The theory of coronal structure and of the associated angular momentum transport by magneto-thermo-centrifugal winds is reviewed, with reference to recent observations of rapidly rotating late-type stars. In particular, the combined optical and X-ray studies of AB Doradus are consistent with the predicted picture of a hot, magnetically-controlled ‘dead zone’ in near corotation with the star, and of cooler wind-emitting regions (analogues of the solar coronal holes). The standard theory predicts a rate of angular momentum transport that depends on the extent of the wind zone, the relative importance of thermal and centrifugal driving, and the variation of the dynamo-built surface field with rotation. For stars like the Sun, with approximately one tenth of the mass in the convective envelope, detailed comparison of the theory with the observed rotations of stars in clusters of different ages is sensitive to the strength of the coupling between the envelope and the radiative core, and is constrained by helioseismological limitations on rotational shear within the present-day Sun. An inferred strong braking during the early epochs may hint at a non-standard braking model, with the Maxwell stresses dominant far from as well as near the stellar surface.

The 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.

Among the most important stimuli for developing the FLAIR multi-object spectroscopy system on the 1.2-m UK Schmidt Telescope was its potential for carrying out large-scale redshift surveys of galaxies of intermediate magnitude (B <~ 17). During FLAIR’s lengthy development period, these objects provided the yardstick by which the system’s performance was measured, and a number of limited-area redshift surveys were carried out. We are now following these with a 1-in-3 survey over the 60 fields of the ROE/Durham Galaxy Catalogue to produce a redshift map of some 4000 galaxies out to a distance of ~ 300h−1 Mpc (where the parameter h is the Hubble constant expressed as a fraction of 100 kms−1 Mpc−1). In this paper we summarise the results from our redshift surveys to highlight the capabilities of FLAIR. We present a status report on the current large-scale survey, and show that the recently-introduced FLAIR II system will speed its progress considerably.

We present 6 cm Australia Telescope images of 22 strong southern radio sources. At least one of these sources appears likely to be a gravitationally lensed mirage.

strong non-thermal radio sources at low galactic latitude may be young galactic supernova remnants or else distant extragalactic objects located in the direction of the galactic plane merely by chance. Here, we have imaged G321.48 + 1.02 with the Australia Telescope in order to distinguish between these alternatives for this source.

Ina recent paper, Lockwood et al. (1991) have used IMP spacecraft and Neutron Monitor data to consider the rigidity dependence of three large Forbush Decreases over the energy range 50 MeV to 30 GeV. Some of their conclusions are extrapolated to higher energies.

In an earlier paper (Duldig, 1987a), one of us discussed the need to consider the presence of isotropic intensity waves when determining the Forbush Decrease spectrum at energies up to a few hundred GeV. Lockwood et al.’s conclusions are discussed in the light of these results.

In this paper the Very High Energy (VHE) gamma-ray astronomy program at the University of Adelaide is described. VHE gamma rays with energies above ~5 × 1011eV are observed using the atmospheric Cerenkov technique. Results from the first three years observations at Woomera and the current upgrading of the telecope are described. The CANGAROO project, a collaboration between the University of Adelaide and a number of Japanese institutions, is also introduced.

Mass-loss has been incorporated into a series of evolutionary calculations of low to intermediate mass stars during Asymptotic Giant Branch (AGB) evolution. When helium shell flashes occur a superwind phase is a natural consequence of the mass-loss process. The structure of the stellar wind envelopes that result has been computed. The models may explain some previously curious features seen in OH/IR and CO line emission spectra.

Some results of spot modelling for 18 light curves of AB Dor are presented, covering the period 1980-1992. Using the technique of Budding and Zeilik (1987) to determine spot parameters, it is shown that photospheric spots on this star tend to form in one of two longitude belts separated by approximately 180 degrees. This can be compared to the similar active longitudes proposed by Zeilik et al.(1988, 1989) for the RS CVn stars SV Cam and RT And. The change in overall light level of AB Dor over the past 12 years indicates the possibility of a solar-type spot cycle although more photometric observations will be needed to confirm this.

The reappearance of radio emission from SN 1987A is discussed. We propose a model involving synchrotron radiation from electrons which are accelerated when the expanding supernova shock wave runs into a density jump in the circumstellar material, and which then expand adiabatically.

Between the time when the shock approaches the outside of the progenitor star, when the shocked material is highly ionized, and a few months later, when the material has cooled and recombination is almost complete, details of the coupling of radiation and the hydrodynamics of the shock propagation may be significant, with a subsequent effect on the photosphere and thus spectra. I argue for the inadequacy of current analyses of shock breakout and of the customary adoption of self-similar expansion of an initial structure for spectral synthesis of the first few months, in place of a complete hydrodynamic simulation. Progress towards a full radiative hydrodynamic simulation including relativistic effects and detailed line opacities is discussed.

The absorption counterpart of curvature emission is reexamined based on the Landau-Lifshitz approach. Early derivations led to the conclusion that maser emission is not possible, but these early derivations neglected a drift effect which was first discussed by Zheleznyakov and Shaposhnikov. When the drift effect is included, the derivation implies that curvature maser emission is possible. It is shown that for maser emission to be possible, the Lorentz factor needs to satisfy γ ≳ 103 for radius of curvature of the magnetic field lines RB ≈ 106 to 109cm and frequency ω ≈ 107 to 1011 s−1. Possible application to pulsars is discussed.

When a rotating magnetised system (angular speed Ω), such as a planet or star, loses mass there is necessarily an energy dissipation associated with the mass loss. Consider mass loss at rate M, such that the matter is flung off with the orbital speed ΩR1, at a radius R1 ≫ R0, where R0 is the radius of the planet or star. The power released is approximately equal to the power Prot = 1/2MΩ2R2 carried off in rotational kinetic energy. Part of the energy released is carried off as magnetic energy in the escaping plasma, and the remainder is released through dissipation of currents. Such dissipation plausibly leads to the acceleration of particles. The power released should be important for Jupiter and for some rapidly rotating stars. For most stellar systems, the power released is small compared to that required to drive a wind.

We report on an initial survey of the cores of the Rho Ophiuchus and R Coronae Australis clouds, made with the AAT’s new IR array camera, IRIS. No turnover is seen in the initial luminosity function for ρ Oph to the sensitivity limit of the survey. Some implications for the low mass end of the initial mass function are discussed.

The AAT’S new IR array camera, IRIS, has been used to image the Galactic Centre in the He I (2.058μm), H+ Br γ(2.166μm) and H2 1-0 S(l) (2.122μm) emission lines. The case is presented for UV-excitation of the molecular gas, as opposed to shocks.

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).

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.

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.

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.

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.