QSOs) based on QSO luminosity and occupied volume.
Search for Light Flashes from a Gamma Ray Burst Source
Authors: Fenton K. B.
Published: July 2016

Bursts of gamma rays lasting from a fraction of a second to several seconds have been observed by spacecraft since 1967 (Klebesadel et at. 1973). Events with fluxes in excess of 10−4 erg cm−2 s−1 are seen at the rate of several per year for gamma ray detectors with an energy threshold of ˜50 keV. The sources of these bursts remain unidentified and the mechanism(s) responsible for the production of the gamma rays remain(s) in the realm of conjecture. (For a review see Ramaty and Lingenfelter 1982).
The Observatory At The Lands Department Building Sydney
Authors: White Graeme L.
Published: July 2016

The Lands Department Building in Sydney is situated on the block bounded by Bridge Street, Gresham Street, Bent Street and Loftus Street. The northern (Bridge Street) end is surmounted by a small copper dome.
Non neutral Plasmas in the Laboratory and Astrophysics
Authors: Michel F. Curtis
Published: July 2016

Recent laboratory experiments have confirmed theoretical expectations that the aligned rotator model (Goldreich and Julian 1969) does not function in the way originally expected, if at all. These experiments confirm that the nonneutral (completely charge-separated) plasma is isolated into finite regions, which in the case of the magnetosphere about an aligned rotator means in general that there is no plasma from the neutron star to be found at the light-cylinder. Hence the interesting pulsar-like properties originally postulated no longer follow.
FST Observations of NGC 4945 and the Circinus Galaxy
Authors: Whiteoak J. B. , Bunton J. D.
Published: July 2016

The Fleurs synthesis telescope, which provides 20 arcsec resolution at 1.4 GHz, was used to map the continuum emission in NGC 4945 and the Circinus galaxy. Both objects have prominent small-diameter radio nuclei, containing 50% to 75% of the total intensity, superimposed on extended emission associated with the outer regions of the galaxies. The scale of the nuclei, together with the large velocity widths of the associated spectral-line profiles, are not unlike those encountered in the central region of the Galaxy.
Fragmentation in Collapsing Magnetic Gas Clouds–Non-Uniform Initial Fields
Authors: Phillips G. J.
Published: July 2016

It is widely believed that stars form from collapsing interstellar clouds. However, molecular clouds typically contain of the order of 103 solar masses. Thus a mechanism is required that allows a collapsing cloud to fragment into a number of collapsing stellar sized sub-condensations. The early work was based on a virial theorem approach—defining a critical mass a cloud must exceed in order for its gravitational force to overcome the resistive thermal, rotational and magnetic forces, thus allowing the cloud to collapse. This critical mass is analogous to the Jeans mass for non-rotating, non-magnetic clouds. It is thought that a cloud containing several critical masses may collapse into several sub-condensations. Further, it is thought that the galactic magnetic field will cause the critical mass to decrease as the cloud collapses, allowing the cloud to fragment into a number of sub-condensations. The critical mass decreases as the cloud flattens down the field lines (since Mcrit ∝ B3/ϱ2 and B ∝ ϱk, K < ⅔ for non-isotropic collapse).
Rapidly Rotating Core-Collapse Models
Authors: Thompson M. C.
Published: July 2016

Very few (if any at all) three dimensional models of the final evolutionary stages of a star’s life have appeared in the literature. Such models may be important if the stellar core maintains sufficient rotational energy during it’s lifetime so that when collapse finally occurs, the increase of rotational energy to gravitational energy, may lead to a non-axisymmetric instability.

A sequence of core collapse models with decreasing rotation rate is considered. These models were calculated using a three dimensional, post-Newtonian, hydrodynamical, numerical code. The results show that for high precollapse rotational energies the core can become unstable resulting in the formation of what resemble ‘spiral arms’. Unfortunately, because of limits on computer time, the calculations had to be discontinued shortly after this development occurred.
Postscript on “Features of the Chandlerian Nutation”
Authors: Lilley F.E.M.
Published: July 2016

