bluuebunny/crossref_metadata_2025_split huggingface dataset:
Supernova Remnants in the Large Magellanic Cloud
Authors: Dickel John R. , Milne D. K. 
Published: July 2016

AbstractTwelve supernova remnants in the Large Magellanic Cloud have now been observed with the Australia Telescope. These were all imaged in total intensity and where possible the linear polarisation was also mapped. In many respects this survey is similar to previous single-dish observations of Galactic supernova remnants, and comparisons are made with these results. Preliminary images are shown for several sources. The survey is continuing with additional array configurations and at other wavelengths.
Peculiar Gas Dynamics in the Starburst Galaxy NGC 253
Authors: Koribalski Bärbel , Whiteoak John B. , Houghton Sally 
Published: July 2016

AbstractHere we present our first results of a study of the neutral hydrogen gas (HI) in the southern spiral galaxy NGC 253 with the Australia Telescope Compact Array. The relative proximity of NGC 253 makes it a very suitable object for detailed studies of large-scale, as well as nuclear, gas dynamics. Several peculiar features have been found. The HI distribution is asymmetric in the outer regions, probably as a result of the strong warping of the spiral arms. A bar associated with the disc, clearly visible in the optical and near-infrared, also reveals its signature in the neutral hydrogen gas. HI absorption measurements reveal unusual motions of the gas in the nuclear region which seem to indicate a fast-rotating ring of cold gas as well as outflow of gas. Similar features have been found in other starburst galaxies, such as M 82, NGC 1808 and NGC 4945, and are interpreted in terms of bar-induced gas dynamics and star formation.
Feedback Mass Transfer in Cataclysmic Variables: An Explanation of the Behaviour of VY Scl Stars
Authors: Wu Kinwah , Wickramasinghe Dayal T. , Warner Brian 
Published: July 2016

Abstract We investigate irradiation-driven mass transfer in cataclysmic variables in the presence of shielding of the radiation by an accretion disk. We have shown that the shielding can cause a temporal drop of 3–5 magnitudes in the brightness of systems with orbital periods shorter than about 4 hr. This provides a possible explanation for the brightness variations in the VY Scl stars.
The Magnetic Field of 1H1752+08
Authors: Ferrario Lilia , Wickramasinghe Dayal T. , Bailey Jeremy , Buckley David 
Published: July 2016

AbstractWe present spectropolarimetric observations of the eclipsing cataclysmic variable 1H1752+08. Modelling of the line intensity and polarisation spectra of 1H1752+08 shows that the magnetic field structure of the white dwarf is off-centre and the mean photospheric field strength is about 7 MG, the lowest measured in a cataclysmic variable (CV). We argue that 1H1752+08 is most probably a low-field AM Herculis system.
Effects on Seeing at the Anglo-Australian Telescope of Temperature Differences between Outside Air, Dome Air and Mirror
Authors: Wood P. R. , Ryan S. G. 
Published: July 2016

AbstractSeeing measured in the open air with a differential image motion monitor (DIMM) is compared with seeing measured simultaneously at the Cassegrain focus of the Anglo-Australian Telescope (AAT). It is shown that when the mirror is hotter than the dome air, the AAT’s seeing is degraded by ~1 arcsec per Celsius degree of excess mirror temperature. The consequence of this is that mirror seeing currently contributes significantly to the seeing at the AAT on many nights. A mirror colder than the dome air does not seem to degrade seeing, and neither does an internal-to-external air temperature difference of up to at least 3°C when the venting fans are on.
Dark Matter: Abstracts from a Two-day Workshop held in February 1994 by the Australia Telescope National Facility
Authors: Koribalski Bärbel 
Published: July 2016

Summary A Dark Matter Workshop was held at the CSIRO Radiophysics Laboratory in Marsfield, Sydney, on 24–25 February 1994. The workshop, sponsored by the Australia Telescope National Facility (ATNF), was a meeting of dark matter (DM) specialists as well as astronomers interested in the field, and attracted about 80 participants from nine institutions. The program consisted of 22 oral contributions (15–45 minutes), followed by lively discussions, as well as podium discussions at the end of each day. Abstracts of most of the contributions are presented here, arranged by subject groups which range from ‘Gravitational Lensing and DM in Clusters’, ‘DM in Elliptical Galaxies’, ‘The Nature of DM’, and ‘The Shapes of Dark Halos’ to ‘Alternatives to DM’.
Visualisation of Radio Data
Authors: Oosterloo Tom 
Published: July 2016

