The Teff (effective temperature) scale for M dwarfs is very uncertain. One method which can be used to establish this scale is to compare observed spectra to synthetic ones derived from appropriate model atmospheres. With this method the adequacy of the model atmosphere is of great importance and simple models can give incorrect results. Alternatively if the Teff scale is known with some accuracy then this comparison is a good test of the adequacy of the models. We have computed some new and preliminary model atmospheres for late type dwarfs which accurately treat the line opacity with the opacity sampling technique and employ laboratory values for the transition strengths of molecular bands. With the above two considerations in mind we compare the fluxes of these models to observed fluxes of late K and early M dwarfs. This preliminary analysis indicates a discrepancy with the currently accepted Teff scale for early M dwarfs with the models suggesting values some 200 K hotter.

A list of 901 radio sources with positional accuracies better than 0.5 arcseconds has been prepared from seventeen lists of radio source positions found in the literature. This compilation includes all such sources south of declination + 48° (the northern declination limit of the Compact Array of the Australia Telescope National Facility). Where available, optical identifications, optical magnitudes and redshifts are given as well as total-power flux densities.

We discuss a generalisation of the synchrotron bubble model which has been applied to short-lived radio transients which can peak and decay over just a few days. The assumptions of the simple model imply that when the flux is increasing with time, it must also be an increasing function of frequency. Observations of two recent radio transients, Nova Muscae 1991 and the Galactic Centre Transient, include the first data showing such a rising phase, and in both cases the radio flux was a decreasing function of frequency during the observed rising phases. Thus the simple synchrotron bubble model is inadequate, at least for these events. A fundamental feature of the simple model is the assumption that the process accelerating the radiating electrons ceases before the radio emission can escape. We relax this assumption by including an injection of electrons, with a constant energy spectrum, into the synchrotron bubble.

Simple hydrostatic equilibrium models have been very successful at describing the physical conditions in hot coronal loops (T > 106 K). However, equilibrium models of cooler loops predict densities that are much lower than observed. We follow the evolution of a hot loop which undergoes a sudden reduction in heat input. The physical conditions in the cooling loop show significant departures from equilibrium. Such models appear to be able to reproduce the physical conditions observed in intermediate temperature loops (105 < T < 106 K).

Who discovered QSOs? What was the first QSO discovered? To Maarten Schmidt (1963) goes the credit for realising that the emission lines he saw in a 13 mag star were the Balmer series in hydrogen at a redshift of 0.158. The first QSO had been recognised. But discovery is a complex process. Schmidt observed the ‘star’ because it was associated with a radio source 3C 273 by means of an accurate radio position. This was the first of several instances where accurate radio positions have enabled significant progress in the QSO story.

An improved model of the generation and propagation of cyclotron-maser radiation in flaring loops is discussed, which incorporates competition between driving of the maser instability and maser-induced relaxation of the unstable plasma. This model enables previous large discrepancies between the build-up, relaxation, and observed timescales to be resolved for solar microwave spike bursts. Also, it implies that emission via fundamental o-mode and second-harmonic x-mode instabilities can compete more effectively against fundamental x-mode emission than has previously been thought. Propagation of the radiation to the observer is discussed both theoretically and with reference to ray tracing calculations and it is shown that the observed levels of MHD waves in the corona make it significantly easier for the radiation to escape than in the unperturbed case. In the absence of nonlinear processes or mode conversion we argue that the escaping radiation is generated by either fundamental o-mode or second-harmonic x-mode instabilities.

A small radio astronomy group led by S.E. Williams in the Department of Physics at the University of Western Australia operated in the pioneering days. Observations were made of solar radiation at 75 Mc/s (4 m), using a polar-mounted Yagi antenna on the University campus in the Perth suburb of Nedlands. The group produced four papers, three in Nature and a longer one published locally. Although the work was noticed internationally, its influence on the course of radio astronomy seems to have been slight, and even the existence of the group has been almost forgotten outside of its home department.

The bright radio emission from flare stars has three characteristic properties: high brightness temperature, high degree of circular polarisation and rapid temporal variations. Two proposed emission mechanisms, electron cyclotron maser emission (ECME) and plasma emission, are compared and contrasted. It is argued that although the important features of the emission can be explained in terms of either ECME or plasma emission, all three favor ECME. However, the escapes of the radiation through the second harmonic absorption layer remains inadequately understood, and as a consequence doubts about the ECME interpretation remain.

