bluuebunny/crossref_metadata_2025 huggingface dataset:
The North–South Anisotropy and the Radial Density Gradient of Galactic Cosmic Rays at 1 AU
Authors: Hall D. L. , Duldig M. L. , Humble J. E.
Published: July 2016

The radial density gradient (Gr) of Galactic cosmic rays in the ecliptic plane points outward from the Sun. This indicates an increasing density of cosmic ray particles beyond the Earth’s orbit. Due to this gradient and the direction of the Sun’s interplanetary magnetic field (IMF) above and below the IMF wavy neutral sheet, there exists an anisotropic flow of cosmic ray particles approximately perpendicular to the ecliptic plane (i.e. in the direction parallel to BIMF × Gr). This effect is called the north–south anisotropy (ξNS) and manifests as a diurnal variation in sidereal time in the particle intensity recorded by a cosmic ray detector. By analysing the yearly averaged sidereal diurnal variation recorded by five neutron monitors and six muon telescopes from 1957 to 1990, we have deduced probable values of the average rigidity spectrum and magnitude of ξNS. Furthermore, we have used determined yearly amplitudes of ξNS to infer the magnitude of Gr for particles with rigidities in excess of 10 GV.
MHD Turbulence in an Accretion Disk
Authors: Hawley John F. , Balbus Steven A.
Published: July 2016

A long-standing problem in the theory of astrophysical accretion disks has been to determine the nature of the stress that transports orbital angular momentum outward. The discovery of a local MHD instability is strong evidence that transport occurs through turbulent Maxwell and Reynolds stresses. Using numerical simulations, we have demonstrated that a weak seed magnetic field in an accretion disk shear flow is unstable and leads to sustained MHD turbulence at dynamically important levels.
Quiescent Non-thermal Radio Emission from Stellar Systems
Authors: Storey Michelle C. , Hewitt R. G.
Published: July 2016

Non-thermal radio emission has been detected from dMe stars, RS CVn binaries and W T Tauri stars. Polarisation and intensity measurements of the quiescent (i.e. non-flaring) emission indicate that the emission is gyrosynchrotron emission from mildly relativistic electrons spiralling in a magnetic field. A three-dimensional dipole magnetic field model for the stellar field is presented and the quiescent gyrosynchrotron emission from such a model is calculated and compared with observations. The model can account for many phenomenological features of quiescent emission. Quantitative comparisons of model results with observations indicate that the electron distribution in the emission region may be a magnetic mirroring distribution.
Infrared Surveys from Antarctica
Authors: Bailey Jeremy
Published: July 2016

The very low background observed from Antarctica in a window from about 2·25 to 2·45 μm can be exploited as a way of making deep near-IR surveys over wide areas of sky. Imaging surveys using the entire window can cover large areas of sky to limits of around K = 20, and can be used to study galaxy evolution and to search for high-redshift quasars, dust-obscured quasars and brown dwarfs. It is also possible to make spectroscopic surveys in this window. The window includes molecular hydrogen emission and CO absorption in galactic sources, and can also be used to search for emission lines such as Hα in high-redshift star-forming galaxies.
The Antarctic Submillimeter Telescope and Remote Observatory (AST/RO)
Authors: Balm Simon P.
Published: July 2016

The Antarctic Submillimeter Telescope and Remote Observatory (AST/RO) is a highly automated 1·7 m diameter telescope aimed at exploiting the superb submillimetre skies of the Antarctic Plateau for astronomy and aeronomy studies. It was recently installed at the Amundsen-Scott South Pole Station during the 1994/95 Austral season and is currently undergoing its first winter-over of operation. In this paper we briefly outline the capabilities of the instrument and describe some recent achievements culminating in the telescope’s first observations of the South Polar submillimetre sky.
An Instrument Devoted to the Study of mm/sub-mm Galactic Emission at Dome C
Authors: Dall’Oglio G. , Miriametro A. , Morgante G. , Pizzo L. , Valenziano L.
Published: July 2016

An experiment has been developed in order to map the submillimetre Galactic emission at four different wavelengths between 400 μm and 2 mm at an angular scale of 1°. A binocular telescope system has been realised by means of two off-axis wobbling parabolic mirrors, each one coupled to a two-channel 3He photometer. A first run of observations from Dome C is planned for the Antarctic summer 1995–96.
The Influence of Magnetic Fields on Star Formation
Authors: Byleveld S. E. , Pongracic H.
Published: July 2016

Numerical simulations suggest that colliding molecular clouds induce gravitational collapse and may be responsible for star formation. We incorporate magnetic fields in these simulations and present preliminary results of an investigation of the influence of magnetic fields on star formation via this process.
Preliminary Radio Continuum Maps of Three Spiral Galaxies
Authors: Mazzolini Margaret , Webster Rachel
Published: July 2016

The Australia Telescope Compact Array has been used in two 6 km configurations to make 12 hour observations of the radio continuum structure of three spiral galaxies at 1380 MHz and 2378 MHz. Radio maps of NGC 1792, 6300 and 1097 are presented here, as part of a survey to find examples of anomalous radio structures in spiral galaxies.
Shock Acceleration in Hot Spots
Authors: Pope M. H. , Ball Lewis , Melrose D. B.
Published: July 2016

