It has been suggested (Holman et al 1980; Melrose and Dulk 1982a) that solar microwave spike bursts are due to electron cyclotron maser action. These bursts have been observed in the range 1-3 Ghz, and occur in conjunction with flare-associated impulsive microwave and hard X-ray bursts. The bursts have rise times of a millisecond or less (e.g. Slottje 1978).

There are two current models for the typical radio spectra of flare stars, which have a broad peak around a frequency typically 1 – 10 GHz. One model involves both optically thick and optically thin emission, with the turnover attributed to the source becoming self-absorbed. The other model involves only emission at optical depth unity, so that observing different frequencies corresponds to ‘seeing’ different regions in the source. The two models are reviewed, and new calculations for an inhomogeneous source presented.

A proposal for the siting of additional 14 metre antennas for the Fleurs Synthesis Telescope (FST) was previously presented by Christiansen (1976). Since that time, difficulties have arisen which preclude the use of two of the locations. In addition, solutions to the problems of data reduction for irregular antenna spacings have been found (Frater and Skellern, 1978; Frater, 1978; Frater, 1979). It has now been possible to choose the locations of the final antennas to optimise the performance of the array within broader geographic constraints — subject now to the availability of sites on ‘friendly’ land.

It has become recognized that the dominant mechanism in the formation of the cores of resonance lines in the solar spectrum is non-coherent scattering, e.g., Thomas (1957). A study, preliminary to the theoretical investigation of the spectra of chromospheric structures, is the evaluation of the effect of diffuse reflection and transmission by non-coherently scattering media.

The Sun being a highly ionized gas, the basic physical quantities most needed for understanding solar phenomena are temperature, pressure (or density), velocity and magnetic field, together with their variations in space and time. The general aim at Culgoora is to secure observations from which these quantities may be derived (insofar as is practicable) simultaneously over extended solar regions. To do this has involved the development and use of filters of high spectral and spatial resolution, the study of atmospheric seeing and ways of securing high-resolution observations, and the study of methods of analysing observations to yield the physical quantities needed.

Report on the latest developments in the modelling of Solar granules and in particular, the influence of various viscosity laws on the theoretical predictions, such as the velocity field, intensity modulation, degree of overshooting into upper stable layers and so on.

A morphological comparison between radar meteor survey data obtained at Ottawa (Millman and McIntosh, 1964) from 1958 to 1962 and that obtained from Christchurch (Ellyett and Keay, 1963) in 1960-61, confirms that the Daytime Arietid, Delta Aquarid meteor shower association is the most prominent feature of the annual activity. The data from Canada and New Zealand are easily reconciled as far as this activity is concerned and also for the weaker Eta Aquarid shower which, having a radiant at zero declination, is equally prominent in both sets of data. Furthermore, the data from both hemispheres is consistent with a forty per cent increase in overall activity during the second half of the year.

We resolve a conflict in the literature concerning the effect of induced Compton scattering on the propagation of radio waves through the electron–positron wind surrounding a pulsar.

We have just completed the observational stage of a 2·4 GHz survey of the Southern Galactic Plane, using the Parkes radiotelescope, between 238° ≤ l ≤ 365° and with a latitude range of at least |b| ≤ 5° (beamwidth ~9 arcmin). The survey details both continuum emission and linear polarisation down to rms noises of approximately 12 and 4 mJy/beam respectively. It is the most sensitive survey to date of the southern plane at this frequency and should nicely complement the Effelsberg northern plane surveys in addition to the recent southern surveys such as the 843 MHz MOST survey and the 5 GHz PMN survey. The total-power maps are now completed, and reduction of the polarisation data is still in progress. In addition to compact HII regions and extragalactic sources, we are detecting on our total-power images a considerable amount of large-scale structure, and a significant number of new SNR candidates and spur-like features.

We present the results of an analysis of the spectra obtained for a sample of 27 Am stars. We find evidence for the presence of groups amongst these stars and argue that all Am stars exhibit a pseudo–luminosity effect.

Instruments were flown on the Pioneer 6 and 7 spacecraft during 1965-66 to study the degree of anisotropy of cosmic radiation in the energy range 7.5-90 Mev/nucleón. The instruments record the cosmic ray fluxes from each of four contiguous ‘quadrants’ of azimuthal rotation of the spacecraft, for each of three energy windows 7.5-45 Mev, 45-90 Mev, and 150-350 Mev for alpha particles and heavier nuclei. In addition, the counting rate of all particles of energy >7.5 Mev is recorded, thereby providing cosmic ray data of high statistical precision useful in the study of fast changes in the cosmic ray flux.

The recent intensive study of Comet Halley based on in situ measurements, observations carried out with rockets and satellites and supplemented with co-ordinated Earth based observations has not only confirmed pre-Halley results, but also has given new insight into the nature of the nucleus, dust, gas and the interaction of cometary plasma with the solar wind. These observations also have raised many new questions and problems. Several of these aspects will be discussed. For a better understanding of these problems, the planned future missions to comets will also be discussed.

One of the two main telescopes at Sydney Observatory is a computer-controlled 35.6-cm Celestron. It is used with a television-type system. There is an integrating CCD camera available as well as an ordinary TV camera for bright objects. The images from the cameras can be shown in the Observatory’s lecture room. They are first put through an image processor which allows constant enhancement, spatial filtering and the recording of images for use on cloudy nights. Preliminary results are encouraging, and show the value of the system, even in Sydney’s highly light-polluted sky.

This paper summarises Ginga X-ray observations of SN 1987 A.

Numerical simulations suggest that colliding molecular clouds induce gravitational collapse and may be responsible for star formation. We incorporate magnetic fields in these simulations and present preliminary results of an investigation of the influence of magnetic fields on star formation via this process.

About 13% of bright galaxies are ellipticals (21% SO, 64% Spiral and Im, 2% IO and peculiar). Their obvious features are the smooth luminosity distribution and the near absence of the bright blue stars, HII regions and dust that appear in spiral systems; there is probably very little star formation going on at present in E galaxies. I plan to discuss some of the dynamical and physical properties of these systems; although many of them are known radio sources, I will not be able to discuss their radio properties.

Savage et al. (1977) found that the radio source PKS 1448-232 coincided with a stellar object of about magnitude 16.4 having an ultraviolet excess. A low resolution spectrum obtained with the Anglo-Australian Telescope (AAT) confirmed this object as a QSO with zem = 2.22 and revealed many absorption lines short-ward of the La emission. Consequently this object was included in a programme of spectroscopy at intermediate resolution with the AAT to investigate QSO absorption lines. Savage et al. have given a finding chart with an optical position of 14h48m09s.3, −23°17′10″ (1950.0). The radio fluxes are 0.40 Jy at 2.7 GHz and 0.31 Jy at 5.0 GHz.

Our recent papers have been devoted to basic studies of diatomic and polyatomic molecules (Singh and Chaturvedi 1989 a,b,c,d; 1990a,b,c). A critical analysis of the 456 available references in literature has been made to select 135 polyatomic molecules, molecular ions and radicals containing from three to thirteen atoms of astrophysical significance. The results have been arranged in a text-cum-tabular form (Singh and Chaturvedi 1989 b,d). The compilation contains various information for each molecule, such as the spectral region, transition levels, and astrophysical objects where the respective molecules have been detected (say, comet, meteorite, Sun, planet, star, interstellar medium. Galaxy, etc.).