bluuebunny/crossref_metadata_2025_split huggingface dataset:
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

AbstractThe 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

AbstractThis 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

AbstractA 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.
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 conditionwhere 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
The ‘High Velocity Cloud’ Origin of the Magellanic System
Authors: Mathewson D. S. , Wayte S. R. , Ford V. L. , Ruan K. 
Published: July 2016

AbstractIt 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

AbstractModel 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

AbstractThe 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

AbstractThis 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

AbstractIt 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

AbstractWe 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

AbstractIn 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

AbstractObservations 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

AbstractThe 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

AbstractDaily 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.
Spectropolarimetry of SN 1987A with the AAT
Authors: Bailey Jeremy 
Published: July 2016

AbstractSpectropolarimetric 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

AbstractOscillatory 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

AbstractDuring 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

AbstractStudies 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.
The Fanaroff-Riley Classification of Southern Extragalactic Radio Sources
Authors: Jones P. A. 
Published: July 2016

AbstractA 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

AbstractWe 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

AbstractContinuous, 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

AbstractWe 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

AbstractA 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.
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

AbstractWe present a list of bright (&lt; 17 mag) southern QSOs and bright (&lt; 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

AbstractMolecular 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

AbstractThe 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

AbstractWe 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.
Estimation of Mass-loss Rates for Some Galactic Wolf Rayet Stars
Authors: Woo Jong Ok 
Published: July 2016

AbstractThe 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

AbstractWe 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.