A simple model is presented for electron acceleration in extragalactic radio sources with two hot spots. The effect of diffusive shock acceleration by multiple shocks is calculated numerically, with adiabatic and synchrotron losses included. It is found for the sources 3C 20 and 3C 268·4 that a consistent set of model parameters exists which reproduce the observations. The model fails to reproduce the observations for the source 3C 196.
Research Programs at the Carter Observatory: An Overview
Authors: Dodd R. J. , Orchiston W.
Published: July 2016

An outline is given of the main research programs currently in progress at the Carter Observatory. These include: the establishment of a set of standard star magnitudes and colours in the Vilnius seven-colour photometric system; the study of galactic and extragalactic star clusters using Vilnius and broadband photometries; binary stars and the development of APTs; and the history of Australasian astronomy. The role of Carter Observatory Honorary Research Associates is described and mention is made of the joint New Zealand/Japan program to observe gravitational microlensing effects, discover variable stars and patrol selected clusters of galaxies for supernovae.
The Magellanic Clouds at Millimetre Wavelengths: A Brief Overview
Authors: Staveley-Smith Lister
Published: July 2016

There are several excellent reasons for studying the Magellanic Clouds at millimetre wavelengths with a telescope such as the AT Mopra antenna:

• The Magellanic Clouds are the nearest young, gas-rich galaxies to the Galaxy. They are therefore ideal places to study the processes which lead to star formation, and for comparing these processes with Galactic processes.

• The distances of the Clouds are well established at close to 50 kpc for the LMC and 60 kpc for the SMC.

• The Mopra beam at 2·6 mm (CO) corresponds to ~10 pc, which is comparable with the size of molecular clouds and complexes in the LMC and SMC (e.g. Rubio et al. 1993). The Mopra beam is also complementary to that obtainable at low frequencies with the AT Compact Array for continuum and HI studies (e.g. the 750 m configuration at 21 cm will give a resolution of ~12pc).
Neural Networks and the Classification of Active Galactic Nucleus Spectra
Authors: Rawson Daya M. , Bailey Jeremy , Francis Paul J.
Published: July 2016

The use of artificial neural networks (ANNs) as a classifier of digital spectra is investigated. Using both simulated and real data, it is shown that neural networks can be trained to discriminate between the spectra of different classes of active galactic nucleus (AGN) with realistic sample sizes and signal-to-noise ratios. By working in the Fourier domain, neural nets can classify objects without knowledge of their redshifts.
The Signal Method
Authors: Whitehurst Robert
Published: July 2016

This paper presents a new Lagrangian approach to the numeric solution of the equation of gas dynamics in two dimensions. This, the signal method, is implemented here as a free Lagrange method in the code FLAME. The signal method is conservative, stable, unsplit, positive definite, accurately tracks strong shock fronts with ease, and adapts to and follows complex gas flows for long times. No artificial viscosities are introduced. No special knowledge of the solution is required in advance and only local information is used.
Shocks in Molecular Clouds
Authors: Brand Peter W. J. L.
Published: July 2016

A one-day workshop discussed the properties of shocks in star-forming regions. It also reviewed other physical processes in star-forming molecular gas, and the progress in numerical modelling of such physics. Discussion concentrated on the complexity which instabilities in the gas flow bring to the analysis of shocks. The consensus was that progress will be made as the spatial/spectral resolution of shock measurements improves, and as numerical modelling of the nonlinear growth of instabilities becomes possible, potentially leading to statistical models of shock dynamics.
Spectra, Dimensions and Luminosities of Radio Sources in the Culgoora-3 List
Authors: Slee O.B. , Siegman Betty C. , Mulhall P.S.
Published: July 2016

The Culgoora-3 list of radio sources (Slee 1977) contains measurements at 160 MHz of about 2000 sources which had earlier been examined at 80 MHz (Slee and Higgins 1973, 1975). The observations were made with the Culgoora radioheliograph, a 3-km-diameter ring of 96 reflectors, which achieves angular resolutions (full half-power width) of 3′.7 and 1′.9 arc at 80 and 160 MHz respectively; it has an effective collecting area of ~6000 m2.
HI in the Small Magellanic Cloud Re-examined — II
Authors: McGee R.X. , Newton Lynette M.
Published: July 2016

The reasons for re-surveying the neutral hydrogen in the Small Magellanic Cloud and the results from that survey are briefly discussed in our previous paper (McGee and Newton 1982 — Paper I). We now present the experimental details, the 489 observed line profiles and details of the Gaussian analysis of each one. The profiles here are from the ‘main body’ of the SMC. Those of the ‘bridge region’ between the two Clouds of Magellan will form the basis of a later paper.
Magnetic White Dwarfs in Binary Systems
Authors: Wickramasinghe D.T.
Published: July 2016

The cataclysmic variables are close binary systems consisting of a late type star and a collapsed star, usually a white dwarf, undergoing mass exchange. According to the standard model, the late type star (the secondary) fills its Roche lobe and material escaping from the inner Lagrangian point is transferred to the primary by means of a mass transfer stream and an accretion disc. The spectroscopic and photometric properties of most cataclysmic variables can be understood in terms of radiation from the various components of such a system, with the accretion disc usually dominating in the optical region (see Warner (1976) for a review). However, recently a new class of cataclysmic variables has been discovered with distinctive optical properties that are inexplicable in terms of the standard model. These systems known as the AM Herculis type variables have provided the first direct evidence for the presence of strong magnetic fields in the white dwarfs of some cataclysmic variables. We present here a review of some of the important properties of these variables with emphasis on the unique system VV Puppis which has provided the first unequivocal evidence for high harmonic cyclotron radiation from white dwarfs.
The Kinematics of Cyclotron Emission for Quantized Electrons
Authors: Melrose D.B. , Hewitt R.G. , Parle A.J.
Published: July 2016