Over past decades many attempts have been undertaken to detect a statistically significant 11-year variation in tree-ring widths and thereby provide direct evidence for the influence of solar cycle activity on growth. The data were generally associated with arid sites and were found to contain no signal of any consequence at the equivalent frequency. However, our recent analysis of a tree-ring chronology established from spruce trees growing at a very high sub-alpine site in Colorado, has revealed the presence of a dominant 11-year spectral periodicity over the last 200 years. These growth cycles could arise from temperature changes due to variations in insolation and climate or from variations in direct radiation within a specific band.

Charles Todd was the first Government Astronomer and Superintendent of Telegraphs in South Australia. Most widely known for his instrumental role in the construction of the Overland Telegraph, linking Australia and England, Todd also established the Adelaide Observatory and made valuable contributions to both astronomy and meteorology.

The effects of the specific geometry of the magnetic field (such as field lines with torsion) on curvature emission and absorption in pulsar magnetospheres are discussed. Curvature maser emission can arise from two effects: the curvature drift, as has already been discussed in the literature, and field line torsion as discussed here in detail for the first time. Maser emission due to field line torsion can operate only when the Lorentz factor is larger than a certain value. However, when the Lorentz factor of electrons or positrons is sufficiently high, curvature masering is due to both curvature drift and magnetic field line torsion. The optical depth in the case of field line torsion is estimated. It is shown that if torsion is due to rotation, the resultant luminosity should be dependent on the rotation period in such a way that shorter periods correspond to larger luminosities.

To present-day astronomers the name of Robert Ellery, by which our newly established lectureship is to be known, means little. A century ago it was a different story. Ellery was then one of the most respected scientists in the country, a leading astronomer who had been director of the Melbourne Observatory since it was founded in 1853, and who had taken it to a prominent position in international astronomy. Besides this he was a man of parts who spread his talents widely. He was a founder and long-term president of the Royal Society of Victoria, treasurer of the University Council, chairman of the committee of the Alfred Hospital, Trustee of the Public Library, the Art Gallery and the Museum, and he was an active member, latterly commander, of the local Torpedo and Signal Corps, a coastal defence unit manned by citizen soldiers. Late in life he became the first president of the Beekeepers’ Club. He was elected to the Royal Society and awarded a CMG: all in all, a man of character and achievement.

Results 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.

We present spectropolarimetric observations of the type Ia supernova 1992A obtained 2 weeks and 7 weeks after maximum light. No significant polarisation was detected across any of the spectral features.

In March 1963 a paper by Hazard, Mackey and Shimmins in Nature, announced an accurate position for the radio source 3C 273. This was subsequently identified as the first known quasar. Through an innocent editorial mistake, the affiliation of the first author was wrongly attributed. This caused long-term animosity between the Physics Department of the University of Sydney and the CSIRO Division of Radiophysics.

The technique of aperture synthesis is well developed in radio astronomy. When applied to the optical regime, aperture synthesis allows one to partially overcome the blurring effects of the atmosphere and increase the angular resolution of large telescopes to the diffraction limit.

MAPPIT (Masked APerture-Plane Interference Telescope) is a multi-element interferometer which operates at the coude focus of the 3.9 m Anglo-Australian Telescope. This instrument has recently been reconfigured to operate in a dispersed mode so that simultaneous observations in a band of wavelengths are possible. We will discuss this instrument’s new mode and present observations of the double star δ Sco and an angular diameter of the previously unresolved red giant β Gru.

The Edinburgh-Cape Bright QSO Survey is a very small sub-set of the Edinburgh Cape Blue Object Survey, which is a major survey to discover blue stellar objects brighter than B~18 in the southern sky. It will cover an area of sky of 10,000 square degrees with |b|>30 and dec <0. The blue stellar objects are selected by automatic techniques from U and B pairs of UK Schmidt Telescope plates scanned with the COSMOS measuring machine. Follow-up photometry and spectroscopy is being obtained with the SAAO telescopes to classify the types of objects brighter than B=16.5, with some of the more stubborn objects being subjected to AAO service spectroscopy. Some preliminary results for the 6% QSO minority are presented in this paper and comparison is made with the Palomar-Green QSO Survey in the north, which we find to be at least a factor of two incomplete.