bluuebunny/crossref_metadata_2025_split huggingface dataset:
Associations between Galaxies and Bright Quasars
Authors: Drinkwater M. J. , Webster R. L. , Thomas P. A. , Millar D. 
Published: July 2016

AbstractThe results of a new imaging survey of 68 bright (mv < 18) high redshift (z > 0.7) quasars are presented. The distribution of celestial distances between the quasars and the nearest galaxy neighbours shows an excess at small separations (< 15 arcseconds) significant at the 99.96% level. The redshifts of these galaxies are not known, so two interpretations are possible. If the galaxies are in groups physically associated with the quasars then they must be significantly brighter (> 3 magnitudes) than normal M* galaxies at the present epoch. Alternatively, this may be the result of a bias caused by gravitational amplification of background quasars by compact lenses in the halos of the nearest neighbour (foreground) galaxies. Of the present sample, 25% of the quasars have extra galaxies. If this is caused by a gravitational lensing bias, then, allowing for incompleteness, the results imply that as many as 60% of bright quasars may be gravitationally lensed.
Ring-width Variation in Sub-fossil Wood Samples as an Indicator of Short-term Solar Variability 2000 yr B.P.
Authors: Murphy J.O. , Palmer J.G. 
Published: July 2016

AbstractResults from carbon 14 analysis of Bristle cone pine wood, using samples bounded by decade groups of annual rings, has established a significant long term solar periodicity of just over 200 years. Sites with large quantities of buried sub-fossil Kauri, Huon pine and Celery pine logs, which can provide data for a record possibly exceeding 20 000 years, have been identified in New Zealand and Tasmania. An initial study into periodicities, of possible solar origin, embedded in these ring-index time series can be justified on the basis that there are few other sources of annual proxy data, extending beyond the last 2000 years, that may reflect solar variability. Results from spectral analysis of a sub-fossil floating Celery pine chronology, which extends over 426 years, are considered. Carbon dating indicates that the Taupo volcanic eruption, which buried this forest, occurred about AD 177.
The Formation of Red Giants
Authors: Frost Cheryl , Lattanzio John C. 
Published: July 2016

AbstractThe astrophysical literature contains many discussions on exactly which changes in a star’s structure are responsible for the extremely large radii found after core hydrogen exhaustion. Different authors favour different mechanisms. Unfortunately none of the proposals are easily verified nor are they easily disproven. In this paper we examine the suggestion that it is the increased central mass concentration (i.e., the growth of the hydrogen exhausted core) which is the primary agent responsible for envelope growth.
Searching for Supernovae—Visually and Otherwise
Authors: Evans Rev. Robert 
Published: July 2016

AbstractThe main features of visual searching for supernovae in other galaxies by amateur astronomers are described, and an outline is given of the results which have been achieved so far by this method. A short comparison is made between visual searching and photographic searching. A more extensive comparison is then made between visual searching for supernovae in Australia, and the work of the Berkeley Automatic Supernova Search at Leuschner Observatory, since 1986. Among the conclusions is the claim that a competent visual observer could produce similar results to those produced by the Berkeley group if a telescope of similar aperture was used for a similar amount of observing time, and from a good observing site. Indeed, visual searching might possibly produce more results, and such a search would only cost a small fraction of what was spent on this automatic search. It would be a worthwhile project to conduct a visual search with a suitably designed 76-cm telescope, or a one metre telescope, over a period of a few years, to see if this conclusion could be supported in practice.
Reversal of the Sense of Polarisation in Solar and Stellar Radio Flares
Authors: Melrose D. B. , Robinson P. A. 
Published: July 2016

AbstractIt is shown that numerical integration of the equation of polarisation transfer for generalised Faraday rotation provides an alternative to mode-coupling theory for treating propagation through a quasi-transverse (QT) region. At a QT region, where the sign of the component of the magnetic field along the ray path reverses, the sense of circular polarisation reverses below a frequency ωt, and is unchanged above ωt. There is a long-standing difficulty in the interpretation of the polarisation of radio emission from bipolar regions on the Sun: observational and theoretical estimates of ωt appear inconsistent. The alternative approach may help resolve this difficulty.
Shock Drift Acceleration and Type II Solar Radio Bursts
Authors: Street Arthur G. , Ball Lewis , Melrose D. B. 
Published: July 2016