Since the work of Wu and Lee (1979) there has been renewed interest in the classical theory of electron cyclotron masers (Lee and Wu 1980, Lee et al. 1980, Wu et al. 1981, 1982, Hewitt et al. 1981, 1982, Melrose et al. 1982, Omidi and Gurnett 1982, Melrose and Dulk 1982). A useful idea in these recent developments of the classical theory concerns a geometric interpretation of the classical gyroresonance condition

where Ωe, is the nonrelativistic gyrofrequency, s = 0, ± 1, ± 2,… is the harmonic number, is the Lorentz factor and ║ and ┴ denote components parallel and perpendicular to the magnetic field. In v┴ − v║ space (1) represents an ellipse with centre v║ = vc, v┴ = 0, eccentricity e0 and semi-major axis V parallel to the v┴ axis, with
Plasma Distribution Functions in Accretion onto Neutron Stars
Authors: Cramer N.F.
Published: July 2016

In the usual model of discrete cosmic X-ray sources, it is assumed that a massive star loses matter to a companion neutron star, either through a stellar wind, or by means of Roche lobe overflow into an accretion disk around the neutron star (Pines 1980). The irifalling matter becomes ionized and is channelled along the magnetic field lines of the neutron star, so that it is accreted onto the star in a very small region at the magnetic polar caps. The physical conditions at these points are assumed to be: magnetic field B ~ 1012 G, plasma temperature ~107-108 K, and infall plasma velocity ~ 0.3 c-0.5 c.
A Sequence of E-Type Composite Analytical Solutions of the Lane-Emden Equation
Authors: Murphy J.O.
Published: July 2016

The polytropic stellar model with index n = 0 has a uniform density distribution throughout, and consequently its physical radius is essentially arbitrary because the surface density condition, ϱ = 0, is never satisfied. This surface anomaly, which is not associated with the other polytopic models for 0 < n ≤ 5, could be a constraining factor in certain astrophysical applications involving the n = 0 polytrope. For example, in some circumstances it may be appropriate to utilize the simple physical formulation of the model but on the other hand inappropriate to disregard any zero boundary requirements for the surface density. A sequence of new E-type (as defined below) composite analytical solutions to the Lane-Emden equation, based on the indices 0 and 1, has been developed which eliminates this physical indetermination. The associated polytropic models can be classified as essentially uniform density models. Specifically, they have a large central uniform density n = 0 zone matched, in a physically consistent way, to a small outer n = 1 zone which has a steep density gradient giving ϱ = 0, along with T = 0 and P = 0, at the radial distance corresponding to the first zero of the composite solution.
Artificial Viscosity and the Simulation of Fragmentation
Authors: Gingold R.A. , Monaghan J.J.
Published: July 2016

Recent numerical experiments (Norman et al. 1980), which simulate the axisymmetric collapse of a rotating, self gravitating cloud, show that spurious angular momentum transport can seriously affect the evolution of the cloud. In particular, it may determine if a ring-like density enhancement will occur. The spurious angular momentum transport can arise either from an explicit artificial viscosity, which might be required if shocks occur, or from an implicit viscosity due to truncation errors in the difference equation approximation to the exact equations. In donor cell schemes like those used by Tohline (1980) and Boss (1980) spurious angular momentum transport is due to truncation errors in the difference equations. For axisymmetric problems the errors are usually not serious since the typical length of a cell in the computational grid is very much less than the length scale of the cloud. We would expect the errors to be much greater when fragmentation occurs because the length scale of a fragment may only be comparable to that of three or four cells.
Period Variations of the Eclipsing System DI Pegasi
Authors: Kennedy Harold D.
Published: July 2016

DI Peg has been recognised as an eclipsing system since 1934 when Morgenroth (1934) discovered its variability. For over fifty years, many observers [Jensch (1934), Opalski (1936), Tsesevich (1954), Szafraniec (1956), Kruszewski (1956), Huth (1966), Rucinski (1967), Binnendijk (1973)], have studied this system. DI Peg was observed at Midway Observatory (M.O.) during 1976 and 1977 (Kennedy 1978). Considering the erratic period changes of the system, it appeared desirable to check the system again during 1980.
The Brightness Variations of Asteroid 216 Kleopatra
Authors: Kennedy H.D. , Tholen D.J.
Published: July 2016

Since the discovery of the first asteroid by Piazzi in 1801, orbits have been determined for over 2500 with varying degrees of quality; 2357 have been assigned permanent numbers as of this writing (Marsden and Bardwell 1981).
Observations of the 1→0 Transition of CO Towards Southern HII Regions
Authors: Whiteoak J. B. , Otrupcek Robina E. , Rennie C. J.
Published: July 2016

The 4-m radio telescope of the CSIRO Division of Radiophysics at Epping is being used to survey the line emission associated with the 1→0 transition of CO (rest frequency 115.271 GHz) in the southern Milky Way. The programme includes mapping the CO distribution across giant molecular-cloud/HII-region complexes. As a first stage the emission has been observed towards bright southern HII regions. These results will not only serve as a basis for future extensive mapping but will also provide data which is directly comparable with observations of other molecular lines that have been made towards the HII regions.
L1642 — A Dust Cloud in a Cometary Globule?
Authors: Taylor M. I. , Taylor K. N. R. , Vaile R. A.
Published: July 2016

