Recent 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).

A substantial population of red quasars has been discovered in a complete sample of flat-spectrum radio sources. Dust is the most likely cause of the reddening in this sample. The location of the dust is poorly known, but may either be in the line-of-sight to the quasar, or in the immediate quasar environment. In this paper we are interested in models where the dust is located in the line of sight to the quasar. We calculate the probability distribution of the optical depth in galactic dust as a function of source redshift, using a range of parameters which might describe real galaxies. We compare these results with those found for our sample of radio quasars. If the dust content is unevolving, then it is not possible to account for all the observed reddening in the quasar sample using these models. Our minimum dust model predicts that 15% of background quasars to z ~ 5 will have a line of sight within 5 kpc of a galaxy’s centre, and would therefore be reddened out of B-band flux-limited samples.

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

A long-standing problem in the theory of astrophysical accretion disks has been to determine the nature of the stress that transports orbital angular momentum outward. The discovery of a local MHD instability is strong evidence that transport occurs through turbulent Maxwell and Reynolds stresses. Using numerical simulations, we have demonstrated that a weak seed magnetic field in an accretion disk shear flow is unstable and leads to sustained MHD turbulence at dynamically important levels.

The 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 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.

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

This paper discusses problems which have as their uniting theme the need to understand the coupling between a stellar convection zone and a magnetically dominated corona above it. Interest is concentrated on how the convection drives the atmosphere above, loading it with the currents that give rise to flares and other forms of coronal activity. The role of boundary conditions appears to be crucial, suggesting that a global understanding of the magnetic field system is necessary to explain what is observed in the corona. Calculations are presented which suggest that currents flowing up a flux rope return not in the immediate vicinity of the rope but rather in an alternative flux concentration located some distance away.

Ultracompact H II regions are small, dense regions of ionised gas surrounding high-mass stars which are still embedded in their natal molecular clouds. A survey of such regions has been commenced in an attempt to improve our understanding of the processes of high-mass star formation. The initial stages of the survey have involved selection of likely candidates from the IRAS Point Source Catalogue, correlation with radio continuum emission at 4·85 GHz and subsequent observations of methanol maser emission at 6·668 GHz. Preliminary results of the methanol maser survey are given.

It 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.

The 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.

Relative 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.

Radio 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.

The X-ray Timing Explorer (XTE) is a NASA satellite designed to perform high-time-resolution studies of known X-ray sources. The two main experiments are a large-area proportional counter array (PCA) from the Goddard Space Flight Center (GSFC) and a high-energy X-ray timing experiment (HEXTE) from the University of California at San Diego (UCSD). The PCA data is processed by an electronic data system (EDS) built by the Massachusetts Institute of Technology (MIT) that performs many parallel processing analysis functions for on-board evaluation and data compression. MIT also provide an all-sky monitor (ASM) experiment so that XTE can be slewed rapidly to new transient sources. The spacecraft provides a mean science telemetry rate for the PCA of ~20 kilobits per second (kbps), with bursts to 256 kbps for durations of 30 minutes. Photons are tagged to 1 μs and absolute timing should be better than 100 μs. XTE is due for launch in late August 1995 and the first NASA Research Announcement (NRA) is due out in January 1995. This paper summarises XTE’s performance and then discusses the interactive and flexible operations of the satellite and some of the science it can do. These features should make XTE a productive spacecraft for coordinated observation programs.

Radio 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.

We have developed an easy-to-use, mouse-driven program for the interactive fitting of interstellar absorption lines in high-resolution astronomical spectra. The program, Xvoigt, gives values for the column density and velocity dispersion of the absorbing clouds. It runs under the popular X Window system available on most workstations, and offers significant enhancements over existing profile-fitting software. Xvoigt can be an important adjunct to automatic programs for fitting absorption lines in low to moderate signal-to-noise QSO or other spectra, and is ideal for demonstrating the details and difficulties of absorption line analysis.

The 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.

A 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.

This paper is based on a report given at the ASA Conference in July 1994, but takes account of subsequent developments up to the end of the year. The present state of the Two-degree Field (2dF) project for the AAT is reported. Good progress is being made on all fronts but some slippage has occurred, so that the instrument is now expected to begin astronomical observations only during the second half of 1995. An outline of other current and future instrumentation plans at the AAO is given.