AbstractShock drift acceleration of the electrons which produce herringbone structure in type II bursts is considered. A non-coplanar component of the magnetic field within the shock front and an electric field across the shock are taken into account. A quantitative difficulty with shock drift acceleration is identified, and possible ways of overcoming the difficulty are outlined.
The Cosmic Ray Ground-level Enhancement of 24 October 1989
Authors: Cramp J. L. , Humble J. E. , Duldig M. L. 
Published: July 2016

AbstractThe cosmic ray ground-level enhancement (GLE) of 24 October 1989 was the last of a series of GLEs associated with the same solar active region. Intensity enhancements were observed by at least 31 neutron monitors in the worldwide network, with the largest increase (~200%) observed at South Pole, Antarctica around 20:30 UT. Using a least-squares model fit to all available neutron monitor data, spectra, apparent source directions and particle pitch angle distributions have been derived. The effect of disturbed geomagnetic conditions has also been taken into account.
Increasing the Field Size of the Molonglo Observatory Synthesis Telescope
Authors: Large M. I. , Campbell-Wilson D. , Cram L. E. , Davison R. G. , Robertson J. G. 
Published: July 2016

AbstractThe Molonglo Observatory Synthesis Telescope (MOST), which at present images a fully synthesised 70′ field in 12 h, is being converted to enable observing modes which extend the field size to 160′. The new observing modes will allow the MOST to survey completely the sky south of δ = −30° to a (5σ) sensitivity limit of about 5 mJy. The result will be a catalogue of over 400,000 radio sources with a spatial density of less than 1 source per 100 beam areas, providing the foundation for a number of novel astronomical and cosmological investigations. The conversion involves construction of 352 low-noise HEMT preamplifiers, 88 digitally controlled UHF quad phase shifters, 88 mixers and IF sections, a new communication and control system, and several other new sub-systems. The project has been funded and developments are well advanced.
Magnetic Fields and Shocks in Molecular Clouds
Authors: Byleveld S. E. , Melrose D. B. , Pongracic H. 
Published: July 2016

AbstractWe discuss the expected properties of shocks in molecular clouds when the effect of a magnetic field is included. The results suggest that shocks should have magnetic precursors, and may be C-shocks rather than J-shocks, but the observations are not obviously consistent with this prediction. The effect of these shock properties on cloud collisions triggering star formation is discussed.
How Similar are Type Ia Supernovae?
Authors: Stathakis Raylee A. , Sadler Elaine M. 
Published: July 2016

AbstractWe have compared the spectra of six Type Ia supernovae, at ages between 4 and 404 days after maximum light, to see whether all show similar evolutionary behaviour. We find that the spectral lines between 6800 Å and 8000 Å follow a smooth evolutionary trend, but that lines redward of 8000 Å show significant differences. SN 1987I and SN 19880 show extra emission over a broader wavelength region, possibly due to OI 8446 Å emission which would indicate higher envelope densities for these objects. Our results are consistent with the trend of expansion velocity with parent galaxy type reported by Branch and van den Bergh (1993). Variations within the class of Ia SNe may affect their use as standard candles.
Diffusive Shock Acceleration by Multiple Shock Fronts with Differing Properties
Authors: Pope M. H. , Melrose D. B. 
Published: July 2016

AbstractThe effect of diffusive shock acceleration on a distribution of particles is explored for multiple shocks, taking into account adiabatic expansion between the shocks. Specifically, the spectral index is calculated numerically for two cases: a sequence of identical shocks, and a sequence of pairs of shocks with alternating shock strength. How these two cases evolve to the asymptotic limit is examined, and it is shown that the evolution of the paired-shock case can be described by a sequence of identical shocks with shock strength equal to the mean of the two.
Accretion Geometry of Synchronously Rotating Magnetic Cataclysmic Variables: Theories versus Observations
Authors: Wu Kinwah , Wickramasinghe D. T. , Bailey J. , Tennant A. F. 
Published: July 2016