Lynds 1642 is a small, somewhat insignificant dark cloud centred at 04h33, — 14°20 (1950). On a IIIaJ UKSTU Schmidt plate it may be seen to lie within an approximately circular patch of nebulosity which we believe to be visible by reflection. Its galactic location (l = 210°.9 b = -36°.5) places it beneath the local arm in the direction of Orion and it is likely that it is seen by reflection of the integrated light of the stars in that region of the galaxy.
The Potential for Far-infrared Astronomy in Australia
Authors: Storey J. W. V.
Published: July 2016

Despite its superb optical and radio observatories, Australia is essentially blind to the entire submillimeter and far-infrared spectrum. The importance of this spectral region can perhaps best be illustrated by reference to Figure 1, which shows the flux of the galaxy NGC253 as a function of frequency.
The Astronomical Objectives of the 6m Radiotelescope of the University of NSW
Authors: Fourikis N.
Published: July 2016

Observations of non-variable sources of astronomical interest can be ideally undertaken at national radio astronomy observatories whenever possible. By contrast observations of variable sources at sporadic intervals of time, taken at the same observatories, can provide the interest/impetus to observe these sources as often as possible. Since national observatories are overloaded with requests for observations of diverse nature, observations of variable sources cannot be undertaken at these observatories on a daily basis. In consequence dedicated telescopes are required for the continuous monitoring of variable sources.
The ‘High Velocity Cloud’ Origin of the Magellanic System
Authors: Mathewson D. S. , Wayte S. R. , Ford V. L. , Ruan K.
Published: July 2016

It is believed that the splitting of the SMC into two fragments and the production of the Inter-Cloud gas and the Magellanic Stream occurred in the one event 4 × 108 years ago. This event was a collision between the LMC and SMC. This time is too short for the Stream to be tidal, or be the result of stripping of the Inter-Cloud gas by a diffuse gaseous halo. It is proposed that the clouds in the Stream are the results of collisions between the Inter-Cloud gas and HVCs in the Galactic halo. A model of this process accounts for all of the observational features of the Stream. Observations of HVCs in the path of the Magellanic Clouds are used to predict the development of the Stream. The HVCs in our halo are thought to be a result of a collision of a galaxy with our Galaxy 6 × 109 years ago.
Colour changes in mid-B star variables
Authors: Watson R. D.
Published: July 2016

Model predictions of light changes due to non-radial stellar pulsation have been compared with the observations of light and colour changes in mid-B star variables made by Waelkens and Rufener (1985). It is concluded that these observations are consistent with the presence of low l (dipole and quadrupole) non-radial pulsations in the stars. This strengthens Waelkens and Rufener’s hypothesis that these variables may be identified with the 53 Persei stars. The differences between the model predictions for these large Q variables, which have periods in the 1 to 3 day range, and the predictions of small Q models, which apply to β Cephei variables, are explained.
Observations of Active Stars at 843 MHz
Authors: Vaughan A. E. , Large M. I.
Published: July 2016

The Molonglo Observatory Synthesis Telescope is being used in a continuing program of observation of known Southern active stars. By May, 1987, a total of forty-one stars had been observed and 843 MHz quiescent emission, presumably associated with the star, had been detected in nine instances. The emission from five of these stars has shown marked variation on a time-scale > 1 day.
Strömgren photometry of supergiants in the Magellanic Clouds
Authors: Russell S. C. , Bessell M. S. , Dopita M. A.
Published: July 2016

This is a preliminary report on the first Strömgren–Hβ photometric survey of yellow supergiants in the Magellanic Clouds. Less luminous supergiants have been chosen in preference for this program in order to facilitate calculation of their physical parameters. This will not only provide a basis for future detailed spectral analysis of these stars, but will allow a better calibration of the colours derived from model atmospheres for this type of star. The colours of these stars are more affected by changes in metallicity than the hotter stars more frequently studied, and since they are also young, they reflect the metallicity of their local InterStellar Medium (ISM). If indeed the Strömgren abundance index m1 can be calibrated successfully for these stars, then their observation in any galaxy will provide the metallicity of that particular ISM. Our results show that it is important for future colours to be calculated over the range of turbulent velocities important for supergiants.
SN 1987a: A Progress Report
Authors: Dopita M. A. , Achilleos N. , Dawe J. A. , Flynn C. , Meatheringham S. J. , McNaught R. D.
Published: July 2016

It now appears almost certain that the precursor of SN 1987a was the brighter of the components of Sk-69 202, a blue supergiant, with a precursor mass of perhaps 12-16 solar masses. Prior to the explosion the precursor had a core mass of order six solar masses, and 0.1 to 0.2 solar masses of residual hydrogen envelope. The compact nature of this star can account for many of the odd features of the subsequent light curve and spectral evolution.

An analysis of the light curve and colour evolution shows four distinct epochs, which probably relate to the initial expansion of the fireball and the escape of shock-deposited thermal energy, the hydrogen-rich layers becoming optically thin, the exposure of the helium core, and the increasing transparency of the helium core.

