bluuebunny/crossref_metadata_2025_split huggingface dataset:
A Southern Hemisphere Ammonia Survey
Authors: Peters W. L. , Forster J. R. , Gardner F. F. , Whiteoak J. B. , Kuiper T. B. H. 
Published: July 2016

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

AbstractAdult education classes in astronomy have been conducted in Sydney for many years. The University of Sydney has been especially prominent in this field, holding classes in conjunction with the Sydney WEA prior to 1983, and independently since then. In the last 11 years, most of these courses have been conducted by postgraduate students from the Astrophysics and Astronomy departments in the University’s School of Physics. This paper describes these courses and points out some future possibilities in the teaching of astronomy to adult classes.
The Influence of the Rayleigh and Prandtl Numbers on Convective Heat Transport in Stars
Authors: Murphy J. O. 
Published: July 2016

The two important parameters which essentially determine the nature of the convective regime, and consequently the total heat transported by convective processes, across an unstable layer in a star are the Rayleigh and Prandtl numbers defined by (Chandrasekhar 1961)where ν is the coefficient of kinematic viscosity, x is the coefficient of thermal diffusivity and α, g, d, ΔT are respectively the coefficient of thermal expansion, acceleration due to gravity, depth of the fluid layer and temperature difference across the layer. In addition, the horizontal scale of the convection cell is determined by the horizontal wave number a and for convection to be established R must be greater than the critical value at marginal stability, Rc, which is a function of a, given bywhen the free boundary conditions apply.
Spot Modelling of AB Dor, 1980-1991
Authors: Anders G.J. , Coates D.W. , Thompson K. 
Published: July 2016

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

AbstractAmong the astrophysical researches which will largely benefit from observation from the Antarctic Plateau, we consider those which require high-quality, continuous, daylight, uninterrupted observation in the optical–near-IR region. The systematic study of the stellar micro-oscillations and surface activity of individual objects, as well as of stellar associations extended for periods of weeks, will make a fundamental contribution to our knowledge of stellar structure and will ultimately provide the physical parameters of the stars. A similar consideration applies for the short-period (a few hours to a few days) binaries, which include the W UMa contact binaries. These objects are subject to continuously varying light curves associated with surface activity and secular effects, which cannot be adequately studied from the currently available ground telescopes. Finally, the exceptional seeing and low background will allow the systematic search for and study of supernovae in clusters of galaxies at cosmological distances, which will improve our knowledge of the geometry of the Universe at z ~ 0·7–1.
Sydney Observatory and Astronomy Teaching in the 90s
Authors: Lomb Nick 
Published: July 2016

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

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

AbstractGravitational lensing can significantly magnify the images of astrophysical sources, but only if the source lies within the Einstein ring of the lens. In consequence the chance of any Galactic star magnifying a more distant source is extremely small—much less than one in a million. However, the extra light travel time (‘Shapiro delay’) introduced by the presence of a lens can be large even when there is negligible effect on the image magnification, and as the relative positions of source and lens change so does the delay. In this paper we quantify these changes and the corresponding influence on apparent timing properties of pulsars. While the total Shapiro delay can be large, it is the temporal variations in this quantity which are measurable with pulsar timing. We find that the magnitude of the expected delay variations is too small to be detectable except during strong lensing events, which are extremely rare. Even in the case of a high-velocity pulsar in the Galactic Plane, the stochastic Shapiro delay is typically expected not to have a substantial influence on the timing properties. In consequence the viability of a pulsar-based time standard is not adversely affected by gravitational lensing.
Solar Flares: Implications of the Circuit Model (Invited Paper)
Authors: Melrose D. B. 
Published: July 2016

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