Henry Abraham died on 9 December 1985. A few days earlier, he explained to me the work he had been doing in recent years, and gave me responsibility for his documents and notes. Amongst them were the manuscript for the above paper, prepared about 1979 but not submitted for publication then, and meticulous and extensive notes which examine further the questions raised by the paper. It has seemed to me to be appropriate to submit for publication the above paper as he wrote it, and to add a summary of his subsequent work as I interpret it.
Asymmetric X-ray Pulsar Beam Emission
Authors: Padden Whayne E. P. , Storey Michelle C.
Published: July 2016

Many of the X-ray pulsars for which X-ray lightcurves have been presented in the literature exhibit asymmetric emission beams. We postulate the existence of an off-centre magnetic dipole field embedded in the rotating neutron star and show that such a field leads to varying rates of matter transfer between an accretion dise and the neutron star surface, over a rotation period. Assuming that the accretion rate onto the surface is simply related to the luminosity, we show that most of the observed asymmetries can be accounted for by this mechanism.
Integrability of Motions in Galactic Potentials
Authors: Cleary Paul
Published: July 2016

The dynamics exhibited by systems, such as galaxies, are dominated by the isolating integrals of the motion. The most common are the energy and angular momentum integrals. The motions in a system with a full complement of isolating integrals are regular, that is, periodic or quasi-periodic. Such a system is integrable. If there is a deficiency in the number of integrals, then the motions are chaotic. There is a fundamental quantative difference in the motion, depending on the number of integrals. A technique, called Generalised Painlevé analysis, based on complex variable theory allows the user to determine if a system is integrable. Two new integrable cases of the Henon-Heiles system are presented, bringing the total number of such integrable potentials to five. It is highly probable that there are no further integrable cases of the Henon-Heiles potential. Five cases of the quartic Verhulst potential, defined by certain restrictions on the coefficients, which are found to be integrable are summarised.
Use of a Surface Polarizer to Reduce the Spectral Baseline Ripple of the Parkes Telescope
Authors: Williams D. R. , Thomas B. MacA.
Published: July 2016

Baseline ripple measurements are of two general kinds, those associated with on-source mechanisms and those with off-source mechanisms (Poulton 1974; Morris 1974). We are here principally concerned with on-source baseline ripples, which occur when a strong continuum radio source is present in the beam. The ripples are particularly conspicuous (Padman 1977, 1978) with a large instrument, such as the Parkes 64-m telescope, where the ripple period is rapid. Here baseline uncertainty becomes especially severe for the detection and study of wide lines, such as the H/He complex and the formamide multiplet near 1.54 GHz. Off-source baseline ripples also occur because of other effects, but in principle they can be removed by subtracting a reference-region spectrum taken while tracking the telescope over the same hour-angle range at the same declination under stable conditions. Improvement of the off-source baseline ripple which arises from stray radiation would also be expected to result from the technique described here.
A High Resolution Study of Tidal Interaction in Stars
Authors: Gingold R. A. , Monaghan J. J.
Published: July 2016

When two stars are in orbit about each other, tidal forces cause an exchange of energy and angular momentum between the orbital motion and the fluid motion of each star about its own centre of mass. The orbit is progressively altered, and one or both stars may be catastrophically disrupted.
Aspects of the Collapse of Compact Objects
Authors: Gingold R. A. , Monaghan J. J.
Published: July 2016

Misner Thorne and Wheeler (1973), (page 629) suggested that a freshly formed White Dwarf star of several solar masses would, if slowly — rotating, collapse to form a neutron star pancake which would become unstable and eventually produce several, possibly colliding, neutron stars.
Evidence of Directivity of Solar Type III Radio Burst Storm Emission
Authors: Wright C. S.
Published: July 2016

Solar type III radio bursts often occur for prolonged periods (≳ 1 hour) with small time intervals (≲ 1 minute) between bursts. Such phenomena usually are confined to decametre wavelengths (frequency ≲ 100 MHz) and are called ‘type III storms’ (e.g. Stewart and Labrum 1972).
Realistic Line Models for Pulsating B Stars
Authors: Stamford P. A. , Watson R. D.
Published: July 2016