The supernova appeared to be at its maximum on May 10, but is dimmer than a normal Type II because its light is apparently derived from recombinations and the radioactive decay of 56Ni to 56Co to 56Fe rather than by the thermal energy deposited by the passage of the shock.
The Australian Radio Star Survey
Authors: Wright Alan E. , Slee O. B. , Nelson G. J. , Stewart R. T. , Jauncey David L. , White Graeme L. , Vaughan A. E. , Lim J. , Large M. I. , Bunton John D. , Thompson K. , Coates D. W. , Innis J. L. , Peters W. L. , Ryan S. G. , Robinson R. D. , Cropper Mark , Allen David A. , Page A. A.
Published: July 2016

We present an overview of the survey for radio emission from active stars that has been in progress for the last six years using the observatories at Fleurs, Molonglo, Parkes and Tidbinbilla. The role of complementary optical observations at the Anglo-Australian Observatory, Mount Burnett, Mount Stromlo and Siding Spring Observatories and Mount Tamborine are also outlined. We describe the different types of star that have been included in our survey and discuss some of the problems in making the radio observations.
Periodic Analysis of Gamma-Ray Data
Authors: Protheroe R. J.
Published: July 2016

In γ-ray astronomy one often wishes to search for a periodic signal from a suspected point source. Either one knows the period in advance, for example in the case of a radio pulsar, or at least a range of possible periods, or one has no information and is searching “blind”, as in the case of SN1987a, unidentified sources in the COS-B catalogue, or binary X-ray sources without known pulse periods. In both cases one should adopt a strategy which give the best chance of obtaining a statistically significant result. The power of tests using the family of statistics based on the Rayleigh statistic is discussed for two extreme forms of possible light curves: a uniform distribution plus a delta function, and a cartoid distribution. Strategies for using these statistics are discussed. Methods of obtaining confidence bands, and in the case of an unsuccessful search, upper-limits to any pulsed component are described, and graphs given which enable these to be calculated readily given the value of the statistic obtained.
115 GHz CO Distribution towards the Southern Coalsack
Authors: Otrupcek Robina E. , Wang Jing-sheng
Published: July 2016

Observations have been made, using the Epping 4-m radio telescope, of emission from the J = 1-0 transition of CO (115 GHz) towards the Southern Coalsack. The half-power beam-width was 2′.7 arc and the radial velocity resolution was 0.07 km s−1. The line was found to be distributed with varying intensity over an area of 63′ × 36′ arc. The mean radial velocity was −5.8 km s−1 and mean half-intensity linewidth 1.18 km s-1. A typical line temperature was 8 K with maxima exceeding 12 K. The results suggest a stable dark cloud region with no significant evidence of systematic motions.
Upper Limits to the Prompt X-ray Flux from Supernova 1987a
Authors: Edwards P. J.
Published: July 2016

The literature contains numerous predictions of an X-ray pulse associated with the emergence of the shock-wave at the surface of a star undergoing a supernova explosion. Applied to supernova 1987a, these suggest a small, solar-flare like event lasting about a minute with a terrestrial flux of order 1 μWm-2 and a black-body temperature between 106K and 107K occurring between 0900 and 1000 UT on February 23, 1987. Unfortunately, no direct X-ray observations appear to have been made. However, such an event would be expected to give rise to an observable enhancement of ionization in the upper D-region of the ionosphere. The absence of a detectable perturbation in VLF radio signals propagating in the earth-ionosphere waveguide sets upper limits to the X-ray flux and temperature below those predicted.
Cometary Dust and the Rainfall Singularity Shift
Authors: Kviz Z.
Published: July 2016

Daily rainfall data for Sydney, Prague and Moscow for singularities around 26 May and 9 November were examined by an autocorrelation method. Intervals between 2 and 7 days were used for the autocorrelation. In all three samples the wider the interval used the later the date of the best autocorrelation. The shift is discussed from the point of view of the Bowen hypothesis on meteor-rainfall correlation. Also new results supporting the Bowen hypothesis and its new version on bacteria from space, published recently, are briefly discussed.
The Discovery
Authors: McNaught R.D.
Published: July 2016

The story of the discovery of SN 1987A by Ian Shelton and Oscar Duhalde is well known, but many other events around the time of discovery are largely unknown. I shall describe these events and some of the confusion generated on 24 February 1987.
Spectropolarimetry of SN 1987A with the AAT
Authors: Bailey Jeremy
Published: July 2016

Spectropolarimetric observations of SN 1987A obtained with the AAT are presented and discussed. The foreground interstellar polarization is estimated to have a value of 0.8% at position angle 40°. In the early stages polarization features on the absorption troughs of the P-Cygni profiles are observed. At later stages the polarization is dominated by the effects of electron scattering. After correction for the effects of interstellar polarization the position angle of the electron scattering polarization is 110°. The spectrum of the polarized radiation shows broad redshifted features corresponding to the emission lines which can be understood as the consequence of electron scattering in an expanding atmosphere. The position angle observed is consistent with the elongation of the supernova image seen by speckle inteferometry.
The Evolution of a Horizontal Scale for Oscillatory Magnetoconvection
Authors: Murphy J.O. , Lopez J.M.
Published: July 2016

Oscillatory convective motions have been observed in the umbrae of sunspots and, in the past, the linear theory of overstability has been used for sunspot models. Here a non-linear model for oscillatory convection has been used to investigate the possibility of a preferred horizontal cell size for these motions, in the presence of a magnetic field.