AbstractRadio astronomy software has not quite kept up with recent developments for the display of, and interaction with, data. At the Australia Telescope National Facility we are trying to catch up by investigating how useful visualisation techniques and approaches like visual computing are for the reduction of radio data. I will discuss a few techniques that we have applied to radio data and comment briefly on their merits.
JACARA’s Plans
Authors: Burton Michael G. , Ashley Michael C.B. , Storey John W. V. , Dopita Michael A. , Lançon Adriane , Mould Jeremy , Wood Peter R. , Hall Peter , Duldig Marc 
Published: July 2016

AbstractThe plans of JACARA, the Joint Australian Centre for Astrophysical Research in Antarctica, for Australian involvement in future astronomical activities on the antarctic plateau, are outlined.
An Automated Astrophysical Observatory for Antarctica
Authors: Storey J. W. V. , Ashley M.C.B. , Burton M. G. 
Published: July 2016

AbstractConditions on the high Antarctic Plateau would appear to be extremely favourable for a wide range of astronomical research. Before a decision can be made on constructing an observatory, data are required on site conditions at the most promising locations. To enable these data to be collected, a Lockheed Automated Geophysical Observatory is being purchased. This facility will be fitted with a suite of astronomical site-testing instruments, and deployed to several sites on the Antarctic Plateau. This program will allow a definitive assessment of the site conditions to be made by the end of this century.
Accretion Curtains in Magnetic CVs
Authors: Ferrario Lilia 
Published: July 2016

AbstractWe have carried out calculations to model the hydrogen emission line spectrum of intermediate polars with accretion disks. We show that we can explain most of the observed optical continuum and line fluxes in terms of hard and soft X-rays that originate from the accretion shocks and are reprocessed in curtains formed by magnetically channelled material.
Simulations of Quasi-periodic Oscillations in Accreting White Dwarfs
Authors: Wu Kinwah , Pongracic Helen , Chanmugam Ganesar , Shaviv Giora 
Published: July 2016

AbstractThe stability of accretion shocks in magnetic white dwarfs is investigated. Shock oscillations are simulated numerically, and in the simulations bremsstrahlung and cyclotron cooling are considered in an explicit form. We have found that for shocks with magnetic fields lower than 10 MG, shock oscillations can be sustained; while for magnetic fields greater than 20 MG, the oscillations are suppressed.
Langmuir Wave Emission by Neutrinos in a Medium
Authors: Hardy S. J. , Melrose D. B. 
Published: July 2016

AbstractExpressions for the probability per unit time of the emission of a Langmuir wave by both massive and massless neutrinos moving in a medium are derived using finite-temperature field theory. A comparison between this process and the analogous emission from an electron is made, and possible implications of this process for the explosion mechanisms of type II supernovae are briefly discussed.
Axel: A Balloon-borne X-ray Astronomy Experiment
Authors: Sood R. K. , Panettieri J. , Grey D. , Woods G. , Hoffmann J. , Manchanda R. K. , Staubert R. , Kendziorra E. , Rochester G. K. 
Published: July 2016

AbstractFollowing a successful program to investigate the physics of ultra-high-pressure proportional counters, a counter array has been developed for hard X-ray astronomy. A parallel investigation has evaluated the performance of a large-area phoswich scintillator detector for the same purpose. The two detectors have been integrated in a balloon-borne payload, the Astrophysical X-ray Experimental Laboratory (AXEL). This paper describes the instrumentation aboard the payload.
Millimetre-wave Astronomy: Abstracts from a One-day Workshop held on 19 April 1995 at the Australia Telescope National Facility
Authors: Koribalski Bärbel 
Published: July 2016

SummaryA Millimetre-wave Astronomy Workshop was held at the CSIRO Radiophysics Laboratory in Marsfield, Sydney, on 19 April 1995. The workshop, sponsored by the Australia Telescope National Facility (ATNF), was a meeting of mm-wave specialists as well as astronomers and students interested in the field, and attracted about 80 participants from 13 institutions. The program consisted of 23 oral contributions (5–45 min) followed by lively discussions. Abstracts of most of the contributions are presented here, arranged by groups dealing with subjects such as ‘A Basic Introduction’, ‘Astronomy in the mm-range with Mopra’ and ‘Projects: Galactic and Extragalactic 3 mm-wave astronomy’.
Millimetre Continuum Observations of AGNs and IRAS Galaxies
Authors: Norris Ray 
Published: July 2016