Spectral line profiles in pulsating stars are affected by the interplay of a number of velocity fields. In addition to the basic velocities associated with the pulsation mode, the complications of stellar rotation, atmospheric velocity gradients, stellar winds and varying scales of turbulence may also be present. Initial modelling for line profiles in variables assumed a constant ‘intrinsic profile’ which was integrated over the limb-darkened stellar disk. This approach has been used even in recent work for nonradial pulsations (Stamford and Watson 1977; Kubiak 1978) because of computational ease. Employing an LTE analysis to predict centre-to-limb profile variations, which are then integrated over the disk, represents an improvement on this. This has been done, for example, by Parsons (1972) for radial pulsations in cepheids and by Smith (1978) for nonradial oscillations in B stars. Mihalas (1979) has recently made an even more detailed examination of profiles in expanding atmospheres which involved consideration of velocity gradients, departures from LTE and rotation.
Further Studies of the Cosmic Ray Flare of November 22, 1977
Authors: Fenton A. J. , Fenton K. B. , Humble J. E.
Published: July 2016

The ground level event (GLE) observed on November 22, 1977, is of interest because of the spread of onset times observed by various cosmic ray neutron monitors. Previous reports (Fenton, Fenton and Humble 1978, 1979) have discussed this matter without being able to reach definite conclusions. We have now obtained data from a further seven neutron monitors, and also some from the Imp 8 spacecraft. These data combine to suggest that the event may have been more complex than we initially supposed.
Rigidity Dependence of Forbush Decreases
Authors: Duldig M. L. , Humble J. E.
Published: July 2016

Ina recent paper, Lockwood et al. (1991) have used IMP spacecraft and Neutron Monitor data to consider the rigidity dependence of three large Forbush Decreases over the energy range 50 MeV to 30 GeV. Some of their conclusions are extrapolated to higher energies.

In an earlier paper (Duldig, 1987a), one of us discussed the need to consider the presence of isotropic intensity waves when determining the Forbush Decrease spectrum at energies up to a few hundred GeV. Lockwood et al.’s conclusions are discussed in the light of these results.
An Infrared Imaging Survey of the ρ Oph and R CrA Dark Cloud Cores
Authors: Burton Michael
Published: July 2016

We report on an initial survey of the cores of the Rho Ophiuchus and R Coronae Australis clouds, made with the AAT’s new IR array camera, IRIS. No turnover is seen in the initial luminosity function for ρ Oph to the sensitivity limit of the survey. Some implications for the low mass end of the initial mass function are discussed.
Does Gravity Rule the Universe?
Authors: Mathewson Donald S.
Published: July 2016

The initial results of a southern sky survey of the peculiar velocities of 1355 spiral galaxies by a group at Mount Stromlo and Siding Spring Observatories (MSSSO) are discussed against the background of past work in this area. The most important result is that the Great Attractor does not exist; rather, there is bulk flow relative to the cosmic microwave background (CMB) of amplitude 600 km s−1 and scale greater than 130 h−1 Mpc in the Supergalactic plane. This is generated by the assumption that the CMB dipole is Doppler induced by our Galaxy moving at 622 km s−1 relative to the CMB. This may be incorrect, in which case there is no bulk flow and the radiation dipole is cosmological in origin with important implications for the early Universe.
Near-infrared Imaging and Spectroscopy of Centaurus A
Authors: Meadows Vikki , Allen David
Published: July 2016

We present near-infrared images and spectra of the peculiar radio galaxy Centaurus A. The images reveal extended emission regions at the longer wavelengths and show colours characteristic of reddened starlight. We believe we are seeing stars within the warped disc of Cen A, which are obscured in the optical by dust. Both images and spectra indicate the presence of a compact core, whose colours are much redder than those of the surrounding stars. In the spectrum of the core, detections have been made of [Fe II] 1.644 μm, H2 2.122 μm and Br γ. These lines appear to peak on the nucleus and their presence and width suggest starburst activity.
Hot Bottom Burning in a 5 M⊙ Model
Authors: Lattanzio John C.
Published: July 2016

This paper presents recent stellar evolutionary calculations of the Asymptotic Giant Branch evolution of a 5M⊙ model. It is found that temperatures at the base of the convective envelope reach up to almost 100 million degrees, high enough for much nucleo-synthesis to occur. Some implications are discussed briefly.
Is Alfvén’s Critical Ionization Velocity Important at the Galactic Centre?
Authors: Nicholls Jennifer
Published: July 2016