The integration forward in time, from the conductive state, of the non-linear multimode equations governing magnetoconvection when the magnetic Prandtl number is less than one portrays a complex interaction between the evolving magnetic and vertical velocity horizontal scales. Preferred horizontal scales for the convective cells have been established by identifying the modes that substantially contribute to the overall convective heat transport. All other modes, although initially perturbed, in time essentially decay to zero through self interaction.
Radio and Optical Observation of an Intense Flare on HD 32918
Authors: Bunton John D. , Large M. I. , Slee O. B. , Stewart R. T. , Robinson R. D. , Thatcher John D.
Published: July 2016

During routine monitoring of active-chromosphere stars in August 1987 an intense radio flare on the FK Comae star HD 32918 was detected by the Parkes radiotelescope. Other observatories were notified, enabling data to be collected at 843 MHz, 1.4 GHz, 8.4 GHz and optical frequencies.

The flare at radio frequencies was largely similar to a previous event on this star, reaching a peak radio power of 5 < 1012 W Hz−1 at 8.4 GHz. During the flare the spectrum varied as ∼ v1.4 and later flattened as the flare progressed. Compared to the previous flare, circular polarization was higher.

Ca II and Hα optical spectra taken at the AAO 3.9-metre telescope show the star to have a highly active chromosphere and a strong wind, with a terminal velocity of ≈230 km s−1. While much of this activity appears to be long lived, there is good evidence for an increase in the strength of the chromospheric lines during the radio flare event.
The Solar Cycle: A Central-Source Wave Theory
Authors: Bracewell R. N.
Published: July 2016

Studies stimulated by the interpretation of the Elatina formation in South Australia as a fossil record of solar activity have led to discoveries of previously unnoticed features of the sunspot cycle record and to a theory of origin of the sunspot cycle that postulates a solar core in torsional motion and a magnetomechanical wave that couples to the photosphere. The considerations supporting the solar interpretation of the Elatina formation are gathered together.
Ultra High Energy Gamma Ray Astronomy at Akeno
Authors: Edwards P. G. , Kifune T. , Mori M.
Published: July 2016

This paper describes the SPICA array at Akeno, and discusses recent efforts made to improve the angular resolution of the array, concentrating on the determination of the departure of the shower front from a plane. Future research plans are also outlined.
The Fanaroff-Riley Classification of Southern Extragalactic Radio Sources
Authors: Jones P. A.
Published: July 2016

A sample of 339 extragalactic radio sources, noted as extended or multiple in the Molonglo Reference Catalogue, has been observed with the Molonglo Observatory Synthesis Telescope at 843 MHz. It is found that the strong sources all have edge-brightened morphology, while weak sources may be edge-brightened or edge-darkened. The morphological classification of Fanaroff and Riley is not a sharp division by luminosity. The degree of edge-darkening or edge-brightening is better parametrised by one-dimensional moments along the major axis than by the ratio of the separation between brightness maxima to the total extent as used by FR.
Flux Densities at 8400 MHz for a Large Sample of Parkes Radio Sources
Authors: Wright Alan E. , Wark Robin M. , Troup Euan , Otrupcek Robina , Hunt Andrew , Cooke David J.
Published: July 2016

We give a progress report on a programme of observations to obtain flux densities at 8.4 GHz for a large sample of radio sources selected from the Parkes 2700 MHz Survey. So far, about 1000 flux measurements have been made with a typical accuracy of 10%.
High Energy Transient Ionospheric Monitoring Network
Authors: Edwards Paul J.
Published: July 2016

Continuous, wide sky coverage is essential for the detection and monitoring of infrequent, short-lived events of astrophysical interest such as supernova and nova explosions, variable X-ray sources, gamma ray bursts, gravity waves and stellar and solar flares. We propose to (1) examine past radio propagation records and (2) develop new computer based radio receivers to monitor and log ionospheric perturbations associated with these events.
The Effect of Dust Shell Emission on the Strengths of Infrared Spectral Features in OH/IR Stars
Authors: Hyland A. R. , Robinson G.
Published: July 2016

We have constructed theoretical spherical dust shell models using a full radiative transfer treatment, to investigate the effect of thermal emission on the strengths of molecular CO and H2O features in late type stars with circumstellar dust shells and to establish the optical depth at which the strengths of the bands are significantly affected. In this study, for the first time the central sources have been represented by realistic atmospheric models for cool stars in the temperature range 2500–3000 K, which are representative of the central stars of OH/IR sources. Parameters of the dust shell models were chosen to fit the observed run of colours from 1.25–5 μm of a large sample of OH/IR sources using ‘dirty silicate opacities’. The results show that the molecular band strengths in the 2 μm region are significantly affected by the dust emission only when the optical depth in the shell reaches a value of τ1μm ≈2 for T* = 2500 K and somewhat less for T* = 3000 K. However, the changes are such that the distinction between supergiant-like spectra, and variable M-star spectra is retained in models with very high shell optical depths. The implications of these models are discussed in relation to previous observations of OH/IR sources.
The Energy Release in Solar Flares: Implications of a Constant-Current Model
Authors: Melrose D. B.
Published: July 2016

A model is explored for energy release in solar flares that involves a constant coronal current. An emerging flux tube is assumed to carry a current I≲1012 A, and this current is assumed not to change during flare. Using a circuit model, explosive energy release is attributed to a rapid rise in the coronal resistance Rc, which must adjust to Rc = − Lc, with Lc the rate of change of the coronal inductance Lc, to ensure I = constant. In this model the total energy released in the corona is twice the change in the magnetic energy stored in the corona. It is argued that this energy is inadequate to power a large flare and the implications of this conclusion are discussed.
Variation of the Current Profile in a Solar Flare
Authors: Khan J. I.
Published: July 2016