The 3 mm radio continuum emission from active galaxies consists of three components:
(1)Synchrotron emission from the active galactic nucleus (AGN), which is over 1 Jy in 3C273 but which is not significant in most of the types of galaxy considered here.(2)Free–free emission from H II regions. The flux of this in a starburst galaxy is typically of the order of 10 mJy and could be imaged with a 3 mm-capable Australia Telescope Compact Array (ATCA).(3)Emission from the tail of the 50–100 K black-body spectrum of the dust. For example, the dust in Arp 220 (redshift of 0·02) at a temperature of 50 K has a flux of 30 mJy at 3 mm. Interestingly, this flux does not decrease substantially with redshift, as the decrease in brightness is compensated for by the redshifting of the steep edge of the blackbody curve, and so infrared-bright galaxies can be studied up to high redshifts with existing instruments.
Changes in the Period of the Eclipsing System AH Virginis
Authors: Kennedy H.D. 
Published: July 2016

Guthnick and Prager (1929) were the discoverers of the variability of AH Virginis. Prager (1929) produced a photographic light curve the same year. Lause (1934, 1935, 1937) observed the system visually and improved the period as deduced by Prager. Further visual work on the system was done by Zessewitsch (1944). The first photoelectric observations came from Huruhata and Nakamura (1951), followed in 1952 by Kitamura, Tanabe and Nakamura (1957).Lack of their data on ingress and egress at primary eclipse resulted in the mean curve showing a rounded bottom during minimum light. From this, an inclination of the system of 61° was derived by Kopal and Shapley (1956). Two years later, Kwee (1958) revealed primary minimum to be flat bottomed; the light remaining constant for some 40 minutes. This was confirmed by Binnendijk (1960), thus classifying AH Virginis as one of the few W UMa systems which display complete eclipses at an inclination likely to be closer to 90° then to 61°. Observations of the present study confirm constancy of light of 40 minutes duration during primary minimum. Assuming i = 90°, a new orbital solution was derived by Kitamura and Takahashi (1959) showing constant light for both minima. Binnendijk’s observation, however, showed a curved appearance at secondary minimum. The present observations indicate curved as well as flat secondary minima.
Global Value of Hubble Constant
Authors: Visvanathan N. 
Published: July 2016

An accurate determination of the global Hubble Constant needs distance to objects well outside the Local Supercluster with redshift greater than ~ 2000 km/s. This is mainly to reduce the effect of the peculiar motion of the Local Group on the measured redshifts as well as to get away from the gravitational influence of the nearby high density regions.The present practice of deriving distances involves identifying objects such as Cepheids and brightest red stars both in the Local Group galaxies as well as in the distant galaxies. This method cannot be used for galaxies at the large distances.
Global Oscillations in Late-Type Stars (Invited Paper)
Authors: Cram L. E. 
Published: July 2016

AbstractThe advent of new techniques to measure the global oscillation spectrum of the Sun has provided a new and powerful tool to investigate solar structure. One of the most challenging and potentially rewarding problems in contemporary astronomy is to devise techniques which will allow similar studies of other stars. This paper outlines the theory of global oscillations of late-type main-sequence stars, and summarises some of the achievements of global oscillation studies of the Sun. It then reviews the very few successful attempts that have been made to study stellar oscillations, and briefly discusses several apparently promising lines for further instrumental development.
843 MHz Emission from the Active Star AB Dor
Authors: Beasley A. J. , Large M. I. , Vaughan A. E. 
Published: July 2016

AbstractThe Molonglo Observatory synthesis telescope has been used to obtain twelve observations of a 23′ arc field containing the active star AB Dor. On each occasion, an unresolved source close to the optical position of AB Dor was observed. The source exhibits day-to-day variations of flux density, with a mean value of ∼4 mJy. The identification of the source with the star and the variations in emission are discussed.
Evolution of the Precursor of SN1987A
Authors: Wood P. R. , Faulkner D. J. 
Published: July 2016