AbstractWe review the magnetic locking of the white dwarf and the companion star in AM Herculis-type binaries for various white dwarf magnetic field structures, and compare the theoretical results with observations. The model in which the white dwarf has a dipole plus a quadrupole field is found to be in closest agreement with the recent observations.
An H I Mosaic of the Small Magellanic Cloud
Authors: Staveley-Smith L. , Sault R. J. , McConnell D. , Kesteven M. J. , Hatzidimitriou D. , Freeman K.C. , Dopita M. A. 
Published: July 2016

AbstractThis paper describes the first results from a 20 deg2 mosaic of the Small Magellanic Cloud (SMC) in the λ21-cm line of neutral hydrogen. The mosaic consists of 320 separate pointings with the 375-m array of the Australia Telescope Compact Array. The angular resolution is 1′· 5 (26 pc, for a distance of 60 kpc) and the velocity resolution is l·6kms−1. The images reveal a structure of remarkable complexity, with much of the spatial power contained in high-brightness temperature compact knots and filaments. Numerous wind-blown ‘bubbles’ and ‘supershells’ are evident in the data, both inside and outside the stellar confines of the SMC. Some high-density H I regions are seen to correlate with Hα regions, indicating sites of current star formation. However, many high-column-density H I regions are devoid of optical emission and may represent regions of future star formation. These regions may be under-abundant in diffuse molecular gas due to the high radiation field and low metallicity of the SMC.
Multi-wavelength Observations of Galactic Winds
Authors: Bland-Hawthorn J. 
Published: July 2016

AbstractIt has long been suspected that winds of thermal and/or relativistic particles are a common feature of both active and normal galaxies. Galactic winds are likely to be an important mechanism, particularly at high redshift, by which energy and metals from galaxies are subsequently dumped into the intergalactic medium. Both observational and theoretical studies of wind processes remain in their infancy, largely because astrophysical winds are difficult to detect. Future satellite missions will make systematic surveys possible for the first time. In this review, we summarise the current evidence for galactic-scale winds, particularly in energy bands where the wind emission is spatially resolved. We also discuss observational limitations and problems of interpretation.
Solar Second Harmonic Plasma Emission and the Head-on Approximation
Authors: Willes A. J. , Robinson P. A. , Melrose D. B. 
Published: July 2016

AbstractThe coalescence of two Langmuir waves, L and L′, produces emission at twice the plasma frequency in type II and type III solar radio bursts. The analysis of the coalescence process is usually simplified by assuming the head-on approximation, where the wavevectors of the coalescing waves satisfy kL′ ≈ −kL, corresponding to the two Langmuir waves meeting head on. However, this is not always a valid approximation, particularly when the peak of the Langmuir spectrum lies at small wavenumbers, for narrow band spectra, and for spectra with broad angular ranges. Realistic Langmuir wave spectra are used to investigate the effects of relaxing the head-on approximation.
Asteroid Discovery Efficiencies for Telescope Systems at Siding Spring
Authors: Steel Duncan 
Published: July 2016

AbstractRelative efficiencies for the discovery of Earth-crossing asteroids (ECAs) are modelled for various telescopes at Siding Spring. It is found that the narrow-field instruments—the Anglo-Australian Telescope and the 40 in and 2·3m reflectors—are not competitive in this regard for present CCD imaging systems. The UK Schmidt Telescope (UKST), if used to take short-exposure stereo pairs of photographs, would be an effective search tool, outperforming all current systems apart from the Ground-based Electro-Optical Deep Space Surveillance (GEODSS) systems now being implemented by the US Air Force for ECA searches. If a CCD mosaic were fitted to the UKST, its performance would far exceed that of any other device at Siding Spring, and it would produce ECA discoveries at a rate around 3–4 times as high as GEODSS, but at considerable expense. The most sophisticated search instrument currently in use is the University of Arizona’s Spacewatch telescope; a notable result found here is that even with its present CCD, the Automated Patrol Telescope (APT) of the University of New South Wales would be able to match or outperform Spacewatch for all ECA sizes, including ~10m objects, should this modelling be a reasonable representation of its real performance. In terms of cost-effectiveness and telescope availability, the conclusion arrived at herein is that the APT, equipped with small-pixel but large-format CCD chips of high quantum efficiency, would be an extremely effective ECA search instrument: if operated with 12 μm pixel chips covering a 4° × 4° field it might produce ECA discoveries at a rate well in excess of the combined rate for all current search programs.
Using the COSMOS/UKST Southern Sky Object Catalogue
Authors: Drinkwater Michael J. , Barnes David G. , Ellison Sara L. 
Published: July 2016