Variation of the electric current profile as a means of energy release in a solar flare is investigated. In particular, the change in magnetic energy is calculated for some simple idealized cases of the current profile. It is suggested that current profile changes may explain the smallest observed energy release structures in a flare.
A Catalogue of QSOs and Link Stars for the HST link of the Hipparcos Reference Frame
Authors: White Graeme L. , Jauncey David L. , Reynolds John E. , Malin David , Argue A. N. , Russell J. L. , Johnston K. J. , Hemenway P. D. , de Vegt Chr.
Published: July 2016

We present a list of bright (< 17 mag) southern QSOs and bright (< 11 mag) stars that may be suitable for theHubble Space Telescopelink between theHipparcosastrometric reference frame and the VLBI extragalactic frame. The QSOs have been selected from various lists of radio objects and identifications. The stars have been selected from the Strasbourg (CDS) data base and from the Preliminary Second Cape Photographic Catalogue, and supplemented with stars measured from the SERC IIIa-J Schmidt survey. The list of QSOs and stars have been included in theHipparcosandHSTschedule of observations.
Formation of Giant Molecular Clouds Associated with Spiral Structure
Authors: Song Guoxuan
Published: July 2016

Molecular hydrogen in spiral galaxies is distributed in clumps, i.e., molecular clouds, which have mass between 103M⊙ and 106M⊙ and a mass spectrum of n(m) ∝ m−1.6. Molecular clouds with masses greater than 105M⊙, are called giant molecular clouds (GMCs). It is generally accepted that GMCs are formed by the coalescence of molecular clouds through their collision. This process is studied by both numerical simulation and numerical integration. The observation with high resolution identified a great number of CO emission cores in galaxies. Based on this result, the aggregation or clustering formation of GMCs is numerically simulated. In the process of either coalescence or clustering, spiral perturbation plays an important role.
Flaws in the Modern Laplacian Theory of the Solar System
Authors: Monaghan J. J.
Published: July 2016

The Modern Laplacian Theory (Prentice 1978) of the origin of the solar system assumes a non-dissipative model of supersonic turbulence and the existence of stable rings left behind during the contraction of the proto-Sun. We show by numerical simulation that the turbulence is highly dissipative and the rings are unstable. As a result of the instability the rings spread and interact with the proto-Sun. The rings therefore cannot form in the way Prentice has proposed.
Spectral Observations of Nova Vulpeculae (1) 1984
Authors: McCain Claudia F. , Hidayat Bambang
Published: July 2016

We present the results of spectral observations on Nova Vulpeculae (1) 1984 (RA = 19h24m, Dec = 27° 15′), taken on 1984 August 21 (JD 2445934.4) and 1984 August 31 (JD 2445944.4). The data obtained gives additional information on the nova’s spectral evolution presented by Andrillat and Houziaux (1985), filling the gap in their observations.
Emission Line Variability of DR Tau
Authors: Isobe Syuzo , Norimoto Yuji , Kawakami Hajime
Published: July 2016

This paper presents results of CCD observations of DR Tau which show emission line variability.
Estimation of Mass-loss Rates for Some Galactic Wolf Rayet Stars
Authors: Woo Jong Ok
Published: July 2016

The absolute measurements of flux emitted in the visible continua of some Galactic Wolf-Rayet stars were carried out by means of a two-channel scanner. The measurements lead to the determination of stellar angular diameters which enable us to compute log L*/L⊙. The stellar wind terminal velocity, V∞ was obtained from the empirical relation of the effective temperatures by Underbill (1983) and V∞, adopted from the work of Willis (1982). Also, we derived the rate of mass loss for the WR stars from the formula Ṁ = є(Teff)L/(V∞c) by using the obtained effective temperatures, luminosity and V∞ in this work. The values of the rates range from 1.4 × 10−5 to 5.8 × 10−5M⊙yr−1.
12.2 GHz CH3OH Absorption in Southern Molecular Clouds
Authors: Peng R. , Whiteoak J. B.
Published: July 2016

We have used the Parkes 64m telescope to observe the 20 → 3−1E absorption of CH3 OH at 12.2 GHz towards 58 Galactic H II regions and dark clouds, yielding 38 detections. The results show that CH3 OH absorbing clouds have a typical optical depth of 0.25 and a column density of 8.4 × 1015 cm−2. CH3 OH absorption is often accompanied by unsaturated maser emission and is closely associated with background H II regions. CH3 OH absorption against the 2.7 K background is also observed in several dark clouds.
Differential Photometry of the Suspected Two-hour Variable UV-bright Star K1082 in M15
Authors: Yao Bao-an , Tong Jian-hua , Zhang Chun-sheng
Published: July 2016

We present an analysis of photometry that we and others have obtained of the suspected two–hour variable K1082 in M15.
Spectroscopic Observations of BF Cygni
Authors: Huang C. C. , Chen L.
Published: July 2016

Spectroscopic observations of BF Cygni performed at the Haute-Provence Observatory in 1981 August, October and November are presented. The spectrum of BF Cyg was dominated by strong emission lines of H I, He I, [O III] and [Ne III]. Emission lines of He II and N III were weak. The spectrum of the star displayed dramatic variations during our observations. The intensities of Balmer lines, Balmer continuum and He I lines clearly increased from August to October, while the lines of [Ne III] and [O III] showed inverse variability.
Structure of Molecular Clouds Around some Pre-main Sequence Stars associated with Cometary Nebulae
Authors: Nakano Makoto
Published: July 2016

