Compact radio sources have been observed over several years at 2.3 GHz by interferometers of the NASA-JPL Deep Space Network with trans- or inter-continental baselines to study the secular behaviour of fine structure appearing in these sources. A comparison of the variation in flux density of components of diameter < 0.001 arcsec with the corresponding variation in total flux density of the source at the same frequency indicated that variations could be wholly ascribed to components of this order of magnitude.

In April 1967 the British and Australian Governments agreed jointly to build and operate a 150-inch (3.8m) optical telescope on Siding Spring Mountain, 16 miles west of Coonabarabran, N.S.W., where the Australian National University has an established observatory. To direct the construction and subsequent operation of the new telescope it was decided to create a statutory authority to be known as the Anglo-Australian Telescope Board. Pending the formation of this board, the two Governments, acting through the Department of Education and Science in Canberra and the Science Research Council in London, set up a joint policy committee to initiate the project.

The Molonglo Observatory synthesis telescope has been used to obtain twelve observations of a 23′ arc field containing the active star AB Dor. On each occasion, an unresolved source close to the optical position of AB Dor was observed. The source exhibits day-to-day variations of flux density, with a mean value of ∼4 mJy. The identification of the source with the star and the variations in emission are discussed.

In a previous paper it was shown how one could improve upon the Böhm-Vitense model of the solar convection zone by the inclusion of four different length scales and by the determination of these length scales with the use of the quasi-Vitense model as developed by Unno. In this way the vertical wave number kz, associated with a characteristic eddy, can be determined by the integration of a second order differential equation. The integrations have to be started at a suitable depth and all model calculations depend critically on the assumed structure of the top layer.

Current evolutionary theory indicates that evolving stars in globular clusters arrive on the horizontal branch with ~30% less mass than they had on the main sequence. If, as seems likely, this mass loss results from the outflow of unprocessed material at the stellar surface during the giant stage, and if the ejected mass were retained within the cluster between successive sweeps through the galactic plane (~108 yr), sufficient hydrogen (100-2000 M⊙ should accumulate for detection. Radio searches, however, have failed to find evidence for either neutral or ionized gas. The hydrogen mass upper limits obtained by various workers are: Hills and Klein (1973) ionized H, 3.8 cm, <20-200 M⊙; Knapp, Rose and Kerr (1973) neutral H, 21 cm, <1-20 M⊙; Conklin and Kimble (1974) neutral H, 21 cm, <0.7-1.4 M⊙.

We have extended the search into the optical region and have also calculated time-independent gas flow models to try to resolve this anomaly.

AAT/WFI optical images of a candidate extragalactic HI cloud, HIPASS J1712–64, are presented. The g and r band CCD mosaic camera frames were processed using a new data pipeline recently installed at the AAO. The resultant stacked images reach significantly deeper levels than those of previous published optical imaging of this candidate, providing a detection limit Mg ˜ −7 at a distance of 3 Mpc, the inferred distance to HIPASS J1712–64. However, detailed analysis of the images fails to uncover any stellar population associated with the HI emission. If this system is a member of the Local Group then it is pathologically different to other members. Hence, our observations reinforce earlier suggestions that this HI cloud is most likely Galactic in origin and not a Local Volume dwarf galaxy.

The study of short time scale phenomena of astronomical interest is often handicapped by the presence of wide band noise. In particular, in the study of the optical variability of stars, such noise arises from atmospheric scintillation, extinction variations, sky radiance variations and photon statistics. For example if in order to resolve rapid stellar variability we reduce the length (T) of the time intervals over which a photometric record is integrated and sampled, we find that the fractional noise fluctuations increase, eventually obscuring any intrinsic variability.

The Mount Stromio optical pulsar detection equipment is built around a commercial two-track tape recorder: one track records timing pulses, and the other the pulses from a photomultiplier (Peterson 1974). Because of the modest frequency range of the recorder, it has been necessary to introduce a scaler between the recorder and photomultiplier in order to cope with bright sources.

The eighth magnitude star HD 101065 has an extremely peculiar spectrum dominated by very numerous lines of the rare earths (with only the one possible exception of ytterbium, whose lines are difficult to identify). Besides the rare earths only strontium, yttrium and zirconium could be found in substantial quantities, while calcium though present is highly underabundant. The most surprising feature of the star is the absence of iron peak elements in its spectrum.

A grant from the Department of Employment, Education and Training and matching funding from the University of Western Sydney, Nepean, has allowed the construction of a teaching and public access observatory on the University’s Werrington North campus. The observatory consists of a lecture theatre for about 50 students, an office for administration and project/souvenir sales, and an enclosed office for research activities. The 6·5 m dome will house a fork-mounted 0·6 m (24 inch) Ritchey-Chrétien telescope working at f/10. There will also be two outside observation areas for tripod-mounted telescopes. The expected completion date for the entire project is mid-1994.

A 3 GHz maser from the Onsala Space Observatory, Sweden, is currently at Parkes on a long-term loan basis. So far, it has been used on the 64-m radio telescope for a two-week period of spectral-line observations in February 1979, providing a system sensitivity far superior to that previously available at the same frequency. The observed lines were the ground-state transitions of CH at 3264, 3335 and 3349 MHz, the 211 – 212 transition of H2CS at 3139 MHz, and the 211-212 transition of CH3CHO at 3195 MHz.

