The disk stellar luminosity function has been redetermined by the mean absolute magnitude method, utilising the proper motion data of the LHS Catalog. The derived luminosity function shows a slightly deeper dip than that found by Wielen (1983) in the same magnitude range.

The Chatterton Astronomy Department of Sydney University, in collaboration with the Astronomy Group of Imperial College (London), has carried out a program of speckle interferometry on the 3.9 m Anglo-Australian Telescope (AAT). Over 2 km of film were exposed during the two observing sessions in November and December, 1978, and the analysis of this very large amount of data is being carried out at the present time.

The arms in spiral galaxies cannot be material arms for then they would wind up on a time scale of one galactic rotation, or a few times 108 years. The large number of spirals suggests that the spiral pattern must persist for about 1010 years (or be continually rejuvenated). The density wave theory treats the spiral pattern as a wave phenomenon, thus overcoming this problem. Much work has been done studying small amplitude oscillations in flat stellar discs. Self-consistent spiral modes have been found, but they are not stable and grow at a fast rate. Numerical simulations of thin stellar discs, such as those of Hohl (1971), which can handle finite amplitude waves, have been more successful. Spiral waves form initially but evolve into a steady state rotating bar. It seems therefore, that a long-lived spiral cannot be formed in stars alone.

There is reasonably strong evidence to suggest that the periodic X-ray, radio and optical variable Cir X-1 is a highly eccentric orbit (e ~ 0.8), binary system comprising an OB supergiant primary and a compact object, probably a neutron star (Whelan et al. 1977; Haynes, Lerche and Murdin 1980).

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.

This paper presents results from speckle observations of binary stars carried out between 1987 and 1990 using a 212-cm telescope at the San Pedro Martir Observatory, Mexico.

Molonglo Observatory has played an important role in pulsar astronomy from shortly after the initial discovery announcement in 1968 to the present. Its major contribution has been in the area of searches for new pulsars – for most of the 17-year period more than half of the known pulsars were Molonglo discoveries. The history of pulsar astronomy at Molonglo is reviewed and a brief account of current observation programs is given.

This document is the final Phase A Science Report of the Australian LYMAN Science Working Group, and describes in detail the scientific objectives, technical feasibility, and engineering implementation of the LYMAN mission as developed in the Australian studies.

One of the important discoveries of astronomy is that the Universe expands: distant galaxies have large recession velocities in direct proportion to their distances. Attempts to determine a global value for the constant of proportionality between the velocity and the distance (Hubble constant) are met with difficulties by the presence of peculiar, random and streaming motions in the local region. These peculiar motions are either of primordial origin or the effect of density perturbations. These affect the mean velocity of the nearby groups in the level of 50-100 km/sec (Tammann, Sandage and Yahil 1980). However, the expected peculiar gravitationally induced motion of the Local Group towards the Virgo cluster, could be large due to the high density contrast in that direction (Sciama 1967; de Vaucouleurs and Peters 1968; Sandage, Tammann and Hardy 1972; Jones 1976). This infall motion could be as high as 500 km/sec if the anisotropy of the microwave background is interpreted to have a component of our peculiar motion towards the Virgo cluster (Peebles 1971, Boughn, Cheng and Wilkinson 1981; Gorenstein and Smoot 1981).

We present an overview of the survey for radio emission from active stars that has been in progress for the last six years using the observatories at Fleurs, Molonglo, Parkes and Tidbinbilla. The role of complementary optical observations at the Anglo-Australian Observatory, Mount Burnett, Mount Stromlo and Siding Spring Observatories and Mount Tamborine are also outlined. We describe the different types of star that have been included in our survey and discuss some of the problems in making the radio observations.

There is a large body of evidence to suggest that the anomalous OH emission sources—particularly those which are classified as class I sources—are associated with protostars. It is also known, from the theories brought forward over the past four years, that maser action can be caused by quite a variety of non-equilibrium situations. It is argued here that one particular kind of non-equilibrium situation which can plausibly be expected to exist in protostars is very similar to that proposed previously in the electron-pumping model, and that, in this new context, it can mimic most of the observed features of class I sources.

We have recently discovered evidence for a population of radio-loud quasars that is reddened by dust. The dust is either along the line of sight to the quasars or is associated with the quasars. In the latter case the dust may be in molecular clouds in the quasar’s host galaxy, or in a molecular torus around the nucleus. We are planning to use 3 mm observations to search for molecular absorption lines (CO and HCO+) associated with dust at the redshift of these quasars. If any absorption systems are detected we will be able to deduce detailed information about the physical state of the molecular gas, hopefully showing which of the proposed locations of the dust is most likely.

Ground-based observations of Jupiter’s decametric radio emission (DAM) have been reviewed by Ellis (1965), Warwick (1967, 1970) and Carr and Gulkis (1969). A startling feature of DAM is the modulating effect of Io, and interpretation of the Io effect has dominated theoretical discussions of DAM until quite recently, specifically until the fly-by s of Voyagers 1 and 2. The Voyager data showed that the DAM appears as nested arcs in the frequency-Jovian longitude plane (Warwick et al. 1979, Boischot et al. 1981). The interpretation of this arc structure has been of primary theoretical interest over the past two years. The most widely adopted explanation is that the emission from each point is confined to the surface of a hollow cone (Goldstein and Thieman 1981). This idea is not new: emission on the surface of a cone was discussed by Ellis and McCulloch (1963); Dulk (1967) derived detailed parameters for the cone (half angle 79° width 1°) from the occurrence pattern of DAM; and Goldreich and Lynden-Bell (1969) presented a theoretical interpretation of it. More recently Goldstein et al. (1979) used observational data on the Jovian magnetic field in deriving properties of the required emission cone. It seems that one requires the properties of the emission cone to vary with position in the Jovian magnetosphere to account for the nested arc pattern (Goldstein and Thieman 1981; Gurnett and Goertz 1981).

This paper reports results from a graded shield X-ray telescope experiment flown from Mildura, Australia on 29 February 1968. The experimental equipment also included the actively collimated telescope previously described. Certain preliminary results from this flight have been described elsewhere.

It has been suggested that diffuse X-ray sources observed in globular clusters may arise in bow shocks formed by the interaction of intracluster gas with a tenuous halo medium. This paper presents a study both of the cluster space motions and of the energetics of any possible bow shocks which would seem to rule out this hypothesis.

Solar flares for which protons of relativistic energies reach Earth are rare events compared with the number in which non-relativistic protons are produced. For instance, Shea and Smart (1978) have listed 139 proton events for the interval 1955-69 of which 17 were GLE’s (i.e. “ground level events” detected by the world network of cosmic ray neutron monitors). We have tentatively identified a further 11 GLE’s in the interval 1970-1977, of which 3 were in 1977 in the sunspot cycle which commenced about mid-1976 (cycle 21). Thus the average rate over the past two solar cycles has been a little over one per year.