If the relative velocity between a plasma and a molecular cloud impinging on it exceeds the Alfvén critical ionization velocity, then the surface of the molecular cloud can be ionized. This phenomenon has been used to model some of the ionized regions at the Galactic Centre. A review of the mechanism behind Alfven’s critical ionization phenomenon is presented here, and its use at the Galactic Centre is discussed.
The IAU Thesaurus for Improved On-line Access to Information
Authors: Shobbrook R.M. , Shobbrook R.R.
Published: July 2016

There is a need for standardised terminology in the field of astronomy. A project on behalf of the International Astronomical Union has been undertaken by astronomy librarians to compile a thesaurus for inputting to and accessing computer database systems.
The Ellery Lecture 1993: Pulsars—Setting the Standard
Authors: Manchester R. N.
Published: July 2016

Over 600 pulsars are now known, almost all of which lie in our Galaxy. Most pulsars have periods between 0 · 1 and a few seconds, but a very important sub-class, the ‘millisecond’ pulsars, have much shorter periods. Millisecond pulsars are often in a binary orbit with another star, suggesting that their short periods are a result of accreting mass from the companion star. They are also extraordinarily good clocks, with a stability comparable to that of the best atomic clocks. This combination of extreme period stability and binary motion has led to some very important results, including the first observational evidence for gravitational radiation and the first evidence for extra-solar planetary systems. It is probable that pulsars will be used to define the long-term standard of terrestrial time. A search of the southern sky using the Parkes radio telescope has found several millisecond pulsars which will make an important contribution to these precision-timing programs.
Audible Fireballs and Geophysical Electrophonics
Authors: Keay Colin S. L.
Published: July 2016

The long-standing enigma of audible sound production simultaneous with the distant flight of large meteor fireballs is becoming increasingly well understood. Utilising Keay’s model linking the production of ELF/VLF electromagnetic radiation with turbulence in the fireball’s plasma trail, it has proved possible to adapt Ceplecha’s fireball model to include the criteria for turbulence and the consequent production of electrophonic sounds, yielding an excellent match with observations. It is becoming apparent that other geophysical phenomena also have the capacity to produce electrophonic sounds. These include aurorae, lightning and earthquakes.
The Cosmology Distinction Course in NSW
Authors: Hollow Robert P. , McAdam W. B. , O’Byrne J. , White Graeme L. , Holmes R. , Webb J. K. , Allen L. R. , Zealey W. J. , Hafner R.
Published: July 2016

The Cosmology Distinction Course is a new one-year course to be introduced for Year 12 candidates in the 1994 Higher School Certificate examinations in NSW. It is one of three challenging courses of study that will enrich the HSC for talented students who accelerate and complete part of the HSC one year early. The courses will be taught through distance learning and will include residential seminars. They will be implemented on behalf of the Board of Studies by Charles Sturt University and the University of New England.

The Cosmology Course is organised into nine modules of course work covering historical and social aspects of cosmology, observational techniques, key observations and the various models developed—Newtonian, de Sitter, Friedmann, Lemaitre, steady-state, quasi-steady-state and big bang. Assessment will be through assignments, exams and a major project.

As the first Distinction Course in a scientific area, the Cosmology Course represents an exciting and important educational initiative that needs the cooperation of NSW astronomers and, in return, promises to benefit the astronomical and general scientific community in Australia.
The Sydney University PAPA Camera
Authors: Lawson Peter R.
Published: July 2016

The Papa camera is a photon-counting array detector that uses optical encoding to locate photon events on the output of a microchannel plate image intensifier. The Sydney University camera is a 256×256 pixel detector which can operate at speeds greater than 1 million photons per second and produce individual photon coordinates with a deadtime of only 300 ns. It uses a new Gray coded mask-plate which permits a simplified optical alignment and successfully guards against vignetting artifacts.
Structure of Inhomogeneous Accretion Shocks
Authors: Wu Kinwah
Published: July 2016