AbstractA complete copy of the compressed COSMOS/UKST Southern Sky Object Catalogue is now available on-line at the Anglo-Australian Observatory and the Australia Telescope National Facility. The catalogue lists image parameters for all objects detected to a limit of BJ ≈ 21·5 in the UK Schmidt Southern Sky Survey. We have written software to access the catalogue efficiently and generate finding charts or text listings of the image parameters. In this paper we describe the software and give some examples of its use. We also discuss the astrometric precision of the catalogue.
An Automated DIMM Telescope for Antarctica
Authors: Dopita Michael A. , Wood Peter R. , Hovey Gary R. 
Published: July 2016

AbstractA knowledge of the on-ice seeing is a key requirement for planning future Antarctic observatories. In this paper we discuss the likely negative impact on seeing produced by the development of the deep winter surface temperature inversion (Ekman layer). The Automated Astronomical Site Testing Observatory (AASTO) will deploy, as one of its complement of site-testing instruments, an automated differential image motion monitor (DIMM) telescope designed to generate seeing data throughout the Antarctic winter. Here we describe the multi-aperture concept which has been developed for this mission, and touch upon some of the critical technological considerations associated with the low power budget and with the requirement of autonomous operation at very low temperature (–90°C).
POST: A Polar Stratospheric Telescope for the Antarctic
Authors: Dopita Michael A. , Ford Holland C. , Bally John , Bely Pierre 
Published: July 2016

AbstractThe tropopause, typically at 16 to 18 km altitude at the lower latitudes, dips down to only 8 km in the polar regions, allowing access to the cold, dry and nonturbulent lower stratosphere by tethered aerostats. These can float as high as 12 km, have long operating lifetimes, and are extremely reliable. In contrast to free-flying balloons, they can stay on station for weeks at a time, and payloads can be safely recovered for maintenance and adjustment and relaunched in a matter of hours. We propose to use such a platform, located first near Fairbanks, Alaska, and later in the Antarctic, to operate a new-technology 4 m telescope with diffraction-limited performance in the near infrared. Thanks to the low ambient temperature (~200 K), thermal emission from the optics is of the same order as that of the zodiacal light in the 2–3 μm band. Since this wavelength interval is the darkest part of the zodiacal light spectrum from optical wavelengths to 100 μm, the combination of high-resolution images and a very dark sky make it the spectral region of choice for observing galaxies, QSOs and clusters of galaxies at the formation epoch of galaxies.
Educational Outreach Programs at the Center for Astrophysical Research in Antarctica
Authors: Sweitzer J. S. , Brass C. , Harper D. A. , Hawkins L. , Kron R. G. , Whitt A. S. 
Published: July 2016

AbstractThe Center for Astrophysical Research in Antarctica conducts various educational outreach programs as part of its mission as a National Science Foundation Science and Technology Center. The method behind the outreach programs is one of forging partnerships between Center researchers and other educational organisations. The main program serves primary and secondary students in Chicago. The core of the program is called Space Explorers and is targeted at high school students. These students attend a summer residential institute at the University of Chicago’s Yerkes Observatory. The high school Space Explorers then extend the reach of the program during the academic year by teaching in primary schools using a portable planetarium. The Center also pursues many other outreach activities and is in the process of forming an Antarctic Education Alliance.
SPH Simulations of Accretion Disks and Narrow Rings
Authors: Maddison Sarah T. , Murray James R. , Monaghan Joe J. 
Published: July 2016