AbstractEvolutionary calculations have been made for a star of initial mass 17.5 M⊙ in order to emulate the evolution of the precursor of SN1987A. The results give good agreement (i) with the observed properties of Sanduleak -69°202 (star 1) when the model reaches the supernova epoch, and (ii) with the observed distribution of red and blue supergiants in the LMC. Mass loss throughout the life of the star at rates reasonably consistent with observed values is required to produce these results. At the time of explosion, the supernova has a mass of only ∼ 5.4 M⊙ and it is surrounded by about 8 M⊙ of wind material in a shell of ∼0.4 pc radius.
The Effect of Magnetic Field Spread and Temperature and Density Variations in Cyclotron Emission Regions
Authors: Wickramasinghe D. T. , Ferrario Lilia 
Published: July 2016

AbstractWe discuss the properties of cyclotron radiation from accretion shocks located above the atmospheres of magnetic white dwarfs taking into account the effects of field spread and density and temparture structure. The models which are an improvement on previous point source models are shown to have characteristics that are in better overall agreement with the properties of AM Herculis type systems. Our calculations of the polarization properties of large polar cap emission regions are used to discuss the recent null measurements of circular polarization in DQ Herculis type systems.
Electron Scattering in Cyclotron Emission Regions
Authors: Meggitt S. M. A. , Wickramasinghe D. T. 
Published: July 2016

AbstractThe polarization properties of cylindrical magnetic accretion columns are calculated allowing for electron scattering within the emission region. The results are used to estimate the effects of electron scattering and geometry on the observed properties of AM Herculis type systems.
A Highly Excited Ammonia Cloud at least 300 pc from the Galactic Centre
Authors: Gardner F. F. , Boes F. 
Published: July 2016

AbstractA cloud with a l.s.r. velocity of ∼ 160 km s-1 and a half-width of ∼ 25 km s-1 was mapped in the (1,1), (2,2) and (4,4) lines of para NH3 and the (3,3) and (6,6) lines of ortho NH3 using the 40″ arc beam of the 100-m Effelsberg telescope. The cloud was extended some 5′ in latitude and contained a central concentration ∼ 1′.5 in size at ℓ = 1°.59; b=0°.01. Line temperatures of the four higher transitions define a rotational temperature of ∼ 120 K, while the (1,1) and (2,2) alone yield the lower value of ∼ 40 K. The high temperatures, well above that of the dust, are too high to be caused by collisions with H2 molecules in the ground state, but might result from collisions with H2 in excited states. On a (ℓ, v) plot the cloud does not coincide with any generally accepted galactic centre feature but it is possibly located near the periphery of the ‘rotating nuclear disk’, where conditions would be favourable for the production of shocks, excited H2 and possibly high NH3 temperatures.
Ammonia Mapping of the Southern Molecular Cloud NGC 6334
Authors: Forster J. R. , Whiteoak J. B. , Gardner F. F. , Peters W. L. , Kuiper T. B. H. 
Published: July 2016

AbstractThe Parkes 64-m antenna has been used to map ammonia emission in the (J,K = 1,1) and (J,K = 2,2) transitions toward molecular cloud complex NGC 6334. This complex contains a number of OH and H2O masers, HII regions and IR sources, and is a rich source of molecular line emission.Distributions of observed and derived quantities are presented with a linear resolution of ∼ 1 pc. Velocity anomalies are present near the two OH masers NGC 6334A and B, and the source of ammonia emission located near the northernmost H2O maser is one of the most intense sources of NH3 emission in the Galaxy.
Multiwaveband Studies of X-ray Selected Active Galactic Nuclei
Authors: Brissenden R. J. V. , Tuohy I. R. , Remillard R. A. , Buckley D. A. H. , Bicknell G. V. , Bradt H. V. , Schwartz D. A. 
Published: July 2016

AbstractWe report on the identifications of 15 new X-ray selected Active Galactic Nuclei (AGN). The AGN have been discovered during an ongoing program to identify and study the optical counterparts of X-ray sources detected by the HEAO-1 satellite. The new AGN add to our existing data base of 26 making a sample of 41 objects which are the subject of a multiwavelength study including radio, infrared, optical, UV and X-ray observations. As part of this study 8.4 GHz flux measurements have been made at Parkes. Radio-optical-X-ray continuum spectral index comparisons are presented.
Science with the Australia Telescope (Invited Paper)
Authors: Robinson B. J. 
Published: July 2016