We investigate the structure of inhomogeneous accretion shocks in magnetic white dwarfs. We find that bremsstrahlung cooling still plays an important role in determining the structure of the post-shock region, even when its cooling timescale is much longer than the cyclotron cooling timescale at the shock surface. Our calculations also show that a substantial amount of the accretion energy is dissipated at the base of the post-shock region through emission of bremsstrahlung radiation.
The Scientific Potential for Astronomy from the Antarctic Plateau: A Report prepared by the Australian Working Group for Antarctic Astronomy
Authors: Burton Michael , Aitken D. K. , Allen D. A. , Ashley M. C. B. , Burton M. G. , Cannon R. D. , Carter B. D. , DaCosta G. S. , Dopita M. A. , Duldig M. L. , Edwards P. G. , Gillingham P. E. , Hall P. J. , Hyland A. R. , McGregor P. J. , Mould J. R. , Norris R. P. , Sadler E. M. , Smith C. H. , Spyromilio J. , Storey J. W. V.
Published: July 2016

Our knowledge of the universe comes from recording the photon and particle fluxes incident on the Earth from space. We thus require sensitive measurement across the entire energy spectrum, using large telescopes with efficient instrumentation located on superb sites. Technological advances and engineering constraints are nearing the point where we are recording as many photons arriving at a site as is possible. Major advances in the future will come from improving the quality of the site. The ultimate site is, of course, beyond the Earth’s atmosphere, such as on the Moon, but economic limitations prevent our exploiting this avenue to the degree that the scientific community desires. Here we describe an alternative, which offers many of the advantages of space for a fraction of the cost: the Antarctic Plateau.
Radial and Latitudinal Gradients in Galactic Cosmic Rays
Authors: Hall D. L. , Humble J. E. , Duldig M. L.
Published: July 2016

We have deduced the yearly averaged value of the solar diurnal variation as observed by a surface muon telescope and three underground muon telescopes over the years 1957 to 1985. This has allowed us to examine the temporal variation in both the latitudinal gradient Gz and the product of the parallel mean free path and the radial gradient of galactic cosmic rays during three consecutive solar cycles. The median rigidities of the primary particles being detected by the telescopes are 50 GV in the case of the surface muon telescope and greater than 150 GV in the case of the underground muon telescopes. We have compared our results with those of a similar study made from observations of the solar diurnal variation by neutron monitors and an ion chamber, which have median rigidities of response between 17 and 70 GV (Bieber and Chen 1991a). The product has a solar magnetic cycle dependence and our values are lower than those observed by neutron monitors, in agreement with the Bieber and Chen observation that reverses after a solar magnetic field reversal, in accordance with drift theories.
Intelligent Fault Diagnosis at the Australia Telescope
Authors: Landau Robert
Published: July 2016

The Fault Diagnosis Expert System for the Australia Telescope analyses ~12000 items of monitor data every minute that report the health and stability of specific components and signal pathways in the array. These data are divided into signatures which are matched against signatures of known failure modes to diagnose problems with the array. Knowledge about many of the failures is acquired by generating them in earlier tests. The system keeps a six-hour history of the detailed behaviour of all monitor data as well as the visibilities. It archives the data in half-hour intervals, characterising the interval with a small set of robust statistical estimators. An interactive graphical user interface allows the simultaneous display of twenty-four histories of either the 6-hour data or one week of the characterised data, together with options for plotting one history against another and for calculating their robust regression.
A Complete Sample of Southern Radio Sources: Radio, Optical and X-ray Properties
Authors: Morganti R. , Tadhunter C. N. , Fosbury R. A. E. , Oosterloo T. , Danziger I. J. , Alighieri S. di Serego , Siebert J. , Brinkmann W.
Published: July 2016

Radio, optical and X-ray observations of a complete flux-limited sample of southern bright radio sources have been analysed to investigate beaming and orientation effects in the different wavebands. We conclude that, in addition to beamed optical and radio components, there is evidence for anisotropic X-ray emission.
Possible Connection between Large-scale Structures
Authors: Di Nella H. , Paturel G.
Published: July 2016

From the Lyon-Meudon Extragalactic Database (LEDA) we constructed a sample of 27000 galaxies with radial velocities smaller than 15 000 kms−1. From this first sample we selected the 5683 largest galaxies, which constitute a sample complete up to the diameter limit D25 = 1·6′. This sub-sample has been used to search for the most populated plane. The result is that the plane defined by the pole (l = 52°; b= 16°) contains twice as many galaxies as would be found for randomly distributed galaxies. This plane is not far from the supergalactic plane. The distribution of galaxies in this plane has been studied by using the radial velocity as an estimate of the distance. An excess of galaxies appears at a distance of about 70 Mpc. We discuss the reality of this density enhancement which could result from selection effects.
Variability of Methanol Masers
Authors: Caswell J. L. , Vaile R. A. , Ellingsen S.P.
Published: July 2016