AbstractWe model a massless viscous disk using smoothed particle hydrodynamics (SPH) and note that it evolves according to the Lynden-Bell & Pringle (1974) theory until a non-axisymmetric instability develops at the inner edge of the disk. This instability may have the same origin as the instability of initially axisymmetric viscous disks discussed by Lyubarskij, Postnov & Prokhorov (1994). To clarify the evolution we evolved single and double rings of particles. It is actually inconsistent with the SPH scheme to set up a single ring as an initial condition because SPH assumes a smoothed initial state. As would be expected from an SPH simulation, the ring rapidly breaks up into a band. We analyse the stability of the ring and show that the predictions are confirmed by the simulation.
Accretion Phenomena in Cataclysmic Variables
Authors: Bailey Jeremy 
Published: July 2016

AbstractThe processes of accretion onto the white dwarf in a cataclysmic variable are reviewed. These systems provide the most easily observable examples of accretion disks, and enable the structure of the accretion region to be studied in detail. The properties of column accretion onto magnetic cataclysmic variables are also described.
The Jets in Radio Galaxy B1308–441
Authors: Jones Paul A. 
Published: July 2016

AbstractThe giant radio galaxy B1308–441 has prominent two-sided jets, typical of Fanaroff–Riley class I radio galaxies, but there is an unusual bright spot in the SE jet 2 arcmin from the core that gives a marked asymmetry to the source. Observations at 1·37 and 2·37 GHz with the Australia Telescope Compact Array show that the bright spot has a flattened spectrum and high polarisation, and changes the direction of the SE jet. There is a diffuse optical object close to the bright spot which may be related to a shock in the jet.
Angular Pointing and Guidance for the Sydney University Stellar Interferometer
Authors: Tango W. J. , Thorvaldson E. D. 
Published: July 2016

AbstractThe Sydney University Stellar Interferometer (SUSI) uses siderostats (plane, alt–azimuth mounted mirrors) to reflect starlight into the instrument. The analysis of the pointing and guidance of the siderostats by traditional methods is not practical and vector algebra has been used to develop the required algorithms. Real siderostats will not be ideal and can be modelled by a set of parameters. The methods for determining the model parameters and for incorporating them into the guidance and pointing algorithms are described. Field rotation also affects the operation of SUSI, and the field rotation angle and related quantities are also determined.
A Simple Model of a Coronal Hole
Authors: Summers D. 
Published: July 2016

A coronal hole is a region of the solar corona characterised by diverging magnetic fields of single polarity and lower-than-average densities (and probably temperatures). It is now generally accepted that coronal holes are the source of high-speed streams in the solar wind (Munro and Withbroe 1972, Kopp and Holzer 1976, Steinolfson and Tandberg-Hanssen 1977, Munro and Jackson 1977; see Pneuman 1980 for references to most of the theoretical and observational papers on coronal holes since their recognition in 1968). We consider an infinitesimal field-aligned flow tube with cross-sectional area A(r) where r is the heliocentric radius (Figure 1), and we adopt the functional formA(r)/A(r ) = (r/r0)8where r is the coronal base radius, and 5 is a parameter which measures the divergence of the flow. If s = 2 then the flow is purely spherically symmetric, while if s > 2 the flow is more strongly divergent as is expected to be the case for a coronal hole. The cross-section of a typical coronal hole is shown schematically in Figure 2.
A search for prompt ultra-high-energy gamma rays from supernova 1987a
Authors: Bird D. J. , Bruce T. E. G. , Ciampa D. , Clay R. W. , Corani C. L. , Edwards P. G. , Gregory A. G. , Patterson J. R. , Protheroe R. J. 
Published: July 2016

AbstractA search has been made using the Buckland Park air shower array for evidence of any excess of events from the direction of the recent supernova in the Large Magellanic Cloud. Upper limits resulting from this search and their significance are discussed in this paper.