AbstractThe research now under way with the real-time 275 km Parkes-Tidbinbila interferometer is used as a guide to the initial science to be undertaken with the 319 km Australia Telescope (AT) Long Baseline Array. On the other hand, it is risky to guess at the new science likely to be attempted with the 6 km AT Compact Array at Culgoora; instead the potential that has been built into this array is discussed and a selection of basic questions in astrophysics is posed as a guide to significant science that might yield to new observers on a fresh instrument under the southern skies. In conclusion two questions are probed: Can discoveries be made by users of national facilities? Does the AT cross into new domains in the phase space of observations?
Spectral Analysis of SN 1987A: the First 7 Months
Authors: Höflich P. 
Published: July 2016

AbstractModel calculations for the photospheres of SN 1987A are presented. Spherical symmetry and density profiles are assumed to be given by the homologous expansion of the stellar structure of a B3I supergiant. For later stages the density slopes are determined. For a number of elements (H, He, C, N, O, Ne, Na, Mg, K, Ca, Ba) detailed atomic models are used. The statistical equations and the radiation transport are treated consistently as well for the lines as for the continua. In addition, line blanketing due to other elements are included under the assumption of pure scattering. The importance of a sophisticated NLTE-treatment is demonstrated. Chemical metal abundances are derived by comparing the observed and synthetic spectra. Good agreement is found if a third of solar abundance for all elements with the exception of the s-process elements is assumed. An overabundance of He by a factor of 1-2 is indicated by the models corresponding to the time before June 87. No gradient in the chemical abundances of the hydrogen rich layers has to be assumed. Up to October 87 the He abundance at the photosphere is increased to 5 times solar, i.e. the continua are formed in helium rich layers. The chemical profile indicates strong mixing processes of the different layers of the progenitor during the explosion. Additionally, pecularities of hydrogen line profiles are discussed. Mainly, they can be understood by selective line blanketing effects. The total mass of the hydrogen rich shell is estimated to amount to be 9-11 M⊙.
Observations of SN 1987A in the Mid-infrared
Authors: Aitken D.K. 
Published: July 2016

AbstractMid-infrared spectroscopic data on SN 1987A are reviewed. This spectral region contains the fine structure lines of a number of ions, incuding the iron group elements, together with recombination lines of hydrogen and helium. From about 9 months all these lines and the continuum have been effectively optically thin, and the [CoII] line strength and development yields an estimate of the parental 56Ni mass of 0.071 M⊙, very similar to the light curve estimates. At one year after the explosion the velocities appropriate to the hydrogenic and ionic regions are ∼ 2000 km s−1 and ∼ 1500 km s−1, respectively.Apart from an excess between 8–9 μm which appears to be due to molecular SiO, there is no evidence of departure of the continuum from free-free emission, and no sign of any emission from dust. From the free-free continuum an ionization fraction of a few percent is derived for the hydrogen/helium envelope; this provides relative transparency in the mid infrared while the bound electrons provide the X and γ-ray opacity which is still considerable at 15 months.The appearance of neutral ions at 15 months indicates that the ejecta temperatures are cooling, and that dust formation may be imminent.
The Circumstellar Emission from SN 1987A
Authors: Fransson Claes 
Published: July 2016

AbstractIn the first part the UV and optical observations of the circumstellar gas of SN 1987A are reviewed, and the physical properties of the gas discussed. In the second part models of the emission are treated, as well as their use as a diagnostic of the radiation from the supernova during the first, unobserved hours after the explosion.
AAT Observations of the Interstellar Medium towards SN 1987A
Authors: Pettini M. 
Published: July 2016

AbstractThe exceptional brightness of SN 1987A has provided a unique opportunity to probe intervening gas clouds in the disk and halo of our Galaxy and in the Large Magellanic Cloud, as well as intergalactic matter between the two. At the AAO we have exploited this opportunity in two ways: in searches for very weak interstellar features requiring exceptionally high signal-to-noise ratio spectra, and in recording known interstellar lines with unprecedentedly high spectral resolution. We are also monitoring photographically the evolution of the light-echoes to map the three-dimensional distribution of interstellar matter near the supernova. Surprisingly high column densities of million-degree gas have been found in the LMC through the first detection of [Fe X] in absorption. The hot gas may fill the interior of a ‘superbubble’, created by the combined effects of previous supernovae in this active region of star-formation; this cavity may be related to the shells of interstellar matter giving rise to the light-echoes. The ultra-high resolution observations, which required the rapid construction of a dedicated new spectrograph, were successful in resolving the hyperfine structure of the sodium D lines in several interstellar clouds. This implies that the clouds are at temperatures of at most 170 K and have internal turbulent velocities of no more than 0.3 km s−1, even though some are moving with high velocities relative to the Sun.