We present 12CO and 13CO molecular line observations of some pre-main sequence stars associated with cometary nebulae and attempt to unravel their detailed structure.
Misidentified OH/IR Stars
Authors: Lewis B. M. , Hekkert P. te Lintel
Published: July 2016

Plots of periods against (25μm – 12μm) colour of OH/IR stars suggest that four IRAS sources, that have been associated with known OH/IR stars, either provide anomalous identifications, or are weak rather than regular variables. It is argued here that only one of these cases is an association error. OH15.7+0.8 and OH37.1–0.8 are the new proto–planetary nebula candidates.
M Supergiants with Large Infrared Excesses in the Direction of the Galactic Centre
Authors: Raharto Moedji
Published: July 2016

This paper discusses the spatial distribution of M supergiant stars in the Galaxy using infrared data from IRAS.
An Accretion Wave as the Generator of the Great Galactic Ring
Authors: Marochnik Leonid , Suchkov Anatoly
Published: July 2016

This paper discusses the accretion wave phenomenon as a generator of the Great Galactic Ring and the mechanism for forming discontinuities in interstellar gas flows.
Ecliptical Orthogonal Motion and Perihelion Distribution of the AAA Asteroids
Authors: Siregar Suryadi
Published: July 2016

This paper briefly discusses the Aten, Apollo and Amor asteroid types (collectively referred to as AAAs), their perihelion distribution and orthogonal motion. There are 90 objects in these classes: 6 Atens, 46 Amors and 38 Apollos. The maximum distance to the ecliptic plane of each class follows an exponential function.
A Numerical Simulation for the Cooling Process of the Solar Flare Loop
Authors: Gan W. Q. , Fang C. , Zhang H. Q.
Published: July 2016

Extended abstract

We have simulated numerically the hydrodynamic cooling process after the maximum phase of a solar flare with improvements on the chromospheric radiative loss and the resolution of the transition region, together with the introduction of the mechanism of chromospheric heating by coronal soft X-rays. The main results are as follows:

1.

At the early stage of the gradual phase, thermal conduction maintains chromospheric evaporation, but with the cooling of the atmosphere, chromosphere evaporation decreases gradually.

2.

In most of the gradual phase, the velocity is smaller than 40km s−1 in the corona and 4km s−1 in the chromosphere.

3.

From the middle stage of the gradual phase, the coronal atmosphere appears to have a quasi-periodic oscillation. The period is about two minutes, and the amplitude of velocity is within ±20km s−1.

4.

The transition region continues to move downward at first and then changes very slowly for quite a long time. The upward motion of the transition region takes place only at the latest stage, when the atmosphere cools below the quiet-Sun case.

5.

In contrast to the changes of temperature, the density of the corona does not seem to vary until the violent descent of coronal material takes place at the end of the gradual phase.

6.

The coronal part cools mainly by thermal conduction, while the chromospheric part cools by radiative loss. With our initial model, it takes about 25 minutes for cooling from the maximum phase to nearly the quiet-Sun case.

7.

The soft X-ray heating of the chromosphere seems to be of negligible importance in our calculations, but if the coronal density is greater than 1011 cm−3 at the maximum phase of the flare, the soft X-ray heating may play some role in the gradual phase.

8.

At the latest stage of the gradual phase, the atmosphere remains dense and at low temperature. As a further consequence, it would evolve into a post-flare loop.
CCD Observations from the Centre of a City: Use in Astronomical Education
Authors: Lomb N. R.
Published: July 2016

One of the two main telescopes at Sydney Observatory is a computer-controlled 35.6-cm Celestron. It is used with a television-type system. There is an integrating CCD camera available as well as an ordinary TV camera for bright objects. The images from the cameras can be shown in the Observatory’s lecture room. They are first put through an image processor which allows constant enhancement, spatial filtering and the recording of images for use on cloudy nights. Preliminary results are encouraging, and show the value of the system, even in Sydney’s highly light-polluted sky.
Structure within a Magnetic Flux Tube
Authors: Wilson P. R.
Published: July 2016

Since their initial discovery by Hale, the nature of solar magnetic fields has presented us with a number of problems. At one time it was thought that the field consisted of a weak background dipole field of order 1-2 G on which was superimposed the considerably more intense fields associated with active regions and sunspots. However, more recent observational studies by Harvey, Frasier, Stenflo and others have suggested that 90% of the background field appears in the form of intense small-scale fields with intensities of order 103 gauss or greater and which have remarkably similar properties whether they occur in active or quiet regions. In particular, the field intensity appears independent of the total amount of flux present but the appearance of the structure depends critically on the total flux.
Gas Response to a Rotating Stellar Bar
Authors: Schwarz M. P.
Published: July 2016

The arms in spiral galaxies cannot be material arms for then they would wind up on a time scale of one galactic rotation, or a few times 108 years. The large number of spirals suggests that the spiral pattern must persist for about 1010 years (or be continually rejuvenated). The density wave theory treats the spiral pattern as a wave phenomenon, thus overcoming this problem. Much work has been done studying small amplitude oscillations in flat stellar discs. Self-consistent spiral modes have been found, but they are not stable and grow at a fast rate. Numerical simulations of thin stellar discs, such as those of Hohl (1971), which can handle finite amplitude waves, have been more successful. Spiral waves form initially but evolve into a steady state rotating bar. It seems therefore, that a long-lived spiral cannot be formed in stars alone.