Sites of recent star formation often radiate strong maser emission from methanol transitions near 6-6 and 12 GHz. We have studied many of these masers over several years and find that intensity variations are common on both transitions. We present observations which demonstrate marked variability in 48 sources. We explore the characteristics of the variability and find it to be typically quasi-periodic, on a timescale of between a month and several years. The amplitude of the variation is most commonly less than a factor of two, but can reach factors of ten. The variability of different features in a source is usually independent. Variability of features seen at both 6·6 and 12 GHz is sometimes correlated, with larger amplitudes usually seen at 12 GHz. A likely inference is that variations are occasionally due to a change in the pump rate throughout the masing region, but most are consistent with a change in the masing path length due to large-scale motions. In addition, it is likely that the majority of 6·6-GHz masers are saturated whereas the 12-GHz masers may be somewhat less saturated.
Do We Expect to See Young Pulsars outside Their Parent Shells?
Authors: Gaensler B. M. , Johnston Simon
Published: July 2016

A recent study has indicated that a substantial fraction of young pulsars born in supernovae have travelled outside the boundaries of their corresponding shell supernova remnants. A simple model suggests that this should not be the case, implying either that some postulated pulsar/remnant associations are false, or that pulsars are particularly difficult to detect until they have emerged from their remnants.
Seeing Measurements at Freeling Heights and Siding Spring Observatory
Authors: Wood P. R. , Rodgers A. W. , Russell K. S.
Published: July 2016

A low-cost differential image motion monitor (DIMM), consisting of an 11-inch Celestron, an SBIG ST-4 autoguiding CCD camera and a PC, is described. Two such systems were used during June–July and November–December 1993 to make near-simultaneous seeing measurements at Freeling Heights in the Northern Flinders Ranges and at Siding Spring Observatory. The results of these campaigns show that the seeing-distribution is generally similar at both sites, with the most common seeing value being ~l·2″. Siding Spring does, however, have slightly more bad seeing (>2″) than Freeling Heights. Weather records from Arkaroola Resort (15 km south of Freeling Heights) indicate that there is ~15% less cloud cover at Freeling Heights than at Siding Spring. Episodes of rapid seeing deterioration at Siding Spring in winter are shown to coincide with warm air masses crossing the mountain.
Connecting a Star’s Convection Zone with its Corona
Authors: Galloway D. J. , Jones C. A.
Published: July 2016

This paper discusses problems which have as their uniting theme the need to understand the coupling between a stellar convection zone and a magnetically dominated corona above it. Interest is concentrated on how the convection drives the atmosphere above, loading it with the currents that give rise to flares and other forms of coronal activity. The role of boundary conditions appears to be crucial, suggesting that a global understanding of the magnetic field system is necessary to explain what is observed in the corona. Calculations are presented which suggest that currents flowing up a flux rope return not in the immediate vicinity of the rope but rather in an alternative flux concentration located some distance away.
Preliminary Results of a Survey of Ultracompact H II Regions
Authors: Walsh A. J. , Hyland A. R. , Robinson G. , Bourke T. L. , James S. D.
Published: July 2016

Ultracompact H II regions are small, dense regions of ionised gas surrounding high-mass stars which are still embedded in their natal molecular clouds. A survey of such regions has been commenced in an attempt to improve our understanding of the processes of high-mass star formation. The initial stages of the survey have involved selection of likely candidates from the IRAS Point Source Catalogue, correlation with radio continuum emission at 4·85 GHz and subsequent observations of methanol maser emission at 6·668 GHz. Preliminary results of the methanol maser survey are given.
Prospects for Coordinated Observations with XTE
Authors: Giles A. B. , Jahoda K. , Swank J. H. , Zhang W.
Published: July 2016

