Following 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.

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.

An acousto-optical spectrograph (AOS) with a high spectral resolution of 28 kHz has been developed for spectral line observations of objects, such as dark clouds, where the line-widths are low. It has been mounted on the 4-m-diameter millimetre-wave telescope at CSIRO Division of Radiophysics at Epping, NSW and successfully tested using 115 GHz Co observations of a sample of southern dark clouds. At 115 GHz the velocity resolution is 0.07 km s-1.

We present the results of an examination of low-resolution IUE spectra of Galactic planetary nebulae in an effort to determine the occurence of stellar winds in their central stars. Our analysis confirms the results obtained in previous studies.

The spectrum of a symbiotic star consists of an M-type absorption spectrum, a B-type shell spectrum and nebula emission lines, the relative contributions of these three components varying with time. The light curves of the symbiotic stars vary with a semi-regular period typically 200-800 days while larger eruptions occur on a timescale of ~ 3.5 years. Some suggestions which have been advanced to explain the combination spectrum, variability and eruptive behaviour of the symbiotic stars are:

1. (a) the symbiotic stars are binaries consisting of a hot and cool component.

2. (b) the symbiotic stars consist of a single hot star surrounded by a large optically thick envelope giving the appearance of a hot continuum with the absorption spectrum of a cool star superimposed on it.

3. (c) the symbiotic stars are single stars surrounded by a shock wave heated chromosphere.

   Although some of the symbiotic stars are undoubtedly binaries (for example, T Coronae Borealis), observatienal evidence suggests that others may be explained by hypothesis (c) above. The calculations described below provide an explanation of the symbiotic stars in conjunction with hypothesis (c).

A recent study has indicated that a substantial fraction of young pulsars born in supernovae have travelled outside the boundaries of their corresponding shell supernova remnants. A simple model suggests that this should not be the case, implying either that some postulated pulsar/remnant associations are false, or that pulsars are particularly difficult to detect until they have emerged from their remnants.

In designing a stellar spectrograph, it is pointless to exceed the resolving power necessary to obtain all the information from the spectrum of a star. This is limited mainly by atomic thermal motions, giving rise to the Doppler broadening of spectral lines, by turbulence and rotation of the stellar atmospheres in which the lines are formed, and by collisional broadening.

Altogether 26 new Herbig-Haro (HH) objects have been discovered by slit spectroscopy and narrow-band CCD imagery. Several of them are very remarkable in various aspects. We have also found a total of over 1000 HH candidates in L1641, L1630 and NGC 2264 on deep Schmidt plates. Fibre spectroscopy is currently underway, confirming already some 70 HH objects. Implications of this large number are briefly discussed.

Recently the possibility has been raised of using general relativistic star clusters as models for quasi-stellar sources. The theory of static, spherically symmetric, collisionless star clusters has been developed within the framework of general relativity. In particular, analogues have been found of the Newtonian polytropic models and of Woolley’s truncated Maxwellian systems. However, in view of the importance of rotation on stability in relativistic astrophysical problems, it is of considerable interest to include the effect of rotation in relativistic stellar dynamics.

A 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.

At optical wavelengths NGC 4945 is a nondescript edge-on spiral galaxy, much of which is obscured by dense dust clouds. However, at longer wavelengths a prominent nucleus is exposed which possesses both Seyfert and star-burst characteristics. Microwave observations highlight dense molecular clouds located near the nucleus. The large velocity range of these clouds lacks an adequate interpretation.

The concept of a national centre for the analysis of archival and contemporary space astronomy data has been identified as a highly desirable objective by the Australian astronomical community for a number of years. With the approaching launch of the Hubble Space Telescope (HST), the time is now appropriate to actively pursue this objective. HST will generate a data archive of unique astrophysical significance over the course of the ≥ 20 year mission. It is essential that Australian astronomers have efficient access to this resource, both to maintain our position at the forefront of astronomical research, and to complement our major ground-based facilities (particularly the AAT and the Australia Telescope). An Australian facility would provide efficient access to HST data and also to the analysis tools and expertise necessary for utilizing the data. Archival data from other NASA and ESA missions could also be supported, and in the longer term, the facility could become the science centre for the Lyman/Quasat missions.

This paper presents the case for an Australian Space Astronomy Data Centre, reviews the astronomy missions of relevance, and addresses the role, scope and implementation timescale of the facility. Preliminary estimates are given for the resources that will be required, and possible routes for funding the centre are outlined. Above all, the report is intended as a Discussion Paper to promote further consideration of the concept and of the service that could be provided to the Australian astronomical community.

A modern coudé spectrograph for observing the spectra of stars and planets with maximum efficiency is a complex and versatile instrument, which represents an investment about equal to that for a 40-inch telescope. The trend toward special telescopes for special kinds of work began in the 1930s with Schmidt telescopes for wide angle photography, and has been followed by the use of specialized telescopes for photoelectric photometry, and more recently by telescopes for polarization measurements. Two telescopes designed for exclusive use with coudé spectrographs already exist—the 48-inch at Victoria and the 60-inch at Haute Provence. More are needed, particularly in the southern hemisphere.

Cen X-3 was first discovered by Chodil et al. Since then, observations using the UHURU satellite have shown it to be an X-ray pulsar, and it must now have become one of the most searched for objects in the sky. It is both an X-ray pulsar (P~4.8 secs) and an X-ray eclipsing binary (P~2.08712 days).

A 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.

Type I radio bursts, as distinct from the continuum component frequently associated with them in a solar storm, are short-lived (0.1-2 s), narrow-band (2-10 MHz) bursts with frequency drift rates from 0 to 20 MHz s−1. They come from coronal regions close to the corresponding plasma levels, i.e. the frequency of radiation ω is close to the local plasma frequency ωp. They occur more frequently at frequencies above ~100 MHz but at times extend to frequencies as low as 20 MHz. Their observed equivalent brightness temperatures are usually about 109 K but they can reach 1011 K or higher. Except for an average decrease in polarization towards the limb and except for initial stages of a storm, type I bursts are strongly circularly polarized (approaching 100 per cent) in the sense of the O-mode.

At the centre of the Parkes 64—m radio telescope a region of diameter 17 m has recently been resurfaced to improve its efficiency at high frequencies. The first measurements using this section have been made at 22 GHz, in observations of both continuum sources and water tfapour masers. For these observations the receiver front-end used a mixer cooled in liquid nitrogen, followed by a 5 GHz cryogenic parametric amplifier as a second stage. The option of switching against an offset horn was available and the total systemnoise temperature was ∽ 750 K.

One of the main reasons for pursuing a gravitational as opposed to a magnetic theory is that there exist galaxies which seem devoid of gas and yet show unmistakable structure. These galaxies are among those classified as SBO2/3 to SBa(r), and I shall, after Curtis, call them theta galaxies. Examples are: NGC 1512, 1291,4693, and 2859. The theta galaxies gradually merge into ringed bar galaxies, which in turn merge into ordinary spirals.