The causes of various traits of the polar motion are still unknown or uncertain. For exploring these the Chandler nutation has the advantage of being readily observable and it should be independent of external torques. This nutation shows a prograde motion of the earth’s axes of rotation and of excitation about each other. For simplicity the positions of the poles of rotation P and excitation ψ (Munk & MacDonald, 1960) are given in terms of dimensionless excitation functions which apply in principle whether they come from distributions of mass, relative motions or torques. Let O be the pole of zero excitation and R be the angular distance between P and ψ.

The energy passing through the boundaries of a convective zone in a star, in an outward radial direction per second, must in total be equal to the luminosity of the star, provided of course that this zone does not encompass nuclear energy producing regions. If, in an endeavour to establish the nature of the convective motions in this zone, a section of the zone is modelled by considering steady cellular convection in a horizontal layer of Boussinesq fluid, it is on the basis of an average energy flux being imposed. Moreover, the sum of the conductive and convective heat fluxes is represented by the Nusselt number, which is specified and constant for the zone.

Rich clusters of galaxies are a common feature of the large-scale structure of the Universe. Those studied so far, show striking regularities with

1. (a) a smooth radial gradient of number density.

2. (b) ’isothermal’ distributions, which according to Bahcall (1975) have a scatter of only ±15% in the size of their characteristic core radii.

3. (c) their limiting structural diameters are ~50 Mpc (cf. Abell, 1975), if they are identified with superclusters.

4. (d) the magnitude of the velocity dispersion about their centres is generally 600-1000 km s-1, and the velocities are cpnsistent with a gaussian distribution (Yahil and Vidal, 1976; also Faber and Dressier, 1976).

5. (e) The extreme velocities are generally within ±3000 km s-1, and for Coma are ∼2400 km s-1 (Tifft and Gregory, 1976).

6. (f) elliptical galaxies tend to predominate near the centre, spirals in the surrounding loose groups.

A departure from an isothermal mass distribution in a rich cluster is expected if the genesis involves a coherent recollapse phase. The character of this departure is calculated and looked for in the data available for the Comma Cluster. No significant deviation from an isothermal mass distribution is found for r < 360’.

The Fleurs Synthesis Telescope (FST) has been used to map a number of bright, southern galactic HII regions at 1415 MHz. Descriptions of the FST can be found in Christiansen (1973) and associated papers. For the observations reported here, both the east-west and the north-south arms of the cross were used resulting in beamshapes which are nearly circular with half-power widths of 50” arc. The maps have been “cleaned” using a standard process (Högbom 1974).

One of the major problems in the theory of type III solar radio bursts concerns the development of the two-stream instability. On the one hand, Sturrock (1964) argued that one expects the instability to develop rapidly, and if it does it should prevent the stream from propagating through the corona, contrary to observation. On the other hand, one appears to require that the instability develop partially, in the sense that there is some significant amplified emission of Langmuir waves, in order to account for the observed emission.

The most sensitive X-ray survey available is a deep exposure made by the Einstein Observatory of a 40 arcmin field in the southern constellation of Pavo. This survey revealed 33 X-ray sources, most of which were optically identified with quasars. Here, we report radio observations of the Pavo region at 843 MHz made with the Molonglo Observatory Synthesis Telescope. Eight overlapping fields were combined to produce the most sensitive radio map of the region to date, revealing 33 radio sources above a flux density of 2.4 mJy. Only one of these radio sources corresponded to an X-ray object: a quasar at z = 1.13. We also used the Parkes-Tidbinbilla Interferometer, at 2.29 GHz and 8.41 GHz, to observe some of the stronger radio sources.

From these multi-wavelength observations of the Pavo field it is apparent that, to the sensitivity of the surveys involved, (i) there is little correlation between X-ray and radio detections, and (ii) most of the X-ray sources have optical counterparts while few of the radio ones do, and (iii) there is some confirmation that X-ray emission is higher for objects with flat radio spectra (i.e., a dominant core) than for steep spectrum sources.

In this paper I examine the use of optical and UV spectral diagnostic ratios to distinguish between gas which is locally shock-excited by the interaction with a jet and that which is photoionised by the central engine. In many cases key UV lines remain unobserved except in the case of high redshift radio galaxies. However, in one case, the nearby GPS galaxy NGC1052, UV data was obtained with the FOS. This object shows LINER characteristics at optical wavelengths, but has a rich coronal-line spectrum in the UV. We conclude that jet-driven shocks tend to evolve from shock-excited to photoionised later in their evolution.

Large outbursts from the Sun which are widely extended over centimetre and decimetre ranges and show smooth time variations in intensity have been called microwave type IV bursts (μ-IV). Those bursts generally consist of more than two successive components, the spectra of which move progressively towards the lower frequencies. Furthermore there is a tendency for the decay times, which are defined as the times occupied by the decreasing parts of the bursts, to become successively longer. It seems worth while to make a quantitative study of the time variation of the decay times and flux densities of μ-IV burst spectra and to infer how the physical conditions in the source change with time.