The X-ray Timing Explorer (XTE) is a NASA satellite designed to perform high-time-resolution studies of known X-ray sources. The two main experiments are a large-area proportional counter array (PCA) from the Goddard Space Flight Center (GSFC) and a high-energy X-ray timing experiment (HEXTE) from the University of California at San Diego (UCSD). The PCA data is processed by an electronic data system (EDS) built by the Massachusetts Institute of Technology (MIT) that performs many parallel processing analysis functions for on-board evaluation and data compression. MIT also provide an all-sky monitor (ASM) experiment so that XTE can be slewed rapidly to new transient sources. The spacecraft provides a mean science telemetry rate for the PCA of ~20 kilobits per second (kbps), with bursts to 256 kbps for durations of 30 minutes. Photons are tagged to 1 μs and absolute timing should be better than 100 μs. XTE is due for launch in late August 1995 and the first NASA Research Announcement (NRA) is due out in January 1995. This paper summarises XTE’s performance and then discusses the interactive and flexible operations of the satellite and some of the science it can do. These features should make XTE a productive spacecraft for coordinated observation programs.
Xvoigt: An Interactive Absorption Line Fitting Program for the X Window System
Authors: Max David P. , Bailey Geoff
Published: July 2016

We have developed an easy-to-use, mouse-driven program for the interactive fitting of interstellar absorption lines in high-resolution astronomical spectra. The program, Xvoigt, gives values for the column density and velocity dispersion of the absorbing clouds. It runs under the popular X Window system available on most workstations, and offers significant enhancements over existing profile-fitting software. Xvoigt can be an important adjunct to automatic programs for fitting absorption lines in low to moderate signal-to-noise QSO or other spectra, and is ideal for demonstrating the details and difficulties of absorption line analysis.
Remote Control of Astronomical Instruments via the Internet
Authors: Ashley Michael C.B. , Brooks Paul W. , Lloyd James P.
Published: July 2016

A software package called ERIC is described that provides a framework for allowing scientific instruments to be remotely controlled via the Internet. The package has been used to control four diverse astronomical instruments, and is now being made freely available to the community. For a description of ERIC’s capabilities, and how to obtain a copy, see the conclusion to this paper.
Installation of the J. L. Sersic Astronomical Observatory at 78° South
Authors: Recabarren Pablo , Mosconi Mirta , Lambas Diego García , Dellizzotti Juan , Ozu Sheiko , Hutka Julio
Published: July 2016

In 1994 December we installed a Celestron CG11 Telescope at Belgrano Base (previously called Belgrano II) for site seeing measurements and variable star observations. We describe the project, logistics, installation and working environment. We present the first quantitative observations of astronomical seeing conditions at Belgrano Base.
Magnetic Braking and Its Implication for CV Evolution
Authors: Wickramasinghe Dayal T. , Li Jianke , Wu Kinwah
Published: July 2016

We review the models of magnetic braking for synchronously rotating magnetic cataclysmic variables, and discuss the implications of magnetic braking for orbital evolution and the upper limit to the magnetic fields (about 70 MG) of the observed AM Herculis systems.
Some Intrinsic Properties of Parsec-scale Radio Jets
Authors: Tingay Steven J.
Published: July 2016

A simple model for estimating the intrinsic flow direction and speed in the parsec-scale jets associated with extragalactic radio sources is presented. In this model, radio source brightness asymmetries are attributed to the apparent amplification caused when a relativistic jet of radiating material is somewhat aligned with the observers line of sight. The knots of emission commonly seen in parsec-scale radio jets are interpreted as shocks in the relativistic fluid.
The Large-scale Distribution of Radio Sources
Authors: Drinkwater Michael J. , Schmidt Robert W.
Published: July 2016

We have used a sample of 263 Parkes half-Jansky flat-spectrum radio sources to measure the spatial correlation function of radio galaxies and radio-loud quasars on scales up to 1000 h−1 Mpc. We do not detect any clustering in the sample. If any undetected clustering is described by a power-law spatial correlation function [ξ(r) = (r/r0)−1·8], we can rule out clustering with scales r0 ≥ 50 h−1 Mpc at the 99·9% confidence level. We have also used the sample to test for the ‘possible’ large concentration of quasars in the direction of the microwave background dipole found by Shaver (1987). There is no evidence for such a concentration in our data and we show that the earlier result was probably biased by the use of non